Aluminium Casting Alloys - Aleris

Aluminium Casting Alloys


Aluminium Casting Alloys 


Content 

4 

Introduction 5 

Recycled aluminium 6 

Technology and service 

for our customers 

Quality Management 7 

Work safety and health 8 

protection 

Environmental protection 

Aluminium and aluminium 9 

casting alloys 

Aluminium – Material properties 

Recycling of aluminium 

Shaping by casting 10 

Product range and 11 

form of delivery 

Technical consultancy 12 

service 

Selecting aluminium 13 


Criteria for the selection of 14 

aluminium casting alloys 

Infl uence of the 18 

most important alloying 

elements on aluminium 


Infl uencing the 19 

microstructural formation of 

aluminium castings 

Grain refi nement 20 

Modifi cation of AlSi eutectic 21 

Refi nement of 23 

primary silicon 


Melt quality and melt cleaning 24 

Avoiding impurities 25 

Melt testing and 28 

inspection procedure 

Thermal analysis 30 

Selecting the casting process 31 

Pressure die casting 32 

process 

Gravity die casting process 

Sand casting process 34 

Casting-compliant design 35 

Solidifi cation simulation 37 

and thermography 

Avoiding casting defects 38 

Heat treatment of 40 


Metallurgy – 

fundamental principles 

Solution annealing 41 

Quenching 

Ageing 42 

Mechanical machining of 44 


Welding and joining 45 


Suitability and behaviour 

Applications in the 

aluminium sector 

Welding processes 

Weld preparation 47 

Weld fi ller materials 

Surface treatment: corrosion 48 

and corrosion protection 

Information on physical data, 50 

strength properties and 

strength calculations 

Notes on the casting 51 

alloy tables 

Overview: Aluminium casting 52 

alloys by alloy group 

Eutectic aluminium-silicon 59 


Near-eutectic wheel 63 


The 10 per cent aluminium- 66 

silicon casting alloys 

The 7 and 5 per cent 71 

aluminium-silicon 


Al SiCu casting alloys 76 

AlMg casting alloys 81 

Casting alloys for special 87 

applications

Introduction 

Many of you have most certainly worked 

with the “old“ Aluminium Casting Alloys 

Catalogue – over the years in thousands 

of workplaces in the aluminium industry, 

it has become a standard reference 

book, a reliable source of advice about 

all matters relating to the selection and 

processing of aluminium casting alloys. 

Even if you are holding this Aluminium 

Casting Alloys Catalogue in your hands 

for the fi rst time, you will quickly fi nd your 

way around with the help of the following 

notes and the catalogue‘s detailed index. 

How is this Aluminium Casting Alloys 

Catalogue structured? The catalogue 

consists of three separate parts. In the 

fi rst part, we provide details on our com- 

pany – a proven supplier of aluminium 

casting alloys. 

In the second part, all technical aspects 

which have to be taken into account in 

the selection of an aluminium casting alloy 

are explained in detail. All details are 

based on the DIN EN 1676: 2010 standard. 

The third part begins with notes on the 

physical data, tensile strength characteristics 

and strength calculations of 

aluminium casting alloys. Subsequently, 

all standardised aluminium casting alloys 

in accordance with DIN EN 1676 as well 

as common, non-standardised casting 

alloys are depicted in a summary table 

together with their casting/technical and 

other typical similarities in “alloy families”. 

The aim of this new, revised and redesigned 

Aluminium Casting Alloys Catalogue 

is to give the user of aluminium 

casting alloys a clear, well laid-out companion 

for practical application. Should 

you have any questions concerning the 

selection and use of aluminium casting 

alloys, please contact our foundry consultants 

or our sales staff. 

You can also refer to www.aleris.com. 

We would be pleased to advise 

you and wish you every success 

in your dealings with aluminium 

casting alloys! 


5

Recycled aluminium 

Technology and service for our customers 

Employing approx. 600 people, Aleris 

Recycling produces high-quality casting 

and wrought alloys from recycled 

aluminium. The company‘s headquarters 

are represented by the “Erftwerk” 

in Grevenbroich near Düsseldorf which 

is also the largest production facility in 

the group. Other production facilities 

in Germany (Deizisau, Töging), Norway 

(Eidsväg, Raudsand) and Great Britain 

(Swansea) are managed from here. With 

up to 550,000 mt, Aleris Recycling avails 

of the largest production capacities in 

Europe and is also one of the world‘s 

leading suppliers of technology and 

services relating to aluminium casting 

alloys. Aleris Recycling also offers a wide 

range of high-quality magnesium alloys. 

Aluminium recycled from scrap and 

dross has developed to become a 

highly-complex technical market of the 

future. This is attributable to the steady 

increase in demand for raw materials, 

the sustainability issue, increased environmental 

awareness among producers 

and consumers alike and, not least, the 

necessity to keep production costs as 

low as possible. 

This is where aluminium offers some essential 

advantages. Recycled aluminium 

can be generated at only a fraction of the 

energy costs (approx. 5%) compared to 

primary aluminium manufactured from 

bauxite with the result that it makes a 

signifi cant contribution towards reduc- 

ing CO 2 emissions. This light-alloy metal 

can be recycled any number of times 

and good segregation even guarantees 

no quality losses. 

6 


Its properties are not impaired when 

used in products. The metallic value is 

retained which represents a huge economic 

incentive to collect, treat and melt 

the metal in order to reuse it at the end 

of its useful life. 

For this reason, casting alloys from Aleris 

Recycling can be used for manufacturing 

new high-quality cast products such as 

crankcases, cylinder heads or aluminium 

wheels while wrought materials can be 

used for manufacturing rolled and pressed 

products, for example. Key industries 

supplied include: 

Rolling mills and extrusion plants 

Automotive industry 

Transport sector 

Packaging industry 

Engineering 

Building and construction 

Electronics industry 

as well as other companies in the 

Aleris Group. 

State-of-the-art production facilities and 

an extensive range of products made of 

aluminium in the form of scrap, chips or 

dross are collected and treated by Aleris 

Recycling before melting in tilting rotary 

furnaces with melting salt, for example, 

whereby the salt prevents the aluminium 

from oxidising while binding contaminants 

(salt slag). Modern processing and 

melting plants at Aleris Recycling enable 

effi cient yet environmentally-friendly re- 

cycling of aluminium scrap and dross. 

The technology used is largely based on 

our own developments and – in terms of 

yield and melt quality – works signifi cantly 

more effi ciently than fi xed axis rotary 

furnaces and hearth furnaces. The melt 

gleaned from these furnaces has a very 

low gas content thanks to the special gas 

purging technique we use as well as 

being homogeneous and largely free of 

oxide inclusions and/or contaminants. 

The resulting high quality of Aleris alloys 

enables our customers to open up an increasing 

number of possible applications. 

All management processes and the entire 

process chain from procurement 

through production to sale are subject to 

systematic Quality Management. Combined 

with Quality Management certifi ed 

to ISO/TS 16949 and DIN EN ISO 9001, 

this guarantees that our clients‘ maximum 

requirements and increasing demands 

can be fulfi lled. 

The product range offered by Aleris Re- 

cycling comprises more than 250 differ- 

ent casting and wrought alloys. They can 

be supplied as ingots with unit weights 

of approx. 6 kg (in stacks of up to 1,300 

kg) as well as pigs of up to 1,400 kg or 

as liquid metal. Based on our sophisticated 

crucible technology and optimised 

transport logistics, Aleris Recycling supplies 

customers with liquid aluminium in 

a just-in-time process and at the appropriate 

temperature.

Due to its future-oriented corporate 

structure, Aleris Recycling supplies the 

market with an increasing number of 

applications involving high-quality secondary 

aluminium. This service is not restricted 

to the area of casting alloys but 

also applies for 3000- and 5000-grade 

wrought alloys, for example. Aleris Recycling 

is also capable of offering some 

6000-grade secondary aluminium alloys 

largely required by the automotive sector. 

For this so-called upgrade, Aleris applies 

special production technologies when 

it comes to manufacturing high-quality 

alloys from scrap. 

Recycled aluminium is increasingly be- 

coming a complex range at the interface 

between high-tech production, trade and 

service. In addition, customers demand 

intensive consulting as well as individual 

service. Aleris Recycling enjoys an excellent 

position in this regard. 

At its various locations, the company 

units offer a high degree of recycling expertise, 

manufacturing competence and 

delivery reliability for its customers. With 

the result that Aleris Recycling guarantees 

its customers a high level of effi ciency 

and added value while supporting their 

success on the market. 

Quality Management 

We believe that our most important cor- 

porate goal is to meet in full our custom- 

ers‘ requirements and expectations in 

terms of providing them with products 

and services of consistent quality. In order 

to meet this goal, our guidelines and 

integrated management system specifi - 

cations outline rules and regulations that 

are binding for all staff. 

As a manufacturer of aluminium casting 

alloys, we are certifi ed according to ISO/ 

TS 16949. In addition, we operate according 

to DIN EN ISO 9001 standards. 

The principle of avoiding errors is para- 

mount in all our individual procedures and 

regulations. In other words, our priority 

is to strive to achieve a zero-error target. 

By effectively combating the sources of 

errors, we create the right conditions for 

reliability and high quality standards. 

We have also established a comprehen- 

sive process of continuous improvement 

(PMO, Best Practice, Six Sigma etc.) in 

our plants in response to the demands 

being placed on our company by the 

increasing trend towards business globalisation. 

This creates the right climate 

for creative thinking and action. 

All members of staff, within their own 

area of responsibility, endeavour to ensure 

that operational procedures are 

constantly improved, even if in small, 

gradual stages, with a clear focus on 

our customers‘ needs. 


7

Work safety and health protection 

Our staff are our most valuable asset. Work 

safety and health protection, therefore, 

have top priority for us, and also make 

a valuable contribution to the success 

of our company. Our “Work safety and 

health protection” programme is geared 

towards achieving a zero accident rate, 

and towards avoiding occupational illnesses. 

Depending on the respective 

location, we are certifi ed to OHSAS 

18001 or OHRIS. 

All management members and staff are 

obliged to comply with legal regulations 

and company rules at all times, to protect 

their own health and the health of 

other members of staff and, when engaged 

in any company operations, to 

do their utmost to ensure that accidents 

and work-related illnesses are avoided, 

as well as anything that might have a 

negative impact on the general company 

environment. Management provides the 

appropriate level of resources required 

to achieve these goals. 

There are regular internal and external 

training seminars on the topic of work 

safety, and detailed programmes to improve 

health protection. These help to 

maintain our comparatively low accident 

and illness rates. 

8 


Environmental protection 

Following the validation of our environ- 

mental management system in conformity 

with EMAS II and certifi cation to DIN EN 

ISO 14001, we have undertaken not only 

to meet all the required environmental 

standards, but also to work towards a 

fundamental, systematic and continual 

improvement in the level of environmental 

protection within the company. 

Our management system and environ- 

mental policy are documented in the 

company manual which describes all 

the elements of the system in easily 

understood terms, while serving as a 

reference for all regulations concerning 

the environment. 

The environmental impacts of our com- 

pany operations in terms of air purity, 

protection of water bodies, noise and 

waste are checked at regular intervals. 

By modifying procedures, reusing mate- 

rials and recycling residues, we optimise 

the use of raw materials and energy in 

order to conserve resources as effi ciently 

as possible. 

We pursue a policy of open information 

and provide interested members of the 

public with comprehensive details of 

the company‘s activities in a particular 

location, and an explanation of the 

environmental issues involved. For us, 

open dialogue with the general public, 

our suppliers, customers and other 

contractual partners is as much a part 

of routine operations as reliable co-operation 

with the relevant authorities and 

trade associations. 

Likewise, ecological standards are incorporated 

in development and planning 

processes for new products and production 

processes, as are other standards 

required by the market or society at large. 

Our staff is fully conscious of all environmental 

protection issues and is keen to 

ensure that the environmental policy is 

reliably implemented in day-to-day operations 

within the company.

Aluminium and aluminium casting alloys 

Aluminium – Material properties 

Aluminium has become the most widely 

used non-ferrous metal. It is used in the 

transport sector, construction, the pack- 

aging industry, mechanical engineering, 

electrical engineering and design. New 

fi elds of application are constantly open- 

ing up as the advantages of this material 

speak for themselves: 

Aluminium is light; its specifi c weight 

is substantially lower than other 

common metals and, at the same 

time, it is so strong that it can with 

stand high stress. 

Aluminium is very corrosionresistant 

and durable. A thin, 

natural oxide layer protects 

aluminium against decomposition 

from oxygen, water or chemicals. 

Aluminium is an excellent 

conductor of electricity, 

heat and cold. 

Aluminium is non-toxic, hygienic 

and physiologically harmless. 

Aluminium is non-magnetic. 

Aluminium is decorative and 

displays high refl ectivity. 

Aluminium has outstanding 

formability and can be 

processed in a variety of ways. 

Aluminium alloys are easy to cast 

as well as being suitable for all known 

casting processes. 

Aluminium alloys are 

distinguished by an excellent 

degree of homogeneity. 

Aluminium and aluminium 

alloys are easy to machine. 

Castings made from aluminium 

alloys can be given an artifi cial, 

wear-resistant oxide layer 

using the ELOXAL process. 

Aluminium is an outstanding 

recycling material. 

Recycling of aluminium 

Long before the term “recycling” became 

popular, recycling circuits already exist- 

ed in the aluminium sector. Used parts 

made from aluminium or aluminium alloys 

as well as aluminium residue materials 

arising from production and fabrication 

are far too valuable to end up as landfi 

ll. One of the great advantages of this 

metal, and an added plus for its use as a 

construction material, is that aluminium 

parts, no matter the type, are extremely 

well suited to remelting. 

The energy savings made in 

recycling aluminium are 

considerable. Remelting requires 

only about 5 % of the energy 

initially required to produce 

primary aluminium. 

As a rule, aluminium recycling 

retains the value added to the 

metal. Aluminium can be recycled 

to the same quality level as the 

original metal. 

Aluminium recycling safeguards 

and supplements the supply of 

raw materials while saving 

resources, protecting the 

environment and conserving 

energy. Recycling is therefore also 

a dictate of economic reason. 


9

The experience accumulated over many 

decades, the use of state-of-the-art 

technology in scrap preparation, remelting 

and exhaust gas cleaning as well 

as our constant efforts to develop new, 

environmentally-sound manufacturing 

technology puts us in a position to 

achieve the best possible and effi cient 

recycling rates. At the same time, they 

also help us to make the most effi cient 

use of energy and auxiliary materials. 

10 


Shaping by casting 

Casting represents the shortest route 

from raw materials to fi nished parts – a 

fact which has been known for fi ve thou- 

sand years. Through continuous further 

development and, in part, by a selective 

return to classic methods such as the 

lost-form process, casting has remained 

at the forefront of technical progress. 

The most important advantage of the 

casting process is that the possibilities 

of shaping the part are practically limitless. 

Castings are, therefore, easier and 

cheaper to produce than machined and/ 

or joined components. The general waiving 

of subsequent machining not only 

results in a good density and path of 

force lines but also in high form strength. 

Furthermore, waste is also avoided. As a 

rule, the casting surface displays a tight, 

fi ne-grained structure and, consequently, 

is also resistant to wear and corrosion. 

The variety of modern casting processes 

makes it possible to face up to the 

economic realities, i.e. the optimisation 

of investment expenditure and costs 

in relation to the number of units. With 

casting, the variable weighting of production 

costs and quality requirements 

are also possible. 

When designing the shape of the cast- 

ing, further possibilities arise from the 

use of inserts and/or from joining the 

part to other castings or workpieces. 

In the last decade, aluminium has at- 

tained a leading position among cast 

metals because, in addition to its other 

positive material properties, this light 

metal offers the greatest possible variety 

of casting and joining processes.

Product range and form of delivery 

As ecological and economic trends sensibly 

move towards the development of 

closed material circuits, the clear dividing 

lines between the three classic quality 

grades of aluminium casting alloys are 

ever-decreasing. In future, people will 

simply talk about “casting alloys”. In 

practice, this is already the case. Metal 

from used parts is converted back into 

the same fi eld of application. The DIN 

EN 1676 and 1706 standards with their 

rather fl uid quality transitions take this 

trend into account. 

Aleris is one of only a few companies 

to produce a wide range of aluminium 

alloys; our product spectrum extends 

from classic secondary alloys to highpurity 

alloys for special applications. 

Production is in full compliance with 

the European DIN EN 1676 standard 

or international standards and in many 

cases, manufactured to specifi c cus- 

tomer requirements. We have also been 

offering several aluminium casting al- 

loys as protected brand-name alloys 

for many years, e.g. Silumin ®® , Pantal ®® 

and Autodur ® . 

Our casting alloys are delivered in the 

form of ingots with a unit weight of approx. 

6 kg or as liquid metal. 

We distinguish between ingots cast in 

open moulds and horizontal continu- 

ously cast ingots (so-called HGM). Ingots 

are dispatched in bundles of up to 

approx. 1,300 kg. 

The delivery of liquid or molten metal is 

useful and economic when large quanti- 

ties of one homogeneous casting alloy are 

required and the equipment for tapping 

and holding the molten metal containers 

is available. Supplying molten metal can 

lead to a substantial reduction in costs 

as a result of saving melting costs and 

a reduction in melting losses. The supply 

of liquid metal also provides a viable 

alternative in cases where new melting 

capacities need to be built to comply 

with emission standards or where space 

is a problem. 

Aluminium Casting Alloys 11

Technical consultancy service 

The technical consultancy service is 

the address for questions relating to 

foundry technology. We provide assis- 

tance in clarifying aluminium casting alloy 

designations as stated in German and 

international standards or the temper 

conditions for castings. We also offer 

advice on the selection of alloys and can 

provide aluminium foundries or users of 

castings with information on: 

Aluminium casting alloys 

Chemical and physical properties 

Casting and solidifi cation 

behaviour 

Casting processes and details 

regarding foundry technology 

Melt treatment possibilities, such as 

cleaning, degassing, modifi cation 

or grain refi nement 

Possibilities of infl uencing the 

strength of castings by means 

of alloying elements or heat 

treatment 

Questions relating to surface 

fi nish and surface protection. 

12 


Technical consultants also provide as- 

sistance in evaluating casting defects or 

surface fl aws and offer suggestions with 

regard to eliminating defects. They sup- 

ply advice on the design of castings, the 

construction of dies, the casting system 

and the confi guration of feeders. 

Technical consultants also provide tech- 

nical support to aluminium foundries in 

the preparation of chemical analyses, 

microsections and structural analyses. 

Customer feedback coupled with exten- 

sive experience in the foundry sector fa- 

cilitates the continuous optimisation and 

quality improvement of our aluminium 


In co-operation with our customers, we 

are working on gaining wider acceptance 

of our aluminium casting alloys in new 

fi elds of application. 

Where required and especially where 

fundamental problems arise, we arrange 

contracts with leading research institutes 

in Europe and North America.

Selecting aluminium casting alloys 

To supplement and provide greater depth 

to our technical explanations, we refer 

you to standard works on aluminium 

and aluminium casting alloys. Further 

details on other specialist literature are 

available and can be requested at any 

time. We would be delighted to advise 

you in such matters. 

Should you have any queries or com- 

ments, which are always welcome, 

please contact our technical service. 

Standard works on aluminium and aluminium 

casting alloys: 

“Aluminium-Taschenbuch”, Verlag 

Beuth, Düsseldorf 

“Aluminium viewed from within - 

Profi le of a modern metal”, Prof. 

Dr. D. G. Altenpohl, Verlag Beuth, 

Düsseldorf. 

Once the requirements of a casting 

have been determined, the selection of 

the correct casting alloy from the multitude 

of possibilities often represents 

a problem for the designer and also for 

the foundryman. In this case, the “Aluminium-Taschenbuch” 

can be of great 

assistance. 

In the European DIN EN 1676 and DIN 

EN 1706 standards, the most important 

aluminium casting alloys have been collated 

in a version which is valid Europewide. 

Consequently, there are already 

more than 41 standard aluminium casting 

alloys available. 

Aluminium foundries should – according 

to their respective structure – limit themselves 

to as small a number of casting 

alloys as possible in order to use their 

melting equipment economically, to keep 

inventories as low as possible and to reduce 

the risk of mixing alloys. 

With regard to the quality of a casting, 

it is more sensible to process a casting 

alloy which is operational in use than one 

which displays slightly better properties 

on paper but is actually more diffi cult to 

process. The quality potential of a casting 

alloy is only exploited in a casting if 

the cast piece is as free as possible of 

casting defects and is suitable for subsequent 

process steps (e.g. heat treatment). 

Our sales team and technicians are on 

hand to provide foundries and users 

of castings with assistance in selecting 

the correct aluminium casting alloy. 

As far as possible, the use of common 

aluminium casting alloys is recommended. 

These involve well-known and proven 

casting alloys and we stand fully behind 

the quality properties of these casting 

alloys which are often manufactured in 

large quantities, are more cost-effective 

than special alloys and, in most cases, 

can be delivered at short notice. 


Criteria for the selection of 

aluminium casting alloys 

In the following section, we provide an 

insight into the chemical and physical 

potentials of aluminium casting alloys by 

describing their various properties. The 

standardisation provided here helps to 

establish whether a casting alloy is suitable 

for the specifi c demands placed 

on a casting. 

Degree of purity 

One important selection criteria is the de- 

gree of purity of a casting alloy. With the 

increasing purity of a casting alloy family, 

the corrosion resistance and ductility of 

the as-cast structure also increase; the 

selection of pure feedstock for making 

casting alloys, however, will necessarily 

cause costs to rise. 

The increasing importance of the closedcircuit 

economy means that, for the producer 

of aluminium casting alloys, the 

transition between the previous quality 

grades for aluminium casting alloys is 

becoming ever more fl uid. 

Due to their high purity, casting alloys 

made from primary aluminium display the 

best corrosion resistance as well as high 

ductility. By way of example, Silumin-Beta 

with max. 0.15 % Fe, max. 0.03 % Cu 

and max. 0.07 % Zn can be mentioned. 

In many countries, the Silumin trademark 

has already become a synonym for aluminium-silicon 


14 


Classifi cation of casting alloys acc. to strength properties 1) 

Table 1 

Casting alloy Temper Tensile Elongation Brinell 

strength hardness 

Rm [MPa] 

A5 [%] HB 

Strong Al Cu4Ti T6 330 7 95 

and ductile Silumin-Beta T6 290 4 90 

Al Si10Mg(a) T6 260 1 90 

Hard Al Si8Cu3 F 170 1 75 

Al Si18CuNiMg F 180 1 90 

Ductile Silumin F 170 7 45 

Other Al Mg3 F 150 5 50 

1) Typical values for permanent mould casting, 

established on separately-cast test bars. 

Casting alloys made from scrap are, 

with regard to ductility and corrosion 

resistance, inferior to other casting alloy 

groups due to their lower purity. They are, 

however, widely applicable and meet the 

set performance requirements. 

Strength properties 

Strength properties should be discussed 

as a further selection criterion (Table 1). 

A rough subdivision into four groups is 

practical: 

“strong and ductile” 

The most important age-hardenable 

casting alloys belong to this group. By 

means of different kinds of heat treatment, 

their properties can be adjusted 

either in favour of high tensile strength 

or high elongation. In Table 1, the typical 

combinations of R and A values for 

m 

different casting alloys are compared. 

These casting alloys are used for highgrade 

construction components, especially 

for critical parts. 

“hard” 

The casting alloys of this group must 

display a certain tensile strength and 

hardness without particular requirements 

being placed on the metal‘s elongation. 

First of all, Al SiCu alloys belong to this 

group. Due to their Cu, Mg and Zn content, 

these casting alloys experience a 

certain amount of self-hardening after 

casting (approx. 1 week). These alloys 

are particularly important for pressure 

die casting since it is in pressure die 

casting – except for special processes 

such as vacuum die casting – that process-induced 

structural defects occur, 

preventing high elongation values. Due 

to its particularly strong self-hardening 

characteristics, the Autodur casting al-

Table 2 

Classifi cation of casting alloys acc. to casting properties 

Fluidity Thermal 

crack 

susceptibility 

Casting alloy Type of solidifi cation 

High Low Silumin 

Al Si12 

Exogenous-shell forming 

Al S12(Cu) Exogenous-rough wall 

Al Si10Mg 

Silumin-Beta 

Al Si8Cu3 

Pantal 7 

Al Si5Mg 

Al Cu4Ti 

Endogenous-dendritic 

Al Mg3 Endogenous-globular 

Low High Al Mg5 Mushy 

loy represents a special case allowing 

hardness values of approx. 100 HB and 

a corresponding strength – albeit at very 

low ductility – in all casting processes. 

Hypereutectic AlSi casting alloys such 

as Al Si18CuNiMg and Al Si17Cu4Mg, 

for example, which display particularly 

high wear resistance due to their high 

silicon content, can also be classifi ed 

in this group. 

“ductile” 

Casting alloys which display particu- 

larly high ductility, e.g. Silumin-Kappa 

(Al Si11Mg), come under this general 

heading. This casting alloy is frequently 

used for the manufacture of automobile 

wheels. 

In this particular application, a high elongation 

value is required for safety reasons. 

“other” 

Casting alloys for more decorative purposes 

with lower strength properties, e.g. 

Al Mg3, belong to this category. 

Casting properties 

Further selection criteria comprise cast- 

ing properties such as the fl uidity or 

solidifi cation behaviour which sets the 

foundryman certain limits. Not every 

ideally-shaped casting can be cast in 

every casting alloy. 

A simplifi ed summary of the casting prop- 

erties associated with the most important 

casting alloys is shown in Table 2. 

Co-operation between the technical designer 

and an experienced foundryman 

works to great advantage when looking 

for the optimum casting alloy for a particular 

application. 

Given constant conditions, the fl uidity 

of a metallic melt is established by de- 

termining the fl ow length of a test piece. 

Theoretically, low fl uidity can be offset 

by a higher casting temperature; this is, 

however, linked with disadvantages such 

as oxidation and hydrogen absorption as 

well as increased mould wear. Eutectic 

AlSi casting alloys such as Silumin or 

Al Si12 display high fl uidity. Hypoeutectic 

AlSi casting alloys such as Pantal 7 have 

medium values. AlCu and AlMg casting 

alloys display low fl uidity. 

Hypereutectic AlSi casting alloys such 

as Al Si17Cu4Mg occupy a special posi- 

tion. In their case, very long fl ow paths 

are observed. This does not however 

necessarily lead to a drop in the melt 

temperature since primary silicon crystals 

already form in the melt. The melt 

still fl ows well because the latent heat 

of solidifi cation of the primary silicon 


Selection criteria for aluminium casting alloys 

Casting properties Strength characteristics Corrosion 

resistance* 

Shrinkage Fluidity Thermal crack High strength Strong Ductile Hard 

formation susceptibility and ductile (T6) and ductile 

Coarse High Low Silumin 

Silumin-Kappa 

Silumin-Delta 

Al Si12 

Silumin-Beta 

Pantal 7 

Al Cu4Ti 

Al Si12(Cu) 

Al Si10Mg 

Al Si10Mg(Cu) 

Al Mg3Si 

Al Si12CuNiMg 

Al Si17Cu4Mg 

Al Si18CuNiMg 

Autodur 

Al Si8Cu3 

Al Mg3 

Al Mg5 

Fine Low High Al Mg9 

* Analogue to DIN EN 1706 

heats up the remainder of the melt. The 

already solidifi ed silicon, however, causes 

increased mould wear and very uneven 

distribution in the castings. In these 

casting alloys, high melting and holding 

temperatures are necessary so that a 

casting temperature of at least 720 °C 

for pressure die casting and 740 °C 

for sand and gravity die casting has to 

be attained. 

The susceptibility to hot tearing is almost 

the opposite of fl uidity (Tables 2 and 3). 

By hot tearing, we mean a separation of 

the already crystallised phases during 

16 


solidifi cation, e.g. under the infl uence of 

shrinkage or other tensions which can 

be transmitted via the casting moulds. 

The cracks or tears arising can be healed 

by, among other things, the feeding of 

residual melt. Eutectic and near-eutectic 

AlSi casting alloys also behave particularly 

well in this case, while AlCu and AlMg 

casting alloys behave particularly badly. 

In practice, there are mixed forms and 

transitional forms of these solidifi cation 

modes. The solidifi cation behaviour is 

responsible for the formation of shrink- 

Table 3 

age cavities and porosity, for example, 

or other defects in the cast structure 

as it determines the distribution of the 

volume defi cit in the casting. To curb 

the aforementioned casting defects, 

casting/technical measures need to be 

taken: e.g. by making adjustments to 

the sprue system, the thermal balance 

of the mould or by controlling the gas 

content of the melt. A volume defi cit 

occurs during transition from liquid to 

solid state. This is quite small in high 

silicon casting alloys since the silicon 

increases in volume during solidifi cation. 

In any case, the volume defi cit incurred

needs to be offset as far as possible by 

casting/technical means (see also the 

section on “Avoiding casting defects”). 

Figure 1 indicates the main types of so- 

lidifi cation; each type is shown at two 

successive points in time. With regard 

to aluminium, only high-purity aluminium 

belongs to Solidifi cation Type A (“exogenous-shell 

forming”). The only casting 

alloy which corresponds to this type is 

the eutectic silicon alloy or Al Si12 with 

approx. 13 % silicon. 

The hypoeutectic AlSi casting alloys 

solidify according to Type C (“spongy”), 

AlMg casting alloys according to a mix- 

ture of Types D and E (“mushy” or “shellforming”). 

The remaining casting alloys 

also represent intermediate types. At high 

solidifi cation speeds, the solidifi cation 

types move upwards, i.e. in the direction 

of “exogenous-rough wall”. 

Shell-forming casting alloys with “smooth- 

wall” or “rough-wall” solidifi cation are sus- 

ceptible to the formation of macroshrink- 

age which can only be prevented to a 

limited extent by feeding. Casting alloys 

of a spongy-mushy type are susceptible 

to shrinkage porosity which can only be 

avoided to a limited extent by feeding. 

In castings which demand feeding by 

material accumulation in particular and 

Exogenous solidifi cation types 

A Smooth wall B Rough wall C Spongy 

Endogenous solidifi cation types 

D Mushy E Shell forming 

Mould 

Fluid 

Strong 

Picture 1 

which should be extensively pore-free – 

as well as pressure-tight – the preferred 

casting alloys are to be found at the top 

of Table 3. 

For complex castings whose geometry 

does not allow each material accumulation 

to be achieved with a feeder, the 

casting alloys listed in Table 3 offer advantages 

provided that a certain amount 

of microporosity is taken into account. 


i Fe 

Infl uence of the most important 

alloying elements on aluminium 


Silicon 

improves the casting properties 

produces age-hardenability in 

combination with magnesium but 

causes a grey colour during anodisation 

in pure AlCu casting alloys (e.g. 

Al Cu4Ti), silicon is a harmful impurity 

and leads to hot tearing 

susceptibility. 

Iron 

at a content of approx. 0.2 % and 

above, has a decidedly negative 

infl uence on the ductility (elongation 

at fracture); this results in a 

very brittle AlFe(Si) compound in 

the form of plates which appear in 

micrographs as “needles”; these 

plates act like large-scale microstructural 

separations and lead to 

fracture when the slightest strain 

is applied 

at a content of approx. 0.4 % and 

above, reduces the tendency to 

stickiness in pressure die casting. 

18 


Copper 

increases the strength, also at 

high temperatures (hightemperature 

strength) 

produces age-hardenability 

impairs corrosion resistance 

in binary AlCu casting alloys, the 

large solidifi cation range needs to 

be taken into account from a 

casting/technical point of view. 

Manganese 

partially offsets iron‘s negative 

effect on ductility when iron 

content is > 0.15 % 

segregates in combination with 

iron and chromium 

reduces the tendency to stickiness 

in pressure die casting. 

Magnesium 

produces age-hardenability in 

combination with silicon, 

copper or zinc; with zinc also 

self-hardening 

improves corrosion resistance 

increases the tendency towards 

oxidation and hydrogen 

absorption 

binary AlMg casting alloys are 

diffi cult to cast owing to their large 

solidifi cation range. 

Zinc 

increases strength 

produces (self) age-hardenability 

in conjunction with magnesium. 

Nickel 

increases high-temperature 

strength. 

Titanium 

increases strength (solid-solution 

hardening) 

produces grain refi nement on its 

own and together with boron.

Infl uencing the microstructural 

formation of aluminium castings 

Measures infl uencing microstructural 

formation are aimed at improving the 

mechanical and casting properties. In 

practice, apart from varying the cooling 

speed by means of different mould 

materials, additions to the melt are usually 

used. 

Common treatment measures include: 

grain refi nement of the solid 

solution with Ti and/or B 

transformation of the eutectic Si 

from lamellar into granular form 

modifi cation of the eutectic Si 

with Na or Sr 

refi nement of the eutectic 

Si with Sb 

refi nement of the Si primary 

phase with P or Sb. 

The marked areas in Figure 1 denote 

where it makes sense to carry out the 

respective types of treatment on AlSi 


Some of these measures are explained 

in more detail in the following section. 

Types of treatment to infl uence grain structure Figure 1 

Temperature 

[°C] 

700 

600 

500 

400 

0 2 4 6 8 10 12 14 16 18 20 22 24 

Silicon [wt. – %] 

Primary Si refi nement 

Grain refi nement 

Modifi cation 

Melt 

+ Al 660 °C 

Al Al + Si 

Melt 

Melt + Si 

Eutectic temperature 577 C° 

Al Si5 Al Si7 Al Si9 Al Si12 Al Si18 


Grain refi nement 

The solidifi cation of many aluminium 

casting alloys begins with the formation 

of aluminium-rich dendritic or equiaxed 

crystals. In the beginning, these solidifi ed 

crystallites are surrounded by the remain- 

ing melt and, starting from nucleation 

sites, grow on all sides until they touch 

the neighbouring grain or the mould wall. 

The characterisation of a grain is the 

equiaxed spatial arrangement on the 

lattice level. For casting/technical or 

optical/decorative reasons as well as 

for reasons of chemical resistance, it is 

often desirable to set the size of these 

grains as uniformly as possible or as fi nely 

as technically possible. To achieve this, 

so-called grain refi nement is frequently 

carried out. The idea is to offer the solidifying 

aluminium as many nucleating 

agents as possible. 

Since grain refi nement only affects the 

α-solid solution, it is more effective when 

the casting alloy contains little silicon, 

i.e. a lower fraction of eutectic (Figure 2). 

Grain refi nement is particularly important 

in AlMg and AlCu casting alloys in order 

to reduce their tendency to hot tearing. 

From a technical and smelting perspective, 

grain refi nement mostly takes place 

by adding special Al TiB master alloys. 

20 


We pre-treat the appropriate casting alloys 

when producing the alloys so that 

grain refi nement in the foundry is either 

unnecessary or only needs a freshen- 

up. The latter can be done in the form of 

salts, pellets or preferably with titanium 

master alloy wire, following the manufacturer’s 

instructions. 

Effect of silicon content on grain 

refi nement with Al Ti5B1 master alloy 

Mean grain diameter Casting temperature 720 °C 

[µm] 

1400 

holding time 5 min 

1200 

1000 

800 

600 

400 

200 

0 

Columnar and 

equiaxed crystals 

Silicon [%] 

Without grain 

refi nement 

With grain refi nement 

Al Ti5B1: 2,0 kg/mt 

Since every alloying operation means 

more contaminants in the melt, grain 

refi nement should only be carried out 

for the reasons referred to above. 

Figure 2 

0 2 4 6 8 10 12 

To make a qualitative assessment of a 

particular grain refi nement treatment, 

thermal analysis can be carried out (see 

section on “Melt testing and inspection 

procedure”).

Modifi cation of AlSi eutectic 

(refi nement) 

By “modifi cation”, we mean the use 

of a specifi c melt treatment to set a 

fi ne-grained eutectic silicon in the cast 

structure which improves the mechanical 

properties (and elongation in particular) 

as well as the casting properties in many 

cases. As a general rule, modifi cation 

is carried out by adding small amounts 

of sodium or strontium. To facilitate an 

understanding of the possible forms of 

eutectic silicon, these are depicted in 

Figure 2 (a-e) for Al Si11 with a varying 

Na content: 

a) The lamellar condition only 

appears in casting alloys which 

are virtually free of phosphorous 

or modifi cation agents, e.g. 

Na or Sr. 

b) In granular condition which 

appears in the presence of 

phosphorous without Na or Sr, the 

silicon crystals exist in the form of 

coarse grains or plates. 

c) In undermodifi ed and 

d) to a great extent in fully-modifi ed 

microstructural condition, e.g. 

by adding Na or Sr, they are 

signifi cantly reduced in size, 

rounded and evenly distributed 

which has a particularly positive 

effect on elongation. 

e) In the case of overmodifi cation 

with sodium, vein-like bands with 

coarse Si crystals appear. 

Overmodifi cation can therefore 

mean deterioration as regards 

mechanical properties. 

Figures 3 and 4 depict the formation of 

microstructural conditions or the degree 

of modifi cation as a result of interaction 

between sodium and strontium and the 

phosphorous element. It can be ascer- 

tained that the disruption of modifi cation 

due to small amounts of phosphorous 

is relatively slight. In Sr modifi cation, a 

high phosphorous content can be offset 

by an increased amount of modifying 

agent. In aluminium casting alloys with a 

silicon content exceeding 7 %, eutectic, 

silicon takes up a larger part of the area 

of a metallographic specimen. From a 

silicon content of approx. 7 to 13 %, 

the type of eutectic formation, e.g. 

grained or modifi ed, thus plays a key 

role in determining the performance 

characteristics, especially the ductility 

Types of grain structure 

a) Lamellar b) Granular 

d) Modifi ed 

e) Overmodifi ed 

or elongation. When higher elongation is 

required in a workpiece, aluminium cast- 

ing alloys containing approx. 7 to 13 % 

silicon will thus be modifi ed by adding 

approx. 0.0040 to 0.0100 % sodium (40 

to 100 ppm). 

In casting alloys with approx. 11 % silicon, 

particularly for use in low-pressure die 

casting, strontium can also be used as a 

long-term modifi er since the melting loss 

behaviour of this element is substantially 

better than that of sodium. In this case, 

the recommended addition is approx. 

0.014 to 0.04 % Sr (140 to 400 ppm). 

With suitable casting alloys, the required 

amount of strontium can be added 

during alloy manufacture so that, as 

a rule, the modifi cation process step 

c) Undermodifi ed 

Picture 2 


Microstructural formation in relation to 

the content of phosphorous and sodium Al Si7Mg 

Sodium Sand casting 

[ppm] 

140 

cooling rate 0.1 K/s 

120 

100 

80 

60 

40 

20 

0 

Overmodifi ed 

Granular 

Modifi ed 

Lamellar 

can be omitted in the foundry. At low 

cooling rates, strontium modifi cation is 

less effective so that it is not advisable 

to use this in sand casting processes. 

To avoid the burn-off of strontium, any 

cleaning and degassing of Sr-modifi ed 

melts should be carried out with chlorine- 

free preparations only, preferably using 

argon or nitrogen. Strontium modifi cation 

is not greatly impaired even when 

remelting revert material. Larger losses 

22 


Phosphorous [ppm] 

Undermodifi ed 

Figure 3 

0 5 10 15 20 25 30 35 40 45 50 55 60 

can be offset by adding Sr master alloy 

wire in accordance with the respective 

manufacturer‘s instructions. At the right 

temperature, the addition of sodium to 

the melt is best done by charging standard 

portions. For easy handling, storage 

and proportioning, the manufacturer‘s 

recommendations and safety instructions 

should be followed. 

Since sodium burns off from the melt 

relatively quickly, subsequent modifi - 

Figure 4 

Microstructural formation in relation to 

the content of phosphorous and strontium Al Si7Mg 

Strontium Gravity die casting 

[ppm] gravity die cast test bar 

cooling rate 2.5 K/s 

450 

400 

350 

300 

250 

200 

150 

100 

50 

0 

0 10 20 30 40 50 60 70 80 90 100 


Modifi ed Undermodifi ed Granular Lamellar 

cation must take place in the foundry 

at regular intervals. In melts modifi ed 

with sodium, any requested cleaning 

and degassing should be carried out 

with chlorine-free compounds only 

(argon or nitrogen). A certain amount 

of sodium burn-off is to be reckoned 

with, however, and needs to be taken 

into account in the subsequent addition 

of sodium. When absolutely necessary, 

the melt can be treated with chlorine- 

releasing compounds long before the

fi rst addition of sodium. If such treat- 

ment is carried out after adding sodium 

or strontium, chlorine may react with 

these elements and remove them from 

the melt, thereby preventing any further 

modifi cation. 

Modifi cation with sodium or strontium 

increases the tendency to gas absorption 

in the melt. As a result of the reaction 

of the precipitating hydrogen with 

the rapidly-forming oxides, defects can 

occur in the casting, especially cumulant 

microporosity. In many practical cases, 

this potential for micropore formation 

is even desirable. Then, the purpose 

of modification is also to offset the 

expected macroshrinkage by forming 

many micropores. 

An accurate assessment of the effects 

of modifi cation can only be made by 

means of metallographic examination. 

As a quick test, thermal analysis can be 

carried out if it is possible to establish by 

means of a preliminary metallographic 

examination which depression value is 

necessary to attain a suffi ciently-modi- 

fi ed grain structure (for more information 

on thermal analysis, please refer to the 

section on “Methods for monitoring the 

melt”). Under the same conditions, rapid 

determination of the modifi ed condition 

is also possible by measuring the electrical 

conductance of a sample. 

In aluminium casting alloys of the type 

Al Si7Mg, a refi nement of the eutectic 

silicon with antimony (Sb) is possible. 

A Sb content of at least 0.1 % is required. 

This treatment, however, only produces 

a fi ner formation of the lamellar eutectic 

silicon and is not really modifi cation 

in the traditional sense. The danger of 

contamination of other melts by closedcircuit 

material containing Sb exists as 

even a Sb content of approx. 100 ppm 

can disturb normal sodium or strontium 

modifi cation. What‘s more, refi nement 

with antimony can be easily disturbed 

by only a low level of phosphorous (a 

few ppm) (Figure 5). In contrast to modifi 

cation, refi nement with antimony can 

not be checked by means of thermal 

analysis of a melt sample. 

Figure 5 

Infl uence of antimony and phosphorous 

content on the form of the eutectic silicon of Al Si7Mg 

Antimony 

[%] 

0.30 

0.20 

0.10 

0.00 

Coarse-lamellar 

Acceptable Coarse-lamellar 

to granular 


Refi nement of primary silicon 

In hypereutectic AlSi casting alloys 

(e.g. Al Si18CuNiMg), the silicon-rich, 

polygonal primary crystals solidify fi rst. 

To produce as many fi ne crystals as pos- 

sible in the as-cast structure, nucleating 

agents need to be provided. 

High-purity base 

0 2 4 6 8 10 

This is done with the aid of prepara- 

tions or master alloys which contain 

phosphorous-aluminium compounds. 

This treatment can also be carried out 

when the alloy is being manufactured 

and, in most cases, the foundryman 

does not need to repeat the process. 

If required, the quality of such primary 

refi nement can be checked by means 

of thermal analysis. 


Melt quality and melt cleaning 

All factors which come under the general 

term of “melt quality” have a direct 

effect on the quality of the casting to be 

produced. Inversely, according to DIN EN 

1706, the cast samples play a valuable 

role in checking the quality of the melt. 

Most problems in casting are caused by 

two natural properties of liquid melts, i.e. 

their marked tendency to form oxides 

and their tendency towards hydrogen 

absorption. Furthermore, other insoluble 

impurities, such as Al-carbides or 

refractory particles as well as impurities 

with iron, play an important role. 

As mentioned in other sections, the 

larger oxide fi lm can lead to a material 

separation in the microstructure and, 

consequently, to a reduction in the load- 

bearing cross-section of the casting. 

The solubility of hydrogen in aluminium 

decreases discontinuously during the 

transition from liquid to solid so that as 

solidifi cation takes place, precipitating 

gaseous hydrogen reacting with existing 

oxides can cause voids which can 

in turn take various forms ranging from 

large pipe-like blisters to fi nely-distributed 

micro-porosity. 

24 


Critical melting temperatures 

in relation to the segregation factor 

Temperature 

[°C] 

650 

640 

630 

620 

610 

600 

590 

0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 

Segregation factor [(Fe)+2(Mn)+3(Cr)] 

Al Si8Cu3 Al Si6Cu4 Al Si12(Cu) 

To achieve good melt quality, the for- 

mation of oxides and the absorption 

of hydrogen have to be suppressed as 

much as possible on the one hand, while 

other hydrogen and oxides have to be 

removed from the melt as far as possible 

on the other, although this is only 

possible to a certain extent. 

Figure 6

Avoiding impurities 

Ingot quality 

An essential prerequisite for a good 

casting is good ingot quality. The metal 

should be cleaned effectively and the in- 

gots should display neither metallic nor 

non-metallic inclusions. The ingots must 

be dry (there is a risk of explosion when 

damp) and no oil or paint residue should 

be present on their surface. When using 

revert material, this should be in lumps, 

if possible, and well cleaned. 

Melting 

When melting ingots or revert material, 

it must be ensured that the metal is not 

exposed unnecessarily to the fl ame or 

furnace atmosphere. The pieces of metal 

should be melted down swiftly, i.e. follow- 

ing short preheating, immersed directly 

in the liquid melt. 

Large-volume hearth or crucible furnaces 

are best suited to melting. Furnaces with 

melting bridges are oxide producers and 

they lead to expensive, unnecessary and 

irretrievable metal losses. 

The type and state of the melt in contact 

with refractory materials are of particular 

importance in the melting and holding 

of aluminium. 

Aluminium and aluminium casting alloys 

in a molten state are very aggressive, especially 

when AlSi melts contain sodium 

or strontium as modifying agents. With 

an eye to quality, reactions, adherences, 

infi ltrations, abrasive wear and decompo- 

sition have to be kept within limits when 

using melting crucibles and refractory 

materials as well as during subsequent 

processing. The care and maintenance 

as well as cleanliness of equipment are 

equally important. Adhering materials 

can very easily lead to the undesired 

redissolving of oxides in the melt and 

cause casting defects. 

Melting temperature 

The temperature of the melt must be set 

individually for each alloy. 

Too low melting temperatures lead to 

longer residence times and, as a result, 

to greater oxidation of the pieces jut- 

ting out of the melt. The melt becomes 

homogeneous too slowly, i.e. local undercooling 

allows segregation to take 

place, even as far as tenacious gravity 

segregation of the FeMnCrSi type phases. 

The mathematical interrelationship for 

the segregation of heavy intermetallic 

phases is depicted in Figure 6. 

Furthermore, at too low temperatures, 

autopurifi cation of the melt (oxides rising) 

can not take place. 

When the temperature of the melt is too 

high, increased oxide formation and 

gassing can occur. Lighter alloying elements, 

e.g. magnesium, are subject to 

burn-off in any case; this must be offset 

by appropriate additions. Too high 

melting temperatures aggravate this loss 

by burning. 


Conducting the melting operation 

As long as the melt is in a liquid condi- 

tion, it has a tendency to oxidise and 

absorb hydrogen. Critical points during 

subsequent processing include decanta- 

tion, the condition or maintenance of the 

transfer vessel, possible reactions with 

refractory materials as well as transport 

or metal tapping. The addition of grain 

refi ners and modifying agents above the 

required amount can lead to an increase 

in non-metallic impurities and greater 

hydrogen absorption. 

To minimise an enrichment of iron in the 

melt, direct contact between ferrous 

materials and the melt is to be avoided. 

For this reason, steel tools and containers 

(casting ladles) must be carefully 

dressed. Similarly, but also on economic 

grounds, the feed tubes for low-pressure 

die casting – made from cast iron up to 

now – should be replaced by ceramic 

feed tubes. 

Even during the casting process itself 

and especially due to turbulence in the 

fl ow channel, oxide skins can once again 

form which in turn can lead to casting 

defects. Casting technology is thus required 

to fi nd ways of preventing the 

excessive oxidation of the melt, e.g. by 

means of intelligent runners and gating 

systems (please refer to the section on 

“Selecting the casting process”). 

26 


Figure 7 

Hydrogen content of various 

casting alloy melts after different types of treatment 

Hydrogen 

[ml/100g] 

0.50 

0.40 

0.30 

0.20 

0.10 

0.00 

After melting 

10 20 30 0.5 2 4 24 10 20 

Rotary 

degassing 

[min] 

Holding 

in [h] 

Type of melt treatment 

Al Si8Cu3 Pantal 7 Al Mg5 

Gassing 

Rotary 

degassing 

[min] 

24h

Cleaning and degassing the melt 

Our casting alloys consist of effectively 

cleaned metal. Since reoxidation always 

takes place during smelting, and in 

practice revert material is always used, 

a thorough cleaning of the melt is necessary 

prior to casting. 

Holding the aluminium melt at the cor- 

rect temperature for a long time is an ef- 

fective cleaning method. It is, however, 

very time-intensive and not carried out 

that often as a result. Foundrymen are 

thus left with only intensive methods, i.e. 

using technical equipment or the usual 

commercially available mixture of salts. 

In principle, melt cleaning is a physical 

process: the gas bubbles rising through 

the liquid metal attach oxide fi lms to their 

outer surfaces and allow hydrogen to dif- 

fuse into the bubbles from the melt. Both 

are transported to the bath surface by the 

bubbles. It is therefore clear that in order 

for cleaning of the melt to be effective, it 

is desirable to have as many small gas 

bubbles as possible distributed across 

the entire cross-section of the bath. 

Dross can be removed from the surface 

of the bath, possibly with the aid of oxide-binding 

salts. 

Inert-gas fl ushing by means of an im- 

peller is a widely-used, economical and 

environmentally-sound cleaning process. 

The gas stream is dispersed in the form 

of very small bubbles by the rapid turning 

of a rotor and, in conjunction with the 

good intermixing of the melt, this leads 

to very effi cient degassing. To achieve 

an optimum degassing effect, the various 

parameters such as rotor diameter 

and revolutions per minute, gas fl ow 

rate, treatment time, geometry and size 

of the crucible used as well as the alloy, 

have to be co-ordinated. The course of 

degassing and reabsorption of hydrogen 

is depicted for various casting alloys 

in Figure 7. 

When using commercially available salt 

preparations, the manufacturer‘s instruc- 

tions concerning use, proportioning, 

storage and safety should be followed. 

Apart from this, attention should also be 

paid to the quality and care of tools and 

auxiliary materials used for cleaning so 

that the cleaning effect is not impaired. 

If practically feasible, it is also possible 

to fi lter the melt using a ceramic foam 

fi lter. In the precision casting of high- 

grade castings, especially in the sand 

casting process, the use of ceramic 

fi lters in the runner to the sand mould 

has proved to be a success. Above all, 

such a fi lter leads to an even fl ow and 

can retain coarse impurities and oxides. 

In the gravity die casting of sensitive 

hydraulic parts, or when casting sub- 

sequently anodised decorative fi ttings 

in Al Mg3, ladling out of a device which 

is fi tted with in-line fi lter elements and 

separated from the remaining melt bath 

is very common. 


Melt testing and inspection procedure 

To assess the effectiveness of the clean- 

ing process or the quality of the melt, the 

following test and inspection methods 

can be used to monitor the melt: 

Reduced pressure test 

This method serves to determine the 

tendency to pore formation in the melt 

during solidifi cation. A sample, which 

can contain a varying number of gas 

bubbles depending on the gas content, 

is allowed to solidify at an underpressure 

of 80 mbar. The apparent density is then 

compared with that of a sample which 

is solidifi ed at atmospheric pressure. 

The so-called “Density Index” is then 

calculated using the following equation: 

DI = (dA - d80)/dA x 100 % 

DI = Density Index 

dA = density of the sample solidifi ed 

at atmospheric pressure 

d80 = density of the sample solidifi ed 

at under 80 mbar 

28 


The Density Index allows a certain inference 

to be drawn about the hydrogen 

content of the melt. It is, however, strongly 

infl uenced by the alloying elements and, 

above all, by varying content of impurities 

so that the hydrogen content must not 

on any account be stated as a Density 

Index value (Figure 8). 

The assessment of melt quality by means 

of an underpressure density sample therefore 

demands the specifi c determination 

of a critical Density Index value for each 

casting alloy and for each application. 

The underpressure density method is, 

however, a swift and inexpensive method 

with the result that it is already used 

in many foundries for quality control. 

To keep results comparable, sampling 

should always be carried out according 

to set parameters. 

Determination of the hydrogen 

content in the melt 

Reliable instruments have been in operation 

for years for measuring the hydrogen 

content in aluminium melts. They work 

according to the principle of establishing 

equilibration between the melt and a 

measuring probe so that the actual gas 

content in the melt is determined and not 

in the solid sample. In this way, the effectiveness 

of the degassing treatment can 

be assessed quickly. The procurement of 

such an instrument for continuous quality 

monitoring is only worthwhile when it is 

used frequently; in small foundries, the 

hiring of an instrument to solve problems 

is suffi cient.

Determination of insoluble 

non-metallic impurities 

For determining the number and type 

of insoluble non-metallic impurities in 

aluminium melts, the Porous Disc Filtration 

Apparatus (PoDFA) method, among 

others, can be used. In this particular 

method, a precise amount of the melt 

is squeezed through a fi ne fi lter and 

the trapped impurities are investigated 

metallographically with respect to their 

type and number. The PoDFA method 

is one of the determination procedures 

which facilitates the acquisition, both 

qualitatively and quantitatively, of the 

impurity content. It is used primarily for 

evaluating the fi ltration and other clean- 

ing treatments employed and, in casting 

alloys production, is utilised at regular 

intervals for the purpose of quality control. 

This method is not suitable for making 

constant routine checks since it is very 

time-consuming and entails high costs. 

Correlation between the hydrogen content 

and density index in unmodifi ed Al Si9Mg alloy 

Density index Measurement acc. to Chapel 

[%] 

35 

at vacum 30 mbar 

30 

25 

20 

15 

10 

5 

0 

0 0.1 0.2 0.3 0.4 0.5 0.6 

Hydrogen content [ml/100g] 

Figure 8 


Thermal analysis 

To evaluate the effectiveness of melt 

treatment measures, e.g. modifi cation, 

grain refi nement and primary silicon re- 

fi ning, thermal analysis has proved itself 

to be a fast and relatively inexpensive 

method in many foundries. The test 

method is based on the comparison of 

two cooling curves of the investigated 

melts (Figures 9 and 10). 

The undercooling effect (recalescence) 

occurring during primary solidifi cation 

allows conclusions to be made about 

the effectiveness of a grain refi nement 

treatment, whereby the recalescence 

values do not however allow conclusions 

to be drawn as regards the later grain 

size in the microstructure. Modifi cation is 

shown in thermal analysis by a decrease 

in the eutectic temperature (depression) 

in comparison to the unmodifi ed state. 

Here too, the level of the depression 

values depend strongly on the content 

of accompanying and alloying elements 

(e.g. Mg) and, consequently, the de- 

pression values required for suffi cient 

modifi cation must be established case 

by case, by means of parallel microstruc- 

tural investigations. 

30 


Thermal analysis for monitoring 

the grain refi nement of Al casting alloys 

Temperature 

[T] 

T L 

T L 

Time [t] 

With grain refi nement Without grain refi nement 

Liquidus temperature [T L ] 

Thermal analysis for monitoring 

the modifi cation of Al casting alloys 

Temperature 

[°C] 

585 

580 

577 

575 

570 

565 

560 

Figure 9 

0 10 20 

Time [sec] 

30 40 50 

Modifi ed Undermodifi ed Eutectic temperature 

Figure 10

Selecting the casting process 

As mentioned in the introduction, the 

entire “casting” process is the shortest 

route from molten metal to a part which 

is almost ready for use. All sections of 

this catalogue contain advice on how the 

entire experience should be carried out. 

The casting process is selected according 

to various criteria such as batch 

size, degree of complexity or requisite 

mechanical properties of the casting. 

Some examples: 

The sand casting process is used 

predominantly in two fi elds of appli- 

cation: for prototypes and small-scale 

production on the one hand and for the 

volume production of castings with a 

very complex geometry on the other. 

For the casting of prototypes, the main 

arguments in favour of the sand casting 

process are its high degree of fl exibility 

in the case of design changes and the 

comparably low cost of the model. In volume 

production, the level of complexity 

and precision achieved in the castings 

are its main advantages. 

When higher mechanical properties are 

required in the cast piece, such as higher 

elongation or strength, gravity die cast- 

ing, and to a limited extent pressure die 

casting, are used. In gravity die casting, 

there is the possibility of using sand 

cores. Large differences in wall thick- 

nesses can be favourably infl uenced 

with the help of risers. Cylinder heads 

for water-cooled engines represent a 

typical application. 

In the low-pressure gravity die process 

with its upward and controllable cavity 

fi lling, the formation of air pockets is re- 

duced to a minimum and, consequently, 

high casting quality can be achieved. In 

addition to uphill fi lling, the overpressure 

of approx. 0.5 bar has a positive effect 

on balancing out defects caused by 

shrinkage. The low-pressure die casting 

process is particularly advantageous in 

the casting of rotationally symmetrical 

parts, e.g. in the manufacture of passenger 

vehicle wheels. 

Pressure die casting is the most widely 

used casting process for aluminium 

casting alloys. Pressure die casting is 

of particular advantage in the volume 

production of parts where the requirement 

is on high surface quality and the 

least possible machining. Special applications 

(e.g. vacuum) during casting 

enable castings to be welded followed 

by heat treatment which fully exploits 

the property potential displayed by the 

casting alloy. 

In addition to conventional pressure die 

casting, thixocasting is worthy of mention 

since heat-treatable parts can also 

be manufactured using this process. 

The special properties are achieved 

by shaping the metal during the solidliquid 

phase. 

Squeeze-casting is another casting pro- 

cess to be mentioned; here, solidifi cation 

takes place at high pressure. In this way, 

an almost defect-free microstructure 

can be produced even where there are 

large transitions in the cross-section 

and insuffi cient feeding. 

Other special casting processes include: 

Precision casting 

Evaporative pattern casting 

Plaster mould casting 

Vacuum sand casting 

Centrifugal casting. 

The considerations above concern casting 

as an overall process. 

In the following notes on casting prac- 

tice, the actual pouring of the molten 

metal into prepared moulds and the 

subsequent solidifi cation control are 

looked at in more detail. 

From the numerous casting processes, 

which differ from one another in the type 

of mould material (sand casting, per- 

manent dies etc.) or by pressurisation 

(pressure die casting, low-pressure die 

casting etc.), a few notes are provided 

here on the most important processes. 


Pressure die casting process 

This process takes up the largest share. 

The hydraulically-controlled pressure 

die casting machine and the in-built 

die make up the central element of the 

process. The performance, the precise 

control of the hydraulic machine, the 

quality of the relatively expensive tools 

made from hot work steel are the decisive 

factors in this process. In contrast, 

the fl ow properties and solidifi cation 

of the aluminium casting alloys play a 

rather subordinate role in this “forced” 

casting process. 

The pouring operation in horizontal pressure 

die casting begins with the casting 

chamber being fi lled with metal. The 

fi rst movement, i.e. the slow advance of 

the plunger and the consequent pile-up 

of metal until the sleeve is completely 

fi lled, is the most important operation. 

In doing this, no fl ashover of the metal 

or other turbulence may occur until all of 

the air in the sleeve has been squeezed 

out. Immediately afterwards, the actual 

casting operation begins with the rapid 

casting phase. High injection pressure is 

essential to achieve high fl ow velocities 

in the metal. In this way, the die can be 

fi lled in a few hundredths of a second. 

Throughout the casting operation, the 

liquid metal streams are subject to the 

laws of hydrodynamics. Sharp turns 

and collisions with the die walls lead 

to a clear division of the metal stream. 

32 


Parts generated using the horizontal 

pressure die casting process are lightweight 

as low wall thicknesses can be 

achieved. They have a good surface 

fi nish, high dimensional accuracy and 

only require a low machining allowance 

in their design. Many bore holes can be 

pre-cast. 

The melting and casting temperatures 

should not be too low and should be 

checked constantly. Pre-melting alu- 

minium casting alloys is useful. The melt 

can thus be given a good clean in order 

to keep the melt homogeneous and to 

avoid undesirable gravity segregation 

(see Figure 6). From a statistical point 

of view, more casting defects arise from 

cold metal than from hot. It is particu- 

larly important to keep a suffi ciently high 

melting temperature, even with hypere- 

utectic alloys. These comments are also 

valid for other casting processes. 

Gravity die casting process 

The gravity die casting which includes 

the well-known low-pressure die casting 

process is applied. The main fi elds of 

application are medium- or high-volume 

production using high-grade alloys, and 

also low to medium component weight 

using heat-treatable alloys. Compared 

with sand casting, the aluminium castings 

display very good microstructural 

properties as well as good to very good 

mechanical properties which result from 

the rapid cooling times and the other 

easily-controlled operating parameters. 

The castings have high dimensional accuracy 

and stability as well as a good 

surface fi nish, are heat-treatable and 

can also be anodised. 

The basis for good quality castings is, 

not least, the right melt treatment and 

the appropriate casting temperature (see 

section on “Melt quality and melt cleaning”). 

For castings with high surface or 

microstructural quality requirements, 

such as in decorative or subsequently 

anodised components or in pressuretight 

hydraulic parts, it is useful to fi lter 

the melt before casting.

Demands on the casting system 

To keep disadvantages and defects – 

which constantly arise from an oxide 

skin forming on the melt – within limits, 

the gating system must guarantee low 

turbulence in the metal stream and also 

a smooth, controlled fi lling of the die 

cavity. With the transition from a liquid 

to a solid condition, volume contraction 

occurs; this can amount to up to 7 % 

of the volume. This shrinkage is controllable 

when the solid-liquid interface 

runs – controlled or directed – through 

the casting, mostly from the bottom to 

the top. This task, namely to effect a 

directed solidifi cation, can be achieved 

with a good pouring system. 

The castings are usually arranged “upright” 

in the die. The greatest mass can 

thus be placed in the bottom of the die. 

Quality requirements can be, for example, 

high strength, high-pressure tightness or 

decorative anodising quality. 

One example of an “ideal” gating system 

which meets the highest casting requirements 

is the so-called “slit gate system”. 

Here, the metal is conducted upwards 

continuously or discontinuously to the 

casting via a main runner. During mould 

fi lling, the melt is thus superimposed layer 

upon layer with the hotter metal always 

fl owing over the already solidifying metal. 

The standpipe ends in the top riser and 

supplies it with hot metal. This way, the 

solidifi cation can be directed from below, 

possibly supported by cooling, towards 

the top running through the casting and 

safeguarding the continuous supply of 

hot metal. When there is a wide fl are in 

the casting, the gating system has to be 

laid out on both sides. This symmetry en- 

sures a division of the metal and also an 

even distribution of the heat in the die. 

In low-pressure die casting, directing 

the solidifi cation by means of the gating 

system is not possible. Nor is there 

any great possibility of classic feeding. 

Directional solidifi cation is only possible 

by controlling the thermal balance of the 

die during casting. This mostly requires 

the installation of an expensive cooling- 

heating system. 

Simulation calculations for die fi lling and 

solidifi cation can be useful when laying 

out and designing the die and possibly 

the cooling. In actual production, the 

cooling and cycle time can be optimised 

by means of thermography (see section 

on “Solidifi cation simulation and ther- 

mography”). 


Sand casting process 

This process is used especially for in- 

dividual castings, prototypes and small 

batch production. It is, however, also 

used for the volume production of cast- 

ings with a very complex geometry (e.g. 

inlet manifolds, cylinder heads or crank- 

cases for passenger vehicle engines). 

During shaping and casting, most large 

sand castings display in-plane expan- 

sion. With this fl at casting method, gating 

systems like those which are normal in 

gravity die casting for directing solidifi ca- 

tion are often not applicable. If possible, 

a superimposed fi lling of the die cavity 

should be attempted here. 

34 


Another generally valid casting rule for 

correct solidifi cation is to arrange risers 

above the thick-walled parts, cooling (e.g. 

by means of chills) at opposite ends. This 

way, the risers can perform their main 

task longer, namely to conduct the supply 

of molten metal into the contracted 

end. Insulated dies are often helpful. 

The cross-section ratio in the sprue system 

should be something like the following: 

Sprue : 

Sum of the runner cross-section : 

Sum of the gates: 

like 1 : 4 : 4. 

This facilitates keeping the run-in laun- 

der full and leads to a smoother fl ow 

of the metal. This way, the formation of 

oxides due to turbulence can be kept 

within limits. The main runner must lie 

in the drag, the gates in the cope. In the 

production of high-grade castings, it is 

normal to install ceramic fi lters or sieves 

made from glass fi bre. The selection of 

the casting process and the layout of 

the casting system should be carried 

out in close co-operation between the 

customer, designer and foundryman (see 

section on “Casting-compliant design”).

Casting-compliant design 

The following notes on the design of 

aluminium castings are provided to help 

exploit in full the advantages and design 

possibilities of near net shape casting. 

They also align practical requirements 

with material suitability. 

Aluminium casting alloys can be processed 

in practically all conventional 

casting processes, whereby pressure die 

casting accounts for the largest volume, 

followed by gravity die casting and sand 

casting. The most useful casting process 

is not only dependent on the number and 

weight of pieces but also on other technical 

and economic conditions (see section 

on “Selecting the casting process”). 

To fi nd the optimum solution and produce 

a light part as cheaply and rationally as 

possible, co-operation between the designer, 

caster and materials engineer is 

always necessary. Knowledge concerning 

the loads applied, the distribution of 

stress, the range of chemical loading and 

operation temperatures is important. 

In the valid European standard, DIN EN 

1706 for aluminium castings, there are 

strength values only for separately-cast 

bars using sand and gravity die casting. 

For samples cut from the cast piece, 

a reduction in the 0.2 % proof stress 

and ultimate tensile strength values of 

up to 70 % and a decrease in elongation 

of up to 50 % from the test bar can 

be anticipated. When the alloy and the 

casting process are specifi ed, so too is 

the next point within the framework of 

the design, i.e. determination of the die 

parting line. Die parting on one level is 

not only the cheapest for patterns and 

dies but also for subsequent working and 

machining. Likewise, every effort should 

be made to produce a casting without 

undercuts. This is followed by designing 

and determining the actual dimensions 

of the part. The constant guideline must 

be to achieve a defect-free cast structure 

wherever possible. 

Only through good cast quality can the 

technical requirements be met and the 

full potential of the casting alloy be exploited. 

Every effort and consideration 

must be made therefore to design a light, 

functionally effi cient part whose manu- 

facture and machining can be carried out 

as effi ciently as possible. For this and 

subsequent considerations, the use of 

solidifi cation simulation is available (see 

section on “Solidifi cation simulation and 

thermography”). 

Casting alloys shrink during solidifi ca- 

tion, i.e. their volume is reduced. This 

increases the risk of defects in the cast 

structure, such as cavities, pores or 

shrinkage holes, tears or similar. The 

most important requirement is thus to 

avoid material accumulations by hav- 

ing as even a wall thickness as possible. 

In specialist literature, the following lower 

limits for wall thickness are given: 

Sand castings: 3-4 mm 

Gravity die castings: 2-3 mm 

Pressure die castings: 1-1.5 mm. 


The minimum values are also dependent 

on the casting alloy and the elongation of 

the casting. In pressure die casting, the 

minimum wall thickness also depends 

on the position of and distance to the 

gate system. 

Generally speaking, the wall thickness 

should be as thin as possible and only 

as thick as necessary. With increasing 

wall thickness, the specifi c strength of 

the cast structure deteriorates. 

Determining casting-compliant wall 

thicknesses also means, especially with 

sand and gravity die casting, that the die 

must fi rst of all be fi lled perfectly. During 

subsequent solidifi cation, a dense cast 

structure can only occur if the shrinkage 

is offset by feeding from liquid melt. Here, 

a wall thickness extending upwards as a 

connection to the riser may be necessary. 

36 


Another possible way of avoiding material 

accumulations is to loosen the nodes. 

At points where fi ns cross, a mass accumulation 

can be prevented by staggering 

the wall layout. 

The corners where walls or fi ns meet 

should be provided with as large transi- 

tions as possible. Where walls of different 

thickness meet, the transitions should 

be casting-compliant. 

Where the casting size and process 

permit, bores should be pre-cast. This 

improves the cross-section ratio and 

structural quality. 

Apart from the points referred to above, 

a good design also takes account of 

practical points and decorative appear- 

ance as well as the work procedures 

and machining which follow the actual 

casting operation. 

Fettling the casting, i.e. removing the 

riser and feeders, must be carried out as 

effi ciently as possible. Grinding should 

be avoided where possible. Reworking 

and machining should also be easy to 

carry out. Machining allowances are to 

be kept as small as possible. 

Essential inspections or quality tests 

should be facilitated by constructive 

measures.

Solidifi cation simulation and thermography 

Solidifi cation simulation 

A basic aim in the manufacture of cast- 

ings is to avoid casting defects while 

minimising the amount of material in the 

recycling circuit. 

Optimisation of the manufacture of cast- 

ings with regard to casting geometry, 

gating and feeding system and cast- 

ing parameters can be achieved via 

numerical simulation of die fi lling and 

the mechanisms of solidifi cation on the 

computer. Casting defects can thus be 

detected in good time and the casting 

design and casting system optimised 

before the fi rst casting operation takes 

place. In principle, fl ow and thermal con- 

duction phenomena which occur during 

casting can be calculated numerically 

using simulation programmes. 

In calculation models, the casting and 

die geometry – which fi rst of all must be 

available in a CAD volume model – is thus 

divided into small volume elements (Finite 

Difference Method). The fl ow velocities 

and temperatures in the individual volume 

elements are then calculated using 

a numerical method. 

Possible positive effects of simulation 

calculations include: 

Optimisation of the casting before 

casting actually takes place 

Avoiding casting defects 

Optimisation of the feeding system 

(reducing material in the recycling 

circuit) 

Optimisation of the casting 

process (reducing cycle times) 

Increasing process stability 

Visualisation of the die-fi lling and 

solidifi cation process. 

A simulation programme does not opti- 

mise on its own and can not, and should 

not, replace the experienced foundry- 

man. To exploit the potential of die-fi lling 

and solidifi cation simulation to the full, 

it should be applied as early as possible, 

i.e. already at the design stage of 

the casting. 

Thermography 

Even after a casting goes into volume 

production, it is often desirable and nec- 

essary to optimise the casting process 

and increase process stability. Besides 

the aforementioned solidifi cation simula- 

tion, periodic thermal monitoring of the 

dies by means of thermography is used 

in particular. 

In this process, a thermogramme of the 

die or casting to be investigated is made 

with the aid of an infrared camera. This 

way, the effectiveness of cooling, e.g. in 

pressure or gravity die casting, can be 

checked or optimised and the optimum 

time for lifting determined. 


Avoiding casting defects 

As shown in Table 4, there are two 

phenomena which – individually or in 

combination – can lead to defects in 

emergent castings: 

1. The continuous (new) formation of 

oxides in the liquid state and 

2. volume contraction during the transition 

from liquid to solid state. 

During transition from liquid to solid 

state, the dissolved hydrogen in the melt 

precipitates and, on interacting with oxides, 

causes the well-known problem of 

microporosity or gas porosity. 

The task of melt management and 

treatment is to keep oxide formation 

and, consequently, the dangers to cast 

quality within limits. Information about 

this is provided in the sections on “Melt 

38 


quality and melt cleaning” as well as 

“Methods for melt monitoring” and “Se- 

lecting the casting process”. Here are a 

few key points: 

Use good quality ingots 

Quality-oriented melting technology 

and equipment 

Correct charging of the ingots 

(dry, rapid melting) 

Temperature control during 

melting and casting 

Melt cleaning and melt control 

Safety measures during treatment, 

transport and casting 

Volume contraction during the transition 

from liquid to solid state can - depending 

on the casting alloy - be up to 7 % 

volume. Under unfavourable conditions, 

part of this volume difference can be the 

cause of defects in castings, e.g. shrink 

marks, shrink holes, pores or tears. To 

produce a good casting, the possibility 

of feeding additional molten metal into 

the contracting microstructure during 

solidifi cation must exist. In pressure 

casting processes, this occurs by means 

of pressurisation; in gravity die casting, 

this is done primarily by feeding. 

The type of solidifi cation is also impor- 

tant when considering suitable casting/ 

technical measures. In AlSi casting al- 

loys with approx. 13 % Si, a frozen shell 

forms during solidifi cation while, in hy- 

poeutectic AlSi casting alloys as well 

as in AlMg and AlCu casting alloys, a 

predominantly dendritic or globular so- 

lidifi cation occurs. 

In gravity die casting processes, the 

feeders are laid out in particularly critical 

or thick areas of the casting. The feed- 

ers require hot metal in appropriately 

large volumes to execute their task. The 

combination of feeding and cooling is 

useful. Heat removal to accelerate and 

control solidifi cation at the lower end 

of the casting or in solid areas can be 

effected by means of metal plates or 

surface chills (cooling elements).

As already shown in the section on cast- 

ing processes, an uncontrolled or tur- 

bulent fi lling of the die cavity can have a 

negative infl uence on the quality of the 

casting. A gating system which allows 

the solidifi cation front to be controlled 

upwards through the casting from the 

bottom up to the feeder is helpful. A 

good casting system, e.g. side stand 

pipe-slit gate, begins the fi lling in the 

lower part of the die and always layers 

the new hot metal on the lower, already 

solidifi ed part and also supplies the 

feeder with hot metal. 

A casting system of this type can par- 

tially cushion the negative effect caused 

by volume contraction while conducting 

the molten metal in such a way that fresh 

oxidation of the melt due to turbulence 

is avoided. 

Classifi cation of casting defects 

Source of defect Consequences Optimisation 

for the casting possibilities 

Oxidation and Pores Melt treatment 

hydrogen- Aeration and degassing 

absoption Inclusions Melting and 

Leakiness casting temperature 

Surface defects Filter 

Machining 

Loss of strength 

and elongation 

Volume contraction Cavity Gating system 

Shrinkage Solidifi cation control 

Aeration Feeding 

Leakiness Grain refi nement 

Loss of strength Modifi cation 

and elongation 

Two methods can be used to reduce 

the number of defective parts due to 

porosity: In hot isostatic pressing (HIP), 

porous castings are subjected to high 

pressure at elevated temperatures so 

that shrinkage and pores inside the castings 

are reduced; they do not, however, 

completely disappear. A second and 

less costly possibility is the sealing of 

castings by immersing them in plastic 

solutions. The shrinkage and pores, 

which extend to the surface, are fi lled 

with plastic and therefore sealed. 

Table 4 


Heat treatment of aluminium castings 

Heat treatment gives users of castings 

the possibility of specifi cally improv- 

ing the mechanical properties or even 

chemical resistance. Depending on the 

casting type, the following common and 

applied methods for aluminium castings 

can be used: 

Stress relieving 

Stabilising 

Homogenising 

Soft annealing 

Age-hardening. 

The most important form of heat treatment 

for aluminium castings is artifi cial 

ageing. Further information is provided 

below. 

40 


Ageing time [h] 

Metallurgy – fundamental principles 

For age-hardening to take place, there 

must be a decreasing solubility of a par- 

ticular alloy constituent in the α-solid so- 

lution with falling temperature. As a rule, 

age-hardening comprises three steps: 

In solution annealing, suffi cient amounts 

of the important constituents for age- 

hardening are dissolved in the α-solid 

solution. 

With rapid quenching, these constituents 

remain in solution. Afterwards, the parts 

are relatively soft. 

Figure 11.1 

Yield strength of 

gravity die cast test bars (Diez die) in Al Si10Mg alloy 

Yield strength R p0,2 

[MPa] 

280 

240 

200 

160 

120 

0 

0 2 4 6 8 10 12 14 16 

160 °C 180 °C 200 °C 

As-cast state 

In ageing, mostly artifi cial ageing, precipitation 

of the forcibly dissolved components 

takes place in the form of small 

sub-microscopically phases which cause 

an increase in hardness and strength. 

These tiny phases, which are technically 

referred to as “coherent or semicoherent 

phases”, represent obstacles 

to the movement of dislocations in the 

metal, thereby strengthening the previously 

easily-formable metal. 

The following casting alloy types are 

age-hardenable: 

Al Cu 

Al CuMg 

Al SiMg 

Al MgSi 

Al ZnMg. 

Figure 11.2 

Elongation of 


Elongation A5 [%] 

5 

4 

3 

2 

1 

0 

0 2 4 6 8 10 12 14 16 


160 °C 180 °C 200 °C 

As-cast state

Solution annealing 

To bring the hardened constituents into 

solution as quickly as possible and in a 

suffi cient amount, the solution anneal- 

ing temperature should be as high as 

possible with, however, a safety margin 

of approx. 15 K to the softening point 

of the casting alloy in order to avoid incipient 

fusion. For this reason, it is often 

suggested that casting alloys containing 

Cu should undergo step-by-step solution 

annealing (at fi rst 480 °C, then 520 °C). 

The annealing time depends on the wall 

thickness and the casting process. Com- 

pared with sand castings, gravity die cast- 

ings require a shorter annealing time to 

dissolve the constituents suffi ciently due 

to their fi ner microstructure. In principle, 

an annealing time of around one hour 

Figure 11.3 

Tensile strength of 


Tensile strength Rm [MPa] 

360 

320 

280 

240 

200 

160 

0 2 4 6 8 10 12 14 16 


160 °C 180 °C 200 °C 

As-cast state 

suffi ces. The normally longer solution 

annealing times of up to 12 hours, as 

for example in Al SiMg alloys, produce 

a good spheroidising or rounding of the 

eutectic silicon and, therefore, a marked 

improvement in elongation. 

The respective values for age-hardening 

temperatures and times for the individual 

casting alloys can be indicated on the 

respective data sheets. 

During the annealing phase, the strength 

of the castings is still very low. They must 

also be protected against bending and 

distortion. With large and sensitive castings, 

it may be necessary to place them 

in special jigs. 

Quenching 

Hot castings must be cooled in water as 

rapidly as possible (5-20 seconds de- 

pending on wall thickness) to suppress 

any unwanted, premature precipitation of 

the dissolved constituents. After quench- 

ing, the castings display high ductility. 

This abrupt quenching and the ensuing 

increase in internal stresses can lead 

to distortion of the casting. Parts are 

often distorted by vapour bubble pressure 

shocks incurred during the rapid 

immersion of hollow castings. If this is 

a problem, techniques such as spraying 

under a water shower or quenching in 

hot water or oil have proved their value 

as a fi rst cooling phase. 

Nevertheless, any straightening work 

necessary at this stage should be carried 

out after quenching and before ageing. 


Ageing 

The procedure of ageing brings about 

the decisive increase in hardness and 

strength of the cast structure through 

the precipitation of the very small hardening 

phases. Only after this does the 

part have its defi nitive service properties 

and its external shape and dimensions. 

Common alloys mostly undergo artifi cial 

ageing. The ageing temperatures and 

times can be varied as required. In this 

Figure 11.4 

Brinell hardness of 


Brinell hardness 

[HB] 

160 

140 

120 

100 

80 

60 

0 2 4 6 8 10 12 14 16 

42 



160 °C 180 °C 200 °C 

As-cast state 

way, for example, the mechanical prop- 

erties can be adjusted specifi cally to at- 

tain high hardness or strength although, 

in doing this, relatively lower elongation 

must be reckoned with. Conversely, high 

elongation can be also achieved while 

lower strength and hardness values will 

be the result. When selecting the ageing 

temperatures and times, it is best to 

refer to the ageing curves which have 

been worked out for many casting alloys 

(Figures 11.1-11.4). 

Infl uence of Magnesium 

on the tensile strength (Diez bars) 

In Al SiMg casting alloys, a further possibility 

of specifi cally adjusting strength 

and elongation arises from varying the 

Mg content in combination with different 

heat treatment parameters (Figure 12). 

Tensile strength Rm Alloy Al Si7 auf 99.9 base 

[MPa] 

300 

+ 200 ppm Sr + 1 kg/mt Al Ti3B1 

n=5 

250 

200 

150 

100 

50 

0 

0 0.1 0.2 0.3 0.4 0.5 0.6 

8 h to 525 °C, H 2 O +6 h to 160 °C 

Magnesium [%] 

8 h to 525 °C, H 2 O As-cast state 

Figure 12

If the heat treatment does not work fi rst 

time, it can be repeated beginning with 

solution annealing. By doubling the solution 

time, a coarsening of the eutectic 

silicon can arise in the grain structure. 

Since the solution treatment is performed 

close to the alloy‘s melting temperature 

and the precipitation rate is highly sensitive 

to variations in ageing temperature, 

it is essential that a high degree 

of consistency and control is assured. 

Procedures used in artifi cial ageing 1) 

Regular maintenance, especially of the 

measuring and control equipment, is 

therefore absolutely essential. 

For slightly higher hardness or strength 

requirements, there is the non-standard 

possibility of “simplifi ed age-hardening”. 

This can be used in gravity die casting 

and pressure die casting when age- 

hardenable alloys are being poured. 

Decisive here is a further rapid cooling 

after ejection from the die, e.g. by immediately 

immersing the part in a bath 

Table 5 

Casting type Example Solution heat treatment Age-hardening 

Temperature Time Temperature Time 

[°C] [h] [°C] [h] 

Al SiMg Al Si10Mg 530 4 - 10 160 - 170 6 - 8 

Al SiCu Al Si9Cu3 480 6 - 10 155 - 165 6 - 2 

Al MgSi Al Mg3Si 550 4 - 10 155 - 175 8 - 0 

Al CuMg 530* 8 - 18 140 - 170 6 - 8 

1) Typical temperature and time values 

* Poss. gradual annealing at approx. 480 °C / approx. 6 h 

of water. Artifi cial ageing in a furnace at 

approx. 170 °C brings about the desired 

increase in hardness and strength. 

The procedure used in artifi cial ageing as 

well as typical temperatures and times 

are shown in Table 5. 


Mechanical machining of aluminium castings 

In general, parts made from aluminium 

casting alloys are easy-machinable. 

This also applies for all metal-cutting 

processes. Low cutting force allows a 

high volume of metal to be removed. The 

surface fi nish of the cast piece depends 

on the machining conditions, such as 

cutting speed, cutting geometry, lubrication 

and cooling. 

The high cutting speeds required in aluminium 

to achieve minimum roughness 

necessitate, with regard to processing 

machines and tools, stable, vibrationfree 

construction and good cutting tools. 

Besides the microstructure – including 

defects, pores or inclusions – the silicon 

content of the casting has a strong effect 

on tool wear. Modifi ed, hypoeutectic 

AlSi casting alloys have, e.g. the highest 

tool time, while hypereutectic aluminium- 

silicon piston casting alloys can cause 

very considerable tool wear. 

44 


With softer materials and also with most 

hypoeutectic AlSi casting alloys, narrow 

tools, i.e. with a large rake angle, cause 

the least possible surface roughness. 

These casting alloys produce narrow- 

spiral or short-breaking turnings. When 

machining aluminium, suitable emul- 

sions with water are used as cooling 

agents and lubricants. Friable and chips 

and fi ne to powdery Si dust arise when 

machining hypereutectic casting alloys. 

In combination with the lubricant, this 

powder produces an abradant which is 

often processed when dry. In some respects, 

the machining of these casting 

alloy types is similar to grey cast iron. 

With workpieces made from Al Si12 

casting alloys with their very soft matrix, 

a large volume of long curly spirals are 

produced. In addition, the plastic material 

tends to build up edges on the tool. 

This leads to lubrication and, as a result, 

a poor surface appearance. When this 

occurs, it often gives the machinist the 

subjective impression of bad machinability 

although tool wear is not the cause 

in this case. 

High-speed steel and hard metal or 

ceramic plates are used as cutting tool 

materials; for microfi nishing, diamonds 

are often utilised. 

The following machining allowances are 

given for the main casting processes: 

sand castings: 1.5-3 mm 

gravity die castings: 0.7-1.5 mm 

pressure die castings: 0.3-0.5 mm. 

In order to minimise value losses, turnings 

and chips should be sorted out according 

to casting alloy type and stored possibly 

in briquettes. In addition, dampness, 

grease and free iron reduce the value of 

chips and turnings. Aluminium chips and 

turnings are not hazardous materials and 

there is no risk of fi re during storage. 

When grinding aluminium parts, explosion- 

proof separation of the dust is stipulated.

Welding and joining aluminium castings 

Suitability and behaviour 

Similar to most wrought aluminium alloys, 

castings made from aluminium casting 

alloys can, in principle, also be joined by 

means of fusion welding. Near-eutectic 

and hypoeutectic aluminium-silicon cast- 

ing alloys are the best to weld. Poor to 

unweldable are parts made from Al Cu4Ti 

alloys types since the Cu-content can 

cause the casting alloy to crack during 

welding. In AlMg casting alloys, the ten- 

dency to tearing must be counteracted 

by selecting a suitable weld fi ller. 

Applications in the aluminium sector 

Although near net shape casting gives 

the designer the greatest possible freedom 

in the design of castings, welding is 

becoming increasingly important for the 

joining of aluminium cast components, 

either for welding two or more easy-tocast 

parts (e.g. half shells) – whereas 

they would be diffi cult to cast as one – 

to form hollow bodies on the one hand 

or for joining extruded sections or sheet 

to castings to give a subassembly on 

the other, such as the case in vehicle 

construction, lamp posts, lamp fi ttings 

and heat exchangers. 

The production welding sector should 

not be underestimated, e.g. for repairing 

defects in castings. Besides casting 

defects, there is also the possibility of 

correcting dimensional discrepancies, 

removing wear by build-up welding and 

repairing broken components. 

Welding processes 

The most frequently used fusion weld- 

ing processes for joining castings are 

metallic-insert-gas welding (MIG weld- 

ing) and Tungsten-inert-gas welding 

(TIG welding). 

Metal inert-gas welding (MIG welding) 

In MIG welding, an inert-gas arc weld- 

ing process, a continuous arc burns 

between a melting wire electrode and 

the workpiece. The process works with 

direct current, the wire electrode acting 

as the positive pole. The process is carried 

out under an inert gas in order to 

protect the melt area from the hazardous 

infl uences of the oxygen contained 

in air and moisture. Argon and/or helium, 

both inert gases, are used as shielding 

gases. Normally, it is cheaper to weld 

using argon. The process is suitable 

for both manual welding and for fully- 

mechanised and automatic welding. In 

fully-mechanised and automatic welding, 

both the power source and burner are 

water-cooled. With the wire electrode 

acting as the positive pole, the energy 

density is so high that it is able to break 

open the tenacious and high-melting 

oxide layer by means of local, explosive 

metal vaporisation underneath the oxide. 

With appropriate heat conduction, 

it is possible to achieve a relatively narrow 

heat-affected zone with satisfactory 

strength and elongation values. 

A further development of MIG welding is 

represented by MIG pulse welding. Here, 

the welding current alternates between a 

so-called pulsed current and background 

current. Using this process, it is possible 

to carry out diffi cult tasks, i.e. thin wall 

thicknesses (1 mm) and out-of-position 

work (overhead). 

Today, MIG welding is the most frequently 

used aluminium welding process because, 

in addition to its easy manipulation, 

the investment and running costs 

are favourable. 


Tungsten-insert-gas welding 

(TIG welding) 

In TIG welding, an inert-gas shielded 

arc welding process, an arc burns continuously 

between a non-consumable 

electrode made of a tungsten alloy and 

the casting. Alternating current is normally 

used when welding aluminium. The 

welding fi ller is fed in separately from 

outside either by hand or mechanically. 

The process is carried out under an inert 

gas in order to protect the melt area 

from the hazardous infl uences of the 

oxygen contained in air and moisture. 

Argon and/or helium, both inert gases, 

are used as shielding gases. Welding is 

usually carried out with alternating current 

and argon which is cheaper. This is 

primarily a manual welding process but 

there is a possibility to work with a full 

degree of mechanisation. In TIG welding, 

the power source and the burner are 

both water-cooled. By using alternating 

current, the tenacious and high-melting 

oxide layer is broken open during welding, 

similar to the MIG process. Welding 

normal diameter material with direct 

current and a reverse-polarity tungsten 

electrode would lead to destruction due 

to electric overload. The electrode diameter, 

however, can not be increased since 

the current density required for welding 

is no longer suffi cient. 

46 


In one process variant, which has an 

electrode with negative polarity as in the 

welding of steel, welding is carried out 

using direct current under a helium shield. 

Compared with argon, helium displays 

better thermal conductivity so that less 

current is required to break open the oxide 

layer. Consequently, the electrode is 

not overloaded. In TIG welding, there are 

also process variants which work with 

the pulsed-current technique. 

With regard to freedom from porosity, 

the cleanest seams can be achieved 

using TIG welding. One disadvantage 

of the TIG welding process, however, is 

the high local energy input. This leads 

to considerable softening of the zone 

adjacent to the weld which is also the 

case with MIG welding. TIG welding, for 

example, is an excellent process for the 

repair of small casting defects. Compared 

with the MIG process, however, 

TIG welding operates at lower speeds. 

Other thermal joining processes 

The group of so-called “pressure welding 

processes” also includes friction stear 

welding (FSW) which is frequently used 

for welding aluminium castings. Since this 

welding process works without any fi ller 

material, it is possible to join materials 

together which are not fusion-weldable 

since they would form brittle inter-metallic 

phases. By means of friction welding, 

aluminium and steel, for example, can 

be joined together. 

The principle behind the process is to heat 

the workpieces up to a pasty condition 

followed by subjecting them to strong 

compression. A weld upset is thus developed 

and, if necessary, subsequently 

machined. The heating is done by rotating 

one or both parts and fi nally pressing 

them against each other until they 

stop moving. It even allows workpieces 

of circular and square cross-sections to 

be joined together. 

As a result of the rotary movement and 

in order to keep the compression load 

from increasing too much, a certain crosssectional 

area may not be exceeded. 

Another welding process is represented 

by electron beam welding. Particular interest 

is being shown in this process at 

the moment for the welding of aluminium 

pressure die castings.

The process operates mostly under high 

vacuum. There are also process variants 

which work under partial vacuum and 

atmosphere although in these the advan- 

tages of this welding process, namely the 

production of narrower seams even with 

thick workpieces, are extensively lost. 

The welding of workpieces takes place 

without fi ller material. The welding energy 

is imparted by means of a bundled 

electron beam which is directed at the 

welding point. The electron beams are 

generated like those of a cathode ray 

tube (television) in a high vacuum. Using 

electron-optical focussing, different distances 

to the workpiece can be had with 

this equipment, even when the workpiece 

has undulating contours. Welding inside 

closed containers is possible. 

In addition to diffi cult-to-weld pressure 

die castings, e.g. inlet manifolds, this 

process has been successfully used with 

cast semi-fi nished products in heat exchangers 

and in the welding of pistons 

for internal combustion engines. 

Weld preparation 

To produce a sound weld, it is necessary 

to observe certain “rules”. Weld preparation 

must match the welding process 

being used and the wall thicknesses to 

be joined. Excessive oxide formation is 

worked off by metal-cutting. When grinding, 

resin-bonded grinding discs may 

not be used (danger of pore formation). 

Another possible way of removing oxides 

is to etch the component. Grease 

and dirt in the welding area have to be 

removed using suitable means (danger 

of pore formation). Components with 

greater wall thicknesses to be joined 

should be pre-heated before welding. 

Weld fi ller materials 

Weld fi ller materials are standardised. 

The selection of weld fi ller materials is 

guided by the materials of the parts to 

be joined. For the most commonly used 

aluminium materials, such as near- and 

hypoeutectic AlSi casting alloys as 

well as age-hardenable Al Si10Mg and 

Al Si5Mg variants, S-Al Si12 and S-Al Si5 

weld fi ller materials are recommended. 

A great danger in welding is the tendency 

of many materials to form cracks during 

the transition from liquid to solid state. 

The cause of these cracks is weld shrink- 

age stresses which occur during cooling. 

Often the low melting point phases of 

the weld fi ller materials are insuffi cient 

to “heal” the cracks arising. Through the 

selection of a softer weld fi ller material 

with a larger share of low melting point 

phases, this danger is reduced. In doing 

this, however, the optimum strength 

properties in the weld seam must be 

frequently foregone. 

The decorative anodisation of a welded 

joint with the aforementioned fi ller materials 

is not possible because the weld 

seam would appear dark. Technical anodic 

oxidation for protective and adhesive 

purposes is, however, always possible. 


Surface treatment: corrosion 

and corrosion protection 

Aluminium casting alloys – like wrought 

aluminium alloys – owe their corrosion 

resistance to a thin, tenacious coating 

layer of oxides and hydroxides. In the pH 

range from 4.5 to 8.5, this oxide layer is 

practically insoluble in aqueous media 

and aluminium casting materials suffer 

only negligible mass disappearance. 

This passivity can, however, be annulled 

locally at weak points in the oxide layer 

due to the action of water containing 

chloride. Since the aqueous medium, 

e.g. weather, only acts periodically, a 

protective oxide layer forms again at 

small, local corrosion sites, e.g. repassivation 

occurs. Deep pitting corrosion 

can only arise when there is a long-term 

effect from aggressive water containing 

chloride (e.g. sea water). Beside the 

chloride content, the amount of oxygen 

in the water also plays a role; corrosion 

reaction can only occur in neutral media 

(pH = 4.5-8.5) in the presence of 

oxygen. The remedy for this can come 

in the form of passive protection by 

coating or by means of active cathodic 

corrosion protection using a sacrifi cial 

anode, for example. 

Magnesium as an alloying element 

causes the formation of a thicker oxide 

layer containing MgO and, consequently, 

provides greater corrosion protection 

against water containing chlorides and 

48 


slightly alkaline media (e.g. ammonia 

solutions) since magnesium oxide in 

contrast to aluminium oxide is insoluble 

in alkaline solutions. 

Copper as an alloying element causes 

a deterioration in corrosion properties. 

This increases slightly with a rising Cu- 

content in the range below 0.2 % copper, 

above 0.2 to 0.4 % more strongly. 

Already with a Cu-content of 0.2 %, 

permanent action from aqueous solutions 

containing chlorine can have a very 

negative effect on corrosion behaviour. 

The negative infl uence of iron on cor- 

rosion behaviour is not as distinctive 

as that of copper. With an Fe-content 

of up to 0.6 %, there is no signifi cant 

deterioration in the corrosion behaviour 

of casting alloys. 

The surface treatment of aluminium cast 

products is carried out to improve their 

corrosion resistance, for decorative 

purposes or to increase the strength 

of the components. 

A homogeneous, non-porous cast struc- 

ture free from shrink holes and cracks 

makes coating easier. The quality of the 

coating is infl uenced decisively by the 

pre-treatment. 

Wiping, immersion and steam degreasing 

(in that order) produce increasingly 

grease-free surfaces without removing 

the surface oxide fi lm. Grinding, brush- 

ing, abrasive blasting or polishing do not 

remove the oxide fi lm completely and, 

as a rule, act as a preparation to further 

surface treatment. Possible sources of 

defects leading to subsequent faults 

comprise the use of brushes made of 

brass or non-stainless steel as well as 

sand or steel shot. 

When grinding, the use of ceramic 

grinding elements without further pretreatment 

frequently leads to good paint 

adhesion. One precondition is that no 

fi nes from the grinding elements are 

pressed into the surface of the casting. 

Chemical degreasing agents with 

a pickling or etching effect remove the 

oxide layer and, as a consequence, all 

impurities. It is also worth mentioning 

that there is also matt or bright pickling 

before anodic oxidation to produce a 

special surface fi nish. 

Following the alkaline pickling of AlMg 

or AlSi casting alloys, the pickling fi lm 

must be removed by means of an acid 

after-treatment with nitric acid, nitric/ 

hydrofl uoric acid or sulphuric/hydrofl 

uoric acid. Instead of alkaline pickling 

with fi nal dipping, it is more benefi cial 

to use an acidic fl uoride-containing 

pickling solution immediately.

Despite careful acid cleaning, a lacquered 

aluminium surface can still display 

adhesive failure after a certain time 

due to environmental effects. Firstly, 

a conversion layer, which forms as a 

result of the reaction between chemicals 

containing chrome and the metal, 

passivates the aluminium surface and 

protects it from the water diffused by 

each layer of lacquer. With respect to 

the promotion of adhesion and corrosion 

inhibition, the almost equivalent 

green and yellow chromate coatings 

have proved their worth over many 

years. A clear chromate coating, preferably 

used under clear lacquer, offers 

slightly less corrosion protection due 

to the layer being thinner. Cr-VI-free 

chromate-phosphate coatings meet the 

requirements of food processing and 

distribution laws and are permitted for 

the pre-treatment of aluminium which 

is used in food production, processing 

and packaging. 

A chrome-free epoxy primer should 

be mentioned as a possible but also 

qualitatively less favourable alternative. 

A precondition for the effectiveness of 

this alternate process, however, is also 

the removal of the aluminium oxide layer 

by chemical or mechanical means. 

Of the unlimited number of application 

techniques used for volume lacquering, 

electrostatic powder coating, whirl sin- 

tering and electrophoretic dip coating 

are to be stressed in particular because 

of their environmental soundness, in 

addition to the dip coating and spray- 

ing (air, airless and electrostatic) of wet 

paint containing solvents. 

With the aid of anodic oxidation, the 

fi nish achieved using mechanical or 

chemical surface treatment can be con- 

served permanently. These anodically 

produced oxide layers are connected 

solidly to the aluminium and, in contrast 

to lacquering, the surface structure of 

the original metal is unchanged. This 

can prove disadvantageous, especially 

in pressure die casting. In today‘s 

widely-used sulphuric acid anodising 

process, the anodically-formed oxide 

layers become resistant to touch (e.g. 

fi nger marking) and abrasion resistant 

after sealing in hot water and possess 

good electric strength. The appearance 

of anodically-oxidised aluminium castings 

is considerably infl uenced by the 

alloy composition and the microstructural 

condition. For decorative purposes, 

Al Mg3H, Al Mg3, Al Mg3Si, Al Mg5, 

Al Mg5Si and Al 99.5 and/or Al 99.7 

casting alloys have proved their worth. 

A decorative anodic oxidation of alloys 

with an Si-content > 1 % is not possible 

(with the exception of Al Si2MgTi). 

The possibility of producing coloured 

oxide layers also exists by means of dip 

painting, electrolytic colouring and integral 

colouring in special electrolytes 

(integral process). 

For surfaces which have to meet particular 

requirements with regard to hardness, 

resistance to abrasion and wear, sliding 

capacity and electric strength, the 

special possibility of using hard anodising 

should be taken into consideration. 


Information on physical data, strength properties 

and strength calculations 

The SI unit for force is the Newton (N). 

Strength, or proof stress, is expressed in 

“MPa” (Mega Pascal). The Brinell hard- 

ness of aluminium parts is excluded from 

this regulation. 

For the tensile strength, 0.2 proof stress, 

elongation and Brinell hardness of cast- 

ings, DIN EN 1706 contains only binding 

minimum values at room temperature 

for separately-cast test bars using sand 

casting, gravity die casting and invest- 

ment casting. The mechanical values 

for pressure die cast samples are not 

binding and are included only for information. 

The values for fatigue strength 

or endurance are valid for the best available 

casting process and again are only 

for information. For samples taken from 

the casting, DIN EN 1706 sets out the 

following: with respect to the 0.2 proof 

stress and tensile strength, the values 

reached in castings can be above the 

set values in the tables (for separatelycast 

test pieces) but not below 70 % of 

these set values. With regard to elongation, 

the values determined for the 

castings can be above the set values 

in the tables (for separately-cast test 

pieces) or at certain critical points up 

to 50 % below these values. Individual 

details about the mechanical, physical 

and other properties as well as the approximate 

working fi gures can be taken 

from the casting alloy sheets. 

50 


The actual values reached in the casting 

depend on the casting/technical measures 

taken, the solidifi cation speed and 

also, where applicable, the heat treat- 

ment. When the end product has to meet 

special requirements, an appropriate 

casting alloy is required which, corre- 

spondingly, also incurs higher casting/ 

technical expenses. A few details for 

calculating the strength of constructions 

which are subjected to static stress are 

given below. With dynamic stress, lower 

values are estimated. 

Surface pressure: 

p = approx. 0.8 R [MPa] 

p0,2 

Shear strength: 

B = approx. 0.5 R [MPa] 

p0,2 

Modulus of elasticity in shear: 

G = approx. 0.4 modulus of 

elasticity [GPa] 

Modulus of elasticity: 

E = approx. 70 GPa 

Yield strength of gravity die cast samples 

Strength at varying temperatures 

At low temperatures, the strength and 

elongation values of aluminium parts 

scarcely change. Due to the crystal 

structure of aluminium alloys, no sharp 

decrease in impact ductility can occur 

at low temperatures – as can happen 

with some ferrous metals. 

At higher temperatures, the strength and 

hardness values decrease while elongation 

increases. Up to approx. +150 °C, 

these changes are relatively small. With 

further increases in temperature, strength 

and hardness decrease even more and 

elongation rises. Table 6 depicts the 0.2 

proof stress values for gravity die cast 

samples at various test temperatures. 

Table 6 

Alloy / Temper Yield strength Rp0,2 [MPa] 

-100 °C +20 °C +100 °C +200 °C +250 °C 

Al Mg3Si T6 160 150 140 60 30 

Silumin F 120 80 60 40 30 

Al Si12Cu F 110 90 80 35 30 

Al Si8Cu3 F 120 100 90 50 25 

Silumin-Kappa F 90 80 70 50 30 

Al Mg5Si T6 130 120 110 100 70 

Al Si18CuNiMg F 180 170 150 100 80 

Al Si12CuNiMg F 200 190 170 100 70 

Al Si10MgCu T6 220 200 170 80 35 

Pantal 7 T6 215 210 180 80 30 

Silumin-Beta T6 220 210 200 80 30 

Pantal 5 T6 220 210 200 80 30

Notes on the casting alloy tables 

The following tables contain all standard- 

ised casting alloys in accordance with 

DIN EN 1676 as well as other common 

non-standardised alloys with details of 

their chemical composition. Provided that 

deviations are envisaged for castings, 

the corresponding details (in conformity 

with DIN EN 1706) are shown in brackets. 

Where available, the well-known and very 

commonly used VDS numbers (e.g. 231, 

226 etc.) are given in these lists. 

The aluminium casting alloys are arranged 

into seven families according to their typical 

casting and alloying similarities. The 

data, properties, rankings and standard 

values of the casting alloys, or the castings 

subsequently made from them, have been 

taken from DIN EN 1676 and 1706 or are 

based on these standards in the case of 

non-standardised alloys. The details are 

included for information only and do not 

represent any guarantees. 

Thermal and electrical conductivity are 

dependent on the chemical composition 

within the given specifi cation, solidifi ca- 

tion conditions and temper. In order to 

produce a casting with high conductivity, 

it is necessary to keep the content of alloying 

and accompanying elements low 

within the specifi cation. 

The following designation 

abbreviations are used in DIN EN 1676: 

A Aluminium 

B Ingots (solid or liquid metal) 

In DIN EN 1706, the following 

abbreviations refer to product 

designations: 

A Aluminium casting alloy 

C Casting 

The following abbreviations are used 

for the various casting processes: 

S Sand casting 

K Gravity die casting 

D Pressure die casting 

L Precision casting 

In DIN EN 1706, the following symbols 

apply for material conditions: 

F as cast 

O annealed 

T1 controlled cooling from casting 

and naturally aged 

T4 solution heat-treated and naturally 

aged where applicable 

T5 controlled cooling from casting 

and artifi cially aged or over-aged 

T6 solution heat-treated and fully 

artifi cially aged 

T64 solution heat-treated and artifi cially 

under-aged 

T7 solution heat-treated and artifi cially 

over-aged (stabilised) 

Chemical composition 

(all data in wt.-%) 

Casting characteristics and 

other properties 

Physical properties 

Mechanical properties at room 

temperature +20 °C 

Heat treatment of aluminium 

castings 

Mechanical properties of gravity 

die cast samples 

Processing guidelines 


Overview: Aluminium casting alloys 

by alloy group 

Eutectic aluminium-silicon casting alloys 

Chemical composition (all data in wt.-%) 

Alloy 

Numerical Other 

denomination 1) / 

VDS-No. 

Si Fe Cu Mn Mg Cr Ni Zn Pb Sn Ti indiv. total Others 

Silumin min 12.5 

max 13.5 0.15 0.02 0.05 0.05 0.07 0.15 0.03 0.10 Na 

Al Si12(a) min 10.5 

max 13.5 0.40 0.03 0.35 0.10 0.15 0.05 0.15 Na 

(0.55) (0.05) 

44200 / 230 

Al Si12(b) min 10.5 

max 13.5 0.55 0.10 0.55 0.10 0.10 0.15 0.10 0.15 0.05 0.15 

(0.65) (0.15) (0.20) 

44100 

Al Si12(Fe)(a) min 10.5 0.45 

max 13.5 0.9 0.08 0.55 0.15 0.15 0.05 0.25 

(1.0) (0.10) 

44300 / 230D 

Al Si12(Fe)(b) min 10.0 0.45 

max 13.5 0.9 0.18 0.55 0.40 0.30 0.15 0.05 0.25 

(1.0) (0.20) 

44500 

Al Si12(Cu) min 10.5 0.05 

max 13.5 0.7 0.9 0.55 0.35 0.10 0.30 0.55 0.20 0.10 0.15 0.05 0.25 

(0.8) (1.0) (0.20) 

47000 / 231 

Al Si12Cu1(Fe) min 10.5 0.6 0.7 

max 13.5 1.1 1.2 0.55 0.35 0.10 0.30 0.55 0.20 0.10 0.15 0.05 0.25 

(1.3) (0.20) 

47100 / 231D 

Values in brackets are valid for castings according to DIN EN 1706: 2010 

1) According to DIN EN 1676: 2010 

Near-eutectic wheel casting alloys 


Alloy 


denomination 1) Si Fe Cu Mn Mg Cr Ni Zn Pb Sn Ti indiv. total Others 

Silumin-Kappa Sr min 10.5 0.05 

max 11.0 0.15 0.02 0.10 0.25 0.07 0.15 0.03 0.10 Sr 

Silumin-Beta Sr min 9.0 0.20 

max 10.5 0.15 0.02 0.10 0.45 0.07 0.15 0.03 0.10 Sr 

Al Si11 min 10.0 

max 11.8 0.15 0.03 0.10 0.45 0.07 0.15 0.03 0.10 Sr 

(0.19) (0.05) 

44000 



52 


The 10 per cent aluminium-silicon casting alloys 


Alloy 



VDS-No. 


Silumin-Beta / Al Si9Mg min 9.0 0.30 

(0.25) 

max 10.0 0.15 0.03 0.10 0.45 

(0.19) (0.05) (0.45) 0.07 0.15 0.03 0.10 Na 

43300 

Al Si10Mg(a) min 9.0 0.25 

(0.20) 

max 11.0 0.40 0.03 0.45 0.45 0.05 0.10 0.05 0.05 0.15 0.05 0.15 Na 

(0.55) (0.05) (0.45) 

43000 / 239 

Al Si10Mg(b) min 9.0 0.25 

(0.20) 

max 11.0 0.45 0.08 0.45 0.45 0.05 0.10 0.05 0.05 0.15 0.05 0.15 

(0.55) (0.10) (0.45) 

43100 

Al Si10Mg(Fe) min 9.0 0.45 0.25 

(0.20) 

max 11.0 0.9 0.08 0.55 0.50 0.15 0.15 0.15 0.05 0.15 0.05 0.15 

(1.0) (0.10) (0.50) (0.20) 

43400 / 239D 

Al Si10Mg(Cu) min 9.0 0.25 

(0.20) 

max 11.0 0.55 0.30 0.55 0.45 0.15 0.35 0.10 0.15 0.05 0.15 

(0.65) (0.35) (0.45) (0.20) 

43200 / 233 


max 11.0 0.55 0.08 0.50 0.10 0.05 0.15 0.05 0.05 0.15 0.05 0.15 

(0.65) (0.10) 

44400 

Silumin-Delta min 9.0 0.3 0.3 

max 10.5 0.4 0.02 0.4 0.03 0.07 0.15 0.03 0.10 

Silumin-Gamma min 9.0 0.4 0.15 

max 11.3 0.15 0.02 0.9 0.6 0.10 0.15 0.03 0.10 Sr 

Al Si10MnMg min 9.0 0.40 0.15 

(0.10) 

max 11.5 0.20 0.03 0.80 0.60 0.07 0.15 0.05 0.15 Sr 

(0.25) (0.05) (0.60) (0.20) 

43500 




Overview: Aluminium casting alloys by alloy group 

The 7 und 5 per cent aluminium-silicon casting alloys 


Alloy 



VDS-No. 


Pantal 7 / Al Si7Mg0.3 min 6.5 0.30 

(0.25) 

max 7.5 0.15 0.03 0.10 0.45 0.07 0.18 0.03 0.10 Na / Sr 

(0.19) (0.05) (0.45) (0.25) 

42100 

Al Si7Mg0.6 min 6.5 0.50 

(0.45) 

max 7.5 0.15 0.03 0.10 0.70 0.07 0.18 0.03 0.10 

(0.19) (0.05) (0.70) (0.25) 

42200 

Al Si7Mg min 6.5 0.25 

(0.20) 

max 7.5 0.45 0.15 0.35 0.65 0.15 0.15 0.15 0.05 0.20 0.05 0.15 

(0.55) (0.20) (0.65) (0.25) 

42000 

Pantal 5 min 5.0 0.40 0.05 

max 6.0 0.15 0.02 0.10 0.80 0.07 0.20 0.03 0.10 

Al Si5Mg min 5.0 0.40 0.05 

max 6.0 0.3 0.03 0.4 0.80 0.10 0.20 0.05 0.15 

- / 235 

Al Si5Cu1Mg min 4.5 1.0 0.40 

(0.35) 

max 5.5 0.55 1.5 0.55 0.65 0.25 0.15 0.15 0.05 0.20 0.05 0.15 

(0.65) (0.65) (0.25) 

45300 

Al Si7Cu0.5Mg min 6.5 0.2 0.25 

(0.20) 

max 7.5 0.25 0.7 0.15 0.45 

(0.45) 

0.07 0.20 0.03 0.10 

45500 



54 


Al SiCu casting alloys 


Alloy 



VDS-No. 

Si Fe Cu Mn Mg Cr Ni Zn Pb Sn Ti indiv. total 

Al Si8Cu3 min 7.5 2.0 0.15 0.15 

(0.05) 

max 9.5 0.7 3.5 0.65 0.55 0.35 1.2 0.25 0.15 0.20 0.05 0.25 

(0.8) (0.55) (0.25) 

46200 / 226 

Al Si9Cu3(Fe) min 8.0 0.6 2.0 0.15 

(0.05) 

max 11.0 1.1 4.0 0.55 0.55 0.15 0.55 1.2 0.35 0.15 0.20 0.05 0.25 

(1.3) (0.55) (0.25) 

46000 / 226D 

Al Si11Cu2(Fe) min 10.0 0.45 1.5 

max 12.0 1.0 2.5 0.55 0.30 0.15 0.45 1.7 0.25 0.15 0.20 0.05 0.25 

(1.1) (0.25) 

46100 

Al Si7Cu3Mg min 6.5 3.0 0.20 0.35 

(0.30) 

max 8.0 0.7 4.0 0.65 0.60 0.30 0.65 0.15 0.10 0.20 0.05 0.25 

(0.8) (0.60) (0.25) 

46300 

Al Si9Cu1Mg min 8.3 0.8 0.15 0.30 

(0.25) 

max 9.7 0.7 1.3 0.55 0.65 0.20 0.8 0.10 0.10 0.18 0.05 0.25 

(0.8) (0.65) (0.20) 

46400 

Al Si9Cu3(Fe)(Zn) min 8.0 0.6 2.0 0.15 

(0.05) 

max 11.0 1.2 4.0 0.55 0.55 0.15 0.55 3.0 0.35 0.15 0.20 0.05 0.25 

(1.3) (0.55) (0.25) 

46500 / 226/3 

Al Si7Cu2 min 6.0 1.5 0.15 

max 8.0 0.7 2.5 0.65 0.35 0.35 1.0 0.25 0.15 0.20 0.05 0.15 

(0.8) (0.25) 

46600 

Al Si6Cu4 min 5.0 3.0 0.20 

max 7.0 0.9 5.0 0.65 0.55 0.15 0.45 2.0 0.30 0.15 0.20 0.05 0.35 

(1.0) (0.25) 

45000 / 225 

Al Si5Cu3Mg min 4.5 2.6 0.20 

(0.15) 

max 6.0 0.50 3.6 0.55 0.45 0.10 0.20 0.10 0.05 0.20 0.05 0.15 

(0.60) (0.45) (0.25) 

45100 

Al Si5Cu3 min 4.5 2.6 

max 6.0 0.50 3.6 0.55 0.05 0.10 0.20 0.10 0.05 0.20 0.05 0.15 

(0.60) (0.25) 

45400 



Others 



AlMg casting alloys 


Alloy 



VDS-No. 


Al Mg3(H) min 2.7 

max 0.45 0.15 0.02 0.40 3.2 0.07 0.02 0.03 0.10 B/Be 

Al Mg3 min 2.7 

(2.5) 

max 0.45 0.40 0.03 0.45 3.5 0.10 0.15 0.05 0.15 B/Be 

(0.55) (0.55) (0.05) (3.5) (0.20) 

51100 / 242 

Al Mg3(Cu) min 2.5 

max 0.60 0.55 0.15 0.45 3.2 0.30 0.20 0.05 0.15 B/Be 

- / 241 

Al Mg3Si(H) min 0.9 2.7 

max 1.3 0.15 0.02 0.40 3.2 0.07 0.15 0.03 0.10 B/Be 


(4.5) 

max 0.35 0.45 0.05 0.45 6.5 0.10 0.15 0.05 0.15 B/Be 

(0.55) (0.55) (0.10) (6.5) (0.20) 

51300 / 244 

Al Mg5(Si) min 4.8 

(4.5) 

max 1.3 0.45 0.03 0.45 6.5 0.10 0.15 0.05 0.15 B/Be 

(1.5) (0.55) (0.05) (6.5) (0.20) 

51400 / 245 

Al Mg9(H) min 1.7 0.2 8.5 

max 2.5 0.50 0.02 0.5 10.5 0.07 0.15 0.03 0.10 B/Be 

Al Mg9 min 0.45 8.5 

(8.0) 

max 2.5 0.9 0.08 0.55 10.5 0.10 0.25 0.10 0.10 0.15 0.05 0.15 B/Be 

(1.0) (0.10) (10.5) (0.20) 

51200 / 349 

Al Mg5Si2Mn min 1.8 0.4 5.0 

(4.7) 

max 2.6 0.20 0.03 0.8 6.0 0.07 0.20 0.05 0.15 

(0.25) (0.05) (6.0) (0.25) 

51500 

Al Si2MgTi min 1.6 0.30 0.50 0.07 

(0.45) (0.05) 

max 2.4 0.50 0.08 0.50 0.65 0.05 0.10 0.05 0.05 0.15 0.05 0.15 

(0.60) (0.10) (0.65) (0.20) 

41000 



56 


Casting alloys for special applications 


Alloy 



VDS-No. 


High-strength casting alloys 

Al Cu4Ti min 4.2 0.15 

(0.15) 

max 0.15 0.15 5.2 0.55 0.07 0.25 0.03 0.10 

(0.18) (0.19) (0.30) 

21100 

Al Cu4MgTI min 4.2 0.20 0.15 

(0.15) (0.15) 

max 0.15 0.30 5.0 0.10 0.35 0.05 0.10 0.05 0.05 0.25 0.03 0.10 

(0.20) (0.35) (0.35) (0.30) 

21000 

Al Cu4MnMg min 4.0 0.20 0.20 

(0.15) 

max 0.10 0.15 5.0 0.50 0.50 0.03 0.05 0.03 0.03 0.05 0.03 0.10 

(0.20) (0.50) (0.05) (0.10) (0.10) 

21200 

Al Cu4MgTiAg min 4.0 0.01 0.15 0.5 Ag 

0.4 

max 0.05 0.10 5.2 0.50 0.35 0.05 0.35 0.03 0.10 1.0 

Al Cu5NiCoSbZr min 4.5 0.1 1.3 0.15 **** 

max 0.20 0.30 5.2 0.3 0.10 1.7 0.10 0.30 0.05 0.15 

Piston casting alloys 

Al Si12CuNiMg min 10.5 0.8 0.9 

(0.8) 

0.7 

max 13.5 0.6 1.5 0.35 1.5 1.3 0.35 0.20 0.05 0.15 P 

(0.7) (1.5) (0.25) 

48000 / 260 

Al Si18CuNiMg min 17.0 0.8 0.8 0.8 

max 19.0 0.3 1.3 0.10 1.3 1.3 0.10 0.15 0.05 0.15 P 

****) Co 0.10-0.40 Sb 0.10-0.30 Zr 0.10-0.30 



Continuation of the table on the next page. 





Alloy 



Hyper eutectic casting alloys 

Al Si17Cu4Mg* min 16.0 4.0 0.5 

max 18.0 0.3 5.0 0.15 0.65 0.10 0.10 0.20 0.05 0.15 P 

Al Si17Cu4Mg** min 16.0 4.0 0.45 

(0.25) 

max 18.0 1.0 5.0 0.50 0.65 0.3 1.5 0.15 0.20 0.05 0.25 

(1.3) (0.65) (0.25) 

48100 

Self-hardening casting alloys 

Autodur min 8.5 0.3 9.5 

max 9.5 0.15 0.02 0.05 0.5 10.5 0.15 0.03 0.10 

Autodur (Fe)* min 8.5 0.3 9.5 

max 9.5 0.40 0.02 0.30 0.5 10.5 0.15 0.03 0.10 

Autodur (Fe)** min 7.5 0.25 

(0.20) 

9.0 

max 9.5 0.27 0.08 0.15 0.5 10.5 0.15 0.05 0.15 

(0.30) (0.10) (0.5) 

71100 

Rotor-Aluminium 

Al 99.7E*** min 

max 0.07 0.20 0.01 0.005 0.02 0.004 0.04 Mn+Cr+ 0.03 

V+ Ti= 

0.02 

B 0.04 

Al 99.6E*** min 

max 0.10 0.30 0.01 0.007 0.02 0.005 0.04 Mn+Cr+ 0.03 

V+Ti= 

0.030 

B 0.04 

*) Non-standardised version 

**) According to DIN EN 1706: 2010 

***) According to DIN EN 576 



58 


Eutectic 

aluminium-silicon casting alloys 


Alloy 



VDS-No. 


Silumin min 12.5 

max 13.5 0.15 0.02 0.05 0.05 0.07 0.15 0.03 0.10 Na 

Al Si12(a) min 10.5 

max 13.5 0.40 0.03 0.35 0.10 0.15 0.05 0.15 Na 

(0.55) (0.05) 

44200 / 230 

Al Si12(b) min 10.5 

max 13.5 0.55 0.10 0.55 0.10 0.10 0.15 0.10 0.15 0.05 0.15 

(0.65) (0.15) (0.20) 

44100 

Al Si12(Fe)(a) min 10.5 0.45 

max 13.5 0.9 0.08 0.55 0.15 0.15 0.05 0.25 

(1.0) (0.10) 

44300 / 230D 

Al Si12(Fe)(b) min 10.0 0.45 

max 13.5 0.9 0.18 0.55 0.40 0.30 0.15 0.05 0.25 

(1.0) (0.20) 

44500 

Al Si12(Cu) min 10.5 0.05 

max 13.5 0.7 0.9 0.55 0.35 0.10 0.30 0.55 0.20 0.10 0.15 0.05 0.25 

(0.8) (1.0) (0.20) 

47000 / 231 

Al Si12Cu1(Fe) min 10.5 0.6 0.7 

max 13.5 1.1 1.2 0.55 0.35 0.10 0.30 0.55 0.20 0.10 0.15 0.05 0.25 

(1.3) (0.20) 

47100 / 231D 





Casting characteristics and other properties of castings 

Alloy Fluidity Thermal Pressure As-cast Ageability Corrosion Decorative Weldability Polishability 

Silumin 

Al Si12(a) 

Al Si12(b) 

Al Si12(Fe)(a) 

Al Si12(Fe)(b) 

Al Si12(Cu) 

crack 

stability 

tightness state resistance anodisation 

Al Si12Cu1(Fe) 


Alloy Density E-Modulus Thermal Solidifi cation Coeffi cient Electrical Thermal 

capacity temperature of thermal conductivity conductivity 

at 100 °C expansion 

g/cm3 MPa J/gK °C 10-6 /K 

293 K - 373 K 

MS/m W/(m . k) 

Silumin 2.68 75,000 0.91 ~ 577 21 18 - 24 140 - 170 

Al Si12(a) 2.68 75,000 0.90 ~ 577 20 17 - 24 140 - 170 

Al Si12(b) 20 16 - 23 130 - 160 

Al Si12(Fe)(a) 2.68 75,000 0.90 ~ 577 20 16 - 22 130 - 160 

Al Si12(Fe)(b) 20 16 - 22 130 - 160 

Al Si12(Cu) 2.70 75,000 0.89 ~ 577 20 16 - 22 130 - 150 

Al Si12Cu1(Fe) 2.70 75,000 0.89 ~ 577 20 15 - 20 120 - 150 

60 


Mechanical properties at room temperature +20 °C 

Alloy / Temper Casting method Tensile strength R Yield strength R Elongation A m p0,2 Brinell 

hardness HB 

Fatigue 

resistance 

MPa MPa % MPa 

min min min min 

Silumin F Sand casting 150 70 6 45 60 - 90 

Al Si12(a) F Sand casting 150 70 5 50 60 - 90 

Al S12(b) F Sand casting 150 70 4 50 

Al Si12(Cu) F Sand casting 150 80 1 50 60 - 90 

Silium F Gravity die casting 170 80 7 45 60 - 90 

Al Si12(a) F Gravity die casting 170 80 6 55 60 - 90 

Al Si12(Cu) F Gravity die casting 170 90 2 55 60 - 90 

Al Si12(Fe)(a) F Pressure die casting 240 130 1 60 60 - 90 

Al Si 12(Fe)(b) F Pressure die casting 240 140 1 60 

Al Si12Cu1(Fe) F Pressure die casting 240 140 1 70 60 - 90 

The values apply for separately-cast sample bars in sand and gravity die casting. Mechanical properties of pressure die casting samples are not binding and merely serve 

as information. The values representing vibration testing and/or fatigue strength apply for the best available casting process and merely serve as information. 

Mechanical properties of gravity die casting samples 1) 

Alloy / Temper Tensile strength R m Yield strength R p0,2 Elongation A Brinell hardness HB 

MPa MPa % 

-100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C 

Silumin 220 180 150 110 120 80 60 40 6 8 10 12 50 50 45 35 

Al Si12(a) 220 180 150 110 120 80 60 40 2,5 3 4 10 50 50 45 35 

Al Si12(b) 220 180 150 110 120 80 60 40 2.5 3.4 10 10 50 50 45 35 

Al Si12(Cu) 190 170 110 100 80 35 1 3 8 55 45 25 

1) Mechanical properties in minimum values / values after long-term maintenance of the respective temperature. 

Typical process parameters 

Alloy Casting temperature Contraction allowance 

Sand Gravity Pressure Sand Gravity Pressure 

casting die casting die casting casting die casting die casting 

°C °C °C % % % 

Silumin 670 - 740 670 - 740 620 - 660 1.0 - 1.2 0.5 - 0.8 

Al Si12(a) 670 - 740 670 - 740 1.0 - 1.2 0.5 - 0.8 

Al Si12(Fe)(a) 620 - 660 0.4 - 0.6 

Al Si12(Cu) 670 - 740 670 - 740 1.0 - 1.2 0.5 - 0.8 

Al Si12Cu1(Fe) 620 - 660 0.4 - 0.6 



Application notes 

Universal aluminium casting alloy with 

medium strength; in part, very good elon- 

gation and very good fl ow properties. 

Suitable for thin-walled, complicated, 

pressure-tight, vibration- and impact- 

resistant constructions. 

Properties and processing 

From the range of AlSi casting alloys, 

this type of alloy containing 13 % silicon 

has the best fl uidity. In some respects, 

the behaviour of the casting alloys in this 

range represents a special case. Some 

advice is provided below. 

In the case of free solidifi cation, e.g. a 

dense, bevel-shaped surface, the so- 

called “hammer blow”, forms on the top 

of the ingot. This type of solidifi cation is 

“shell-forming”, i.e. the crystallisation of 

the subsequent casting begins with the 

formation of a solid shell which then grows 

towards the middle of the cast wall. In 

this type of casting alloy, there are only 

two states, i.e. “solid” and “liquid”. Full 

solidifi cation of a casting takes place 

at the eutectic temperature of approx. 

577 °C). During the solidifi cation process, 

the volume can contract by up to 7 %. 

62 


The shell thickness does not decrease. 

If the fl ow of liquid metal is interrupted 

in the middle wall region during feeding, 

a coarse cavity can evolve. (Additional 

notes also provided in the sections entitled 

“Infl uencing the microstructural 

formation of aluminium castings” and 

“Avoiding casting defects”.) 

This type of aluminium casting alloy can 

only be modifi ed with sodium. Sodium 

modifi cation is indicated for sand cast- 

ings and gravity die castings if particular 

requirements are placed on elongation 

of the microstructure (see Figure 2). As 

a general rule, casting alloys for use in 

sand and gravity die casting are offered 

in a slightly modifi ed version. Chemical 

resistance as well as resistance to weath- 

ering and a marine climate increase with 

the purity of the casting alloy used. A pri- 

mary silicon casting alloy thus meets the 

highest requirements in a variety of fi elds 

of application, e.g. in the food industry 

or in shipbuilding. The elongation of the 

cast structure is signifi cantly determined 

by the iron content and other impurities. 

The demand for high proof stress values 

in the casting often requires the use of 

primary casting alloys with the lowest 

possible content of iron and impurities. 

Heat treatment 

In the case of sand and gravity die cast- 

ings made from casting alloys low in 

Cu and Mg, a selective improvement 

in ductility can be achieved. This is ef- 

fected by means of solution annealing at 

520-530 °C with subsequent quenching 

in cold water. 

Comments 

The DIN EN 1676 and DIN EN 1706 

standards allow a very wide range of 

major alloying elements – silicon from 

10.5 to 13.5 %. The practical range for 

the silicon content is from 12.5 to 13.5 

and, in a slightly hypoeutectic range of 

10.5 to 11.2 %. However, these two alloys 

display entirely different solidifi cation 

behaviour. The intermediate range, with 

approx. 11.5 to 12.5 % silicon, runs the 

risk of shrinkage cavities. Casting alloys 

in this critical range are not offered. Even 

a blend of these different yet similarsounding 

alloys is not recommended.

Near-eutectic 

wheel casting alloys 


Alloy 



Silumin-Kappa Sr min 10.5 0.05 

max 11.0 0.15 0.02 0.10 0.25 0.07 0.15 0.03 0.10 Sr 

Silumin-Beta Sr min 9.0 0.20 

max 10.5 0.15 0.02 0.10 0.45 0.07 0.15 0.03 0.10 Sr 


max 11.8 0.15 0.03 0.10 0.45 0.07 0.15 0.03 0.10 Sr 

(0.19) (0.05) 

44000 





crack 

stability 


Silumin-Kappa Sr 

Silumin-Beta Sr 

Al Si11 






293 K - 373 K 


Silumin-Kappa Sr 2.68 74,000 0.91 600 - 555 21 20 - 26 150 - 180 

Silumin-Beta Sr 2.68 74,000 0.91 600 - 550 21 20 - 26 150 - 180 

Al Si11 2.68 74,000 0.91 600 - 550 21 18 - 24 140 - 170 


Near-eutectic wheel casting alloys 



hardness HB 

Fatigue 

resistance 

MPa MPa % MPa 


Silumin-Kappa Sr F Gravity die casting 170 80 6 45 60 - 90 

Silumin-Beta Sr F Gravity die casting 170 90 5 50 60 - 90 

T6 Gravity die casting 290 210 4 90 60 - 90 


Al Si11 F Gravity die casting 170 80 7 45 60 - 90 




Alloy / Temper Solution heat Annealing time Water Ageing Ageing time 

treatment temperature tempetarure 

temperature for quenching 

°C h °C °C h 

Silumin-Kappa Sr T4 520 - 535 4 - 10 20 160 - 170 6 - 8 

Silumin-Beta Sr T4 520 - 535 4 - 10 20 150 - 160 2 - 3 



MPa MPa % 

64 



Silumin-Kappa Sr F 180 170 160 120 90 80 70 50 5 6 6 10 65 45 45 40 

Silumin-Beta Sr T64 260 250 210 120 200 180 170 80 4,5 6 7 10 85 80 75 60 

Al Si11 F 230 170 160 130 130 80 70 50 3 7 7 10 65 45 40 35 






°C °C °C % % % 

Silumin-Kappa Sr 670 - 740 670 - 740 1.0 - 1.2 0.5 - 0.8 

Silumin-Beta Sr 670 - 740 670 - 740 1.0 - 1.2 0.5 - 0.8 

Al Si11 670 - 740 670 - 740 1.0 - 1.2 0.5 - 0.8


These casting alloy types have been 

developed primarily for the casting of 

car wheels by means of low-pressure 

die casting processes. 


These casting alloys have good fl uidity; 

the grain structure displays very high 

ductility and good corrosion resistance. 

The casting alloy Silumin-Kappa has an 

optimum silicon content of 10.5 to 11.0 %. 

In Silumin-Beta, the silicon content ranges 

from 9.0 and 10.5 % silicon. As a rule, 

these casting alloys already undergo a 

long-lasting strontium modifi cation (HV) 

during production of the ingots. The 

strontium addition is approx. 0.020 to 

0.030 %. Normally, this smelter modifi - 

cation does not need to be repeated at 

the foundry. The modifi cation of eutectic 

silicon, i.e. the formation of a modifi ed 

microstructure, is a necessity since the 

ductility of the cast structure of the wheels 

produced from these casting alloys meas- 

ured by means of the elongation value, 

for example, plays a vital role. The level 

of the iron content and the level of the 

other additions are particularly important 

quantities for the ductility or elongation 

of the cast structure. On request, these 

casting alloys can have a magnesium 

content of between 0.05 and 0.45 %. 

With an increasing Mg content, the alloys‘ 

strength can be improved slightly, 

their elongation decreases a little with the 

level of the Mg content, their machinability 

– with respect to chip formation, chip 

removal and surface appearance – is 

improved, the resistance of the casting 

to chemical attack increases, lacquer 

adherence, however, can be impaired 

by the magnesium content. Only some 

of the Silumin-Beta casting alloys are 

age-hardenable. The age hardening of 

wheels made from alloys of the Silumin- 

Kappa type is not recommended. It could 

cause partial embrittlement which would 

reduce the fatigue strength of the material. 

For wheels which have to be heat-treated, 

casting alloys of the Al Si7Mg (Pantal 7) 

type are recommended. The solidifi cation 

characteristics of these casting alloys 

are hypoeutectic. During solidifi cation, 

the transition is from pasty to mushy. 

In the course of subsequent solidifi cation, 

aluminium dendrites grow into the 

liquid melt. They form an interconnecting 

network whose intervening spaces 

are then fi lled with the highly-fl uid AlSi 

eutectic which then solidifi es. If feeding 

is incomplete or the highly-fl uid eutectic 

is drawn to another place, defects such 

as sinks or microporosity occur. The so- 

lidifi cation range is approx. 30 to 45 K. 

With this type of casting alloy, cleaning 

the melt can only be effected by means 

of inert gas or using a vacuum. Cleaning 

agents containing chlorine would remove 

strontium from the melt. In practice, the 

use of purging lances or impeller equipment 

have proven their worth. 


The 10 per cent aluminium-silicon 



Alloy 



VDS-No. 


Silumin-Beta / Al Si9Mg min 9.0 0.30 

(0.25) 

max 10.0 0.15 0.03 0.10 0.45 

(0.19) (0.05) (0.45) 0.07 0.15 0.03 0.10 Na 

43300 

Al Si10Mg(a) min 9.0 0.25 

(0.20) 

max 11.0 0.40 0.03 0.45 0.45 0.05 0.10 0.05 0.05 0.15 0.05 0.15 Na 

(0.55) (0.05) (0.45) 

43000 / 239 

Al Si10Mg(b) min 9.0 0.25 

(0.20) 

max 11.0 0.45 0.08 0.45 0.45 0.05 0.10 0.05 0.05 0.15 0.05 0.15 

(0.55) (0.10) (0.45) 

43100 

Al Si10Mg(Fe) min 9.0 0.45 0.25 

(0.20) 

max 11.0 0.9 0.08 0.55 0.50 0.15 0.15 0.15 0.05 0.15 0.05 0.15 

(1.0) (0.10) (0.50) (0.20) 

43400 / 239D 

Al Si10Mg(Cu) min 9.0 0.25 

(0.20) 

max 11.0 0.55 0.30 0.55 0.45 0.15 0.35 0.10 0.15 0.05 0.15 

(0.65) (0.35) (0.45) (0.20) 

43200 / 233 


max 11.0 0.55 0.08 0.50 0.10 0.05 0.15 0.05 0.05 0.15 0.05 0.15 

(0.65) (0.10) 

44400 

Silumin-Delta min 9.0 0.3 0.3 

max 10.5 0.4 0.02 0.4 0.03 0.07 0.15 0.03 0.10 

Silumin-Gamma min 9.0 0.4 0.15 

max 11.3 0.15 0.02 0.9 0.6 0.10 0.15 0.03 0.10 Sr 

Al Si10MnMg min 9.0 0.40 0.15 

(0.10) 

max 11.5 0.20 0.03 0.80 0.60 0.07 0.15 0.05 0.15 Sr 

(0.25) (0.05) (0.60) (0.20) 

43500 



66 




crack tightness state resistance anodisation 

stability 

Silumin-Beta / Al Si9Mg 

Al Si10Mg(a) 

Al Si10Mg(b) 

Al Si10Mg(Fe) 

Al Si10Mg(Cu) 

Al Si9 

Silumin-Delta 

Silumin-Gamma 

Al Si10MnMg 






293 K - 373 K 


Silumin-Beta / Al Si9Mg 2.68 74,000 0.91 600 - 555 21 20 - 26 150 - 180 

Al Si10Mg(a) 2.68 74,000 0.91 600 - 550 21 19 - 25 150 - 170 

Al Si10Mg(b) 2.68 74,000 0.91 600 - 550 21 18 - 25 140 - 170 

Al Si10Mg(Fe) 2.68 74,000 0.91 600 - 550 21 16 - 21 130 - 150 

Al Si10Mg(Cu) 2.68 74,000 0.91 600 - 550 21 16 - 24 130 - 170 

Al Si9 2.69 74,000 0.91 605 - 570 21 16 - 22 130 - 150 

Silumin-Delta 2.69 74,000 0.91 605 - 570 21 18 - 26 130 - 170 

Silumin-Gamma 2.68 74,000 0.91 610 - 560 21 20 - 26 140 - 180 

Al Si10MnMg 21 19 - 25 140 - 170 





hardness HB 

Fatigue 

resistance 

MPa MPa % MPa 


Silumin-Beta / Al Si9Mg F Sand casting 150 80 2 50 

T6 Sand casting 230 190 2 75 

Al Si10Mg(a) F Sand casting 150 80 2 50 


Al Si10Mg(b) F Sand casting 150 80 2 50 


Al Si10Mg(Cu) F Sand casting 160 80 1 50 


Silumin-Beta / Al Si9Mg T6 Gravity die casting 290 210 4 90 80 - 110 


Al Si10Mg(a) F Gravity die casting 180 90 2.5 55 80 - 110 


T64 Gravity die casting 240 200 2 80 

Al Si10Mg(b) F Gravity die casting 180 90 2.5 55 80 - 110 



Al Si10Mg(Cu) F Gravity die casting 180 90 1 55 80 - 110 


Al Si10Mg(Fe) F Pressure die casting 240 140 1 70 60 - 90 

Al Si9 F Pressure die casting 220 120 2 55 60 - 90 

Silumin-Delta F Pressure die casting 220 120 4 55 60 - 90 

Silumin-Gamma F Pressure die casting 240 120 5 70 80 - 90 

T6 Pressure die casting 290 210 7 100 



68 






°C h °C °C h 

Silumin-Beta / Al Si9Mg T6 520 - 535 4 - 10 20 160 - 170 6 - 8 

T64 520 - 535 4 - 10 20 150 - 160 2 - 3 

Al Si10Mg(a) T6 520 - 535 4 - 10 20 160 - 170 6 - 8 

T64 520 - 535 4 - 10 20 150 - 160 2 - 3 

Al Si10Mg(b) T6 520 - 535 4 - 10 20 160 - 170 6 - 8 

T64 520 - 535 4 - 10 20 150 - 160 2 - 3 

Al Si10Mg(Cu) T6 520 - 535 4 - 10 20 160 - 170 6 - 8 

Silumin-Gamma T6 500 - 530 4 - 8 20 150 - 170 2 - 6 

T64 500 - 530 4 - 8 20 180 - 340 2 - 6 



MPa MPa % 



Silumin-Beta / Al Si9Mg T6 290 290 260 120 220 210 200 80 3.5 4 4 10 90 90 80 60 

Al Si10Mg(a) T6 280 260 230 120 220 220 170 80 1 1 2 8 85 90 80 60 

Al Si10Mg(Cu) T6 280 240 210 120 220 200 180 90 1 1 2 7 85 80 75 45 





°C °C °C % % % 

Silumin-Beta / Al Si9Mg 670 - 740 670 - 740 1.0 - 1.2 0.5 - 0.8 

Al Si10Mg(a) 670 - 740 670 - 740 1.0 - 1.2 0.5 - 0.8 

Al Si10Mg(b) 670 - 740 670 - 740 1.0 - 1.2 0.5 - 0.8 

Al Si10Mg(Fe) 620 - 660 0.4 - 0.6 

Al Si10Mg(Cu) 670 - 740 670 - 740 1.0 - 1.2 0.5 - 0.8 

Al Si9 660 - 740 660 - 740 620 - 700 0.5 - 0.8 0.4 - 0.6 

Silumin-Delta 620 - 700 0.4 - 0.6 

Silumin-Gamma 620 - 730 0.4 - 0.6 




This important group of casting alloys 

is used for castings with medium wall 

thicknesses which require higher, to the 

highest strength properties. The fi elds of 

application comprise mechanical and 

electrical engineering, the food industry 

as well as in engine and motor vehicle 

construction. Silumin-Beta casting alloys 

are also used for car wheels. Silumin- 

Gamma is a heat-treatable high-pressure 

die casting alloy. However, successful 

treatment requires the use of an adequate 

casting process (e.g. vacuum-assisted 

high-pressure die casting). 

70 



The fl uidities of these casting alloys are 

still good. Heat-treatable castings made 

from alloys containing magnesium dis- 

play particularly good machinability. With 

increasing purity, the ductility of the cast 

structure also increases. Where the requirements 

on corrosion resistance are 

high, high-purity grades are selected. 

Sand and gravity die castings can be 

artifi cially aged. In doing so, however, 

ductility decreases. The solidifi cation 

characteristics of this group of casting 

alloys are hypoeutectic. During the solidifi 

cation process, aluminium dendrites 

grow into the melt fi rst. The highly-fl uid 

AlSi eutectic then penetrates the intervening 

spaces of the network and clamps 

the microstructural framework together. 

If the feeding of the remaining eutectic 

melt is hindered in any way, defects such 

as sinks or micro/macrocavities occur. 

This causes porous areas and also leads 

to a weakening of the structural crosssection. 

During casting, therefore, attention 

must be paid to ensure good feeding 

and, as far as possible, controlled 

solidifi cation. The solidifi cation range 

amounts to approx. 45 K. 

Where requirements on elongation or 

ductility are higher, modifi cation of the 

melt is recommended. The casting alloys 

for use in gravity die casting are modifi 

ed with sodium or strontium. For sand 

casting, modifi cation with sodium only 

is recommended. As a general rule, the 

casting alloys for sand and gravity die 

casting are offered in versions which can 

be easily modifi ed.

The 7 and 5 per cent aluminium-silicon 



Alloy 



VDS-No. 


Pantal 7 / Al Si7Mg0.3 min 6.5 0.30 

(0.25) 

max 7.5 0.15 0.03 0.10 0.45 0.07 0.18 0.03 0.10 Na / Sr 

(0.19) (0.05) (0.45) (0.25) 

42100 

Al Si7Mg0.6 min 6.5 0.50 

(0.45) 

max 7.5 0.15 0.03 0.10 0.70 0.07 0.18 0.03 0.10 

(0.19) (0.05) (0.70) (0.25) 

42200 

Al Si7Mg min 6.5 0.25 

(0.20) 

max 7.5 0.45 0.15 0.35 0.65 0.15 0.15 0.15 0.05 0.20 0.05 0.15 

(0.55) (0.20) (0.65) (0.25) 

42000 

Pantal 5 min 5.0 0.40 0.05 

max 6.0 0.15 0.02 0.10 0.80 0.07 0.20 0.03 0.10 

Al Si5Mg min 5.0 0.40 0.05 

max 6.0 0.3 0.03 0.4 0.80 0.10 0.20 0.05 0.15 

- / 235 

Al Si5Cu1Mg min 4.5 1.0 0.40 

(0.35) 

max 5.5 0.55 1.5 0.55 0.65 0.25 0.15 0.15 0.05 0.20 0.05 0.15 

(0.65) (0.65) (0.25) 

45300 

Al Si7Cu0.5Mg min 6.5 0.2 0.25 

(0.20) 

max 7.5 0.25 0.7 0.15 0.45 

(0.45) 

0.07 0.20 0.03 0.10 

45500 




The 7 and 5 per cent aluminium-silicon casting alloys 




stability 

Pantal 7 / Al Si7Mg0.3 

Al Si7Mg0.6 

Al Si7Mg 

Pantal 5 

Al Si5Mg 

Al Si5Cu1Mg 

Al Si7Cu0.5Mg 






293 K - 373 K 


Pantal 7 / Al Si7Mg0.3 2.66 73,000 0.92 625 - 550 22 21 - 27 160 - 180 

Al Si7Mg0.6 2.66 73,000 0.92 625 - 550 22 20 - 26 150 - 180 

Al Si7Mg 2.66 73,000 0.92 625 - 550 22 19 - 25 150 - 170 

Pantal 5 2.67 72,000 0.92 625 - 550 23 21 - 29 150 - 180 

Al Si5Mg 2.67 72,000 0.92 625 - 550 23 21 - 26 150 - 180 

Al Si5Cu1Mg 2.67 72,000 0.92 625 - 550 22 19 - 23 140 - 150 

Al Si7Cu0.5Mg 22 16 - 22 150 - 165 

72 




hardness HB 

Fatigue 

resistance 

MPa MPa % MPa 


Pantal 7 / Al Si7Mg0.3 T6 Sand casting 230 190 2 75 

Al Si7Mg0.6 T6 Sand casting 250 210 1 85 

Al Si7Mg F Sand casting 140 80 2 50 


Pantal 5 T6 Sand casting 240 220 2 80 


Al Si5Mg T6 Sand casting 240 220 1 80 


Al Si5Cu1Mg T6 Sand casting 230 200

The 7 and 5 per cent aluminium-silicon casting alloys 





°C h °C °C h 

Pantal 5 T4 520 - 535 4 - 10 20 20 - 30 120 

T6 520 - 535 4 - 10 155 - 165 6 - 10 

Al Si5Mg T4 520 - 535 4 - 10 20 20 - 30 120 

T6 520 - 535 4 - 10 155 - 165 6 - 10 

Al Si5Cu1Mg T4 520 - 535 4 - 10 20 20 - 30 120 

T6 520 - 535 4 - 10 155 - 165 6 - 10 

Pantal 7 / Al Si7Mg0.3 T6 520 - 545 4 - 10 155 - 165 6 - 10 

T64 520 - 545 4 - 10 20 150 - 160 2 - 5 

Al Si7Mg0,6 T6 520 - 545 4 - 10 155 - 165 6 - 10 

T64 520 - 545 4 - 10 20 150 - 160 2 - 5 

Al Si7Mg T6 520 - 545 4 - 10 155 - 165 6 - 10 

T64 520 - 545 4 - 10 20 150 - 160 2 - 5 



MPa MPa % 

74 



Pantal 7 / Al Si7Mg0.3 T6 290 290 240 120 210 210 180 80 3 4 6 10 90 90 75 45 

Pantal 5 T6 280 260 200 120 250 240 170 80 1 2 3 7 90 90 80 45 

Al Si5Mg T6 280 260 200 120 250 240 170 80 0.5 1 2 7 90 90 80 45 






°C °C °C % % % 

Pantal 7 / Al Si7Mg0.3 680 - 750 680 - 750 1.0 - 1.2 0.7 - 1.1 

Al Si7Mg0.6 680 - 750 680 - 750 1.0 - 1.2 0.7 - 1.1 

Al Si7Mg 680 - 750 680 - 750 1.0 - 1.2 0.7 - 1.1 

Pantal 5 690 - 760 690 - 760 1.1 - 1.2 0.8 - 1.1 

Al Si5Mg 690 - 760 690 - 760 1.1 - 1.2 0.8 - 1.1 

Al Si5Cu1Mg 690 - 760 690 - 760 1.0 - 1.2 0.8 - 1.1


These casting alloys are used in the 

motor vehicle industry (chassis components, 

motor car and lorry wheels), for 

components in the aerospace industry, 

for parts in mechanical engineering, for 

hydraulic elements, in the food industry, 

in shipbuilding, for fi ttings and apparatus 

as well as for fi re extinguisher compo- 

nents. Their use makes particular sense 

when the castings undergo age harden- 

ing. As a result of age hardening, these 

casting alloys are used in structures 

requiring high strength. In addition, the 

cast structure – particularly of primary 

casting alloys – still displays remarkable 

toughness and ductility. Resistance to 

chemical attack increases with purity 

and is very good in the case of primary 



Owing to the low silicon content, fl uidity 

is only moderate. Castings with very 

thin walls can not, therefore, be cast in 

these alloys. This group of casting alloys 

containing around 7 % silicon is in 

some respects an exception. Looking 

at a micrograph, it can be seen that the 

proportion by area of light matrix (i.e. 

the aluminium-rich solid solution) and 

the proportion by area or eutectic silicon 

(i.e. the dotted grey areas) each amount 

to approx. 50 %. Like in all hypoeutectic 

AlSi casting alloys, solidifi cation takes 

place in phases. First of all, the dendritic 

network made up of aluminium-rich solid 

solution grows into the still liquid melt. 

The remaining highly-fl uid eutectic melt 

infi ltrates this sponge and locks the struc- 

ture together like in a two-component 

composite. By means of age-harden- 

ing, the aluminium-rich solid solution 

in particular is strengthened while the 

connecting eutectic remains ductile. In 

this way, the ideal microstructure occurs, 

giving the highest possible strength with 

still acceptable elongation. The variable 

magnesium content which ranges from 

0.20 to 0.70 % gives the user the possibility 

of adjusting the elongation of the 

castings to the particular requirements. 

With a low magnesium content of around 

0.25 %, relatively high elongation values 

can be achieved. Where greater hardness 

is required, casting alloys with a magnesium 

content of 0.70 % can be used. 

The group of casting alloys with approx. 

5 % silicon displays many sequences 

and properties which are similar to the 

7 per cent group. The solidifi cation range 

is slightly greater, fl uidity is slightly less. 

Due to the lower silicon content, the effect 

of the aluminium-rich solid solution 

dominates. The casting alloy variants 

with low copper content display the best 

possible corrosion-resistance behaviour 

of all aluminium-silicon casting alloys. 

Castings made from these alloys fi nd 

application in such areas as the food 

industry, in domestic appliances or in 

parts for the food processing industry. 




Alloy 



VDS-No. 


Al Si8Cu3 min 7.5 2.0 0.15 0.15 

(0.05) 

max 9.5 0.7 3.5 0.65 0.55 0.35 1.2 0.25 0.15 0.20 0.05 0.25 

(0.8) (0.55) (0.25) 

46200 / 226 

Al Si9Cu3(Fe) min 8.0 0.6 2.0 0.15 

(0.05) 

max 11.0 1.1 4.0 0.55 0.55 0.15 0.55 1.2 0.35 0.15 0.20 0.05 0.25 

(1.3) (0.55) (0.25) 

46000 / 226D 

Al Si11Cu2(Fe) min 10.0 0.45 1.5 

max 12.0 1.0 2.5 0.55 0.30 0.15 0.45 1.7 0.25 0.15 0.20 0.05 0.25 

(1.1) (0.25) 

46100 

Al Si7Cu3Mg min 6.5 3.0 0.20 0.35 

(0.30) 

max 8.0 0.7 4.0 0.65 0.60 0.30 0.65 0.15 0.10 0.20 0.05 0.25 

(0.8) (0.60) (0.25) 

46300 

Al Si9Cu1Mg min 8.3 0.8 0.15 0.30 

(0.25) 

max 9.7 0.7 1.3 0.55 0.65 0.20 0.8 0.10 0.10 0.18 0.05 0.25 

(0.8) (0.65) (0.20) 

46400 

Al Si9Cu3(Fe)(Zn) min 8.0 0.6 2.0 0.15 

(0.05) 

max 11.0 1.2 4.0 0.55 0.55 0.15 0.55 3.0 0.35 0.15 0.20 0.05 0.25 

(1.3) (0.55) (0.25) 

46500 / 226/3 

Al Si7Cu2 min 6.0 1.5 0.15 

max 8.0 0.7 2.5 0.65 0.35 0.35 1.0 0.25 0.15 0.20 0.05 0.15 

(0.8) (0.25) 

46600 

Al Si6Cu4 min 5.0 3.0 0.20 

max 7.0 0.9 5.0 0.65 0.55 0.15 0.45 2.0 0.30 0.15 0.20 0.05 0.35 

(1.0) (0.25) 

45000 / 225 

Al Si5Cu3Mg min 4.5 2.6 0.20 

(0.15) 

max 6.0 0.50 3.6 0.55 0.45 0.10 0.20 0.10 0.05 0.20 0.05 0.15 

(0.60) (0.45) (0.25) 

45100 

Al Si5Cu3 min 4.5 2.6 

max 6.0 0.50 3.6 0.55 0.05 0.10 0.20 0.10 0.05 0.20 0.05 0.15 

(0.60) (0.25) 

45400 



76 





stability 

Al Si8Cu3 

Al Si9Cu3(Fe) 

Al Si11Cu2(Fe) 

Al Si7Cu3Mg 

Al Si9Cu1Mg 

Al Si9Cu3(Fe)(Zn) 

Al Si7Cu2 

Al Si6Cu4 

Al Si5Cu3Mg 

Al Si5Cu3 






293 K - 373 K 


Al Si8Cu3 2.77 75,000 0.88 600 - 500 21 14 - 18 110 - 130 

Al Si9Cu3(Fe) 2.76 75,000 0.88 600 - 500 21 13 - 17 110 - 120 

Al Si11Cu2(Fe) 2.75 75,000 0.88 600 - 500 20 14 - 18 120 - 130 

Al Si7Cu3Mg 2.77 75,000 0.88 600 - 500 21 14 - 17 110 - 120 

Al Si9Cu1Mg 2.76 75,000 0.88 600 - 500 21 16 - 22 130 - 150 

Al Si9Cu3(Fe)(Zn) 2.76 75,000 0.88 600 - 500 21 13 - 17 110 - 120 

Al Si7Cu2 2.77 75,000 0.88 600 - 500 21 15 - 19 120 - 130 

Al Si6Cu4 2.80 74,000 0.88 630 - 500 22 14 - 17 110 - 120 

Al Si5Cu3Mg 2.79 74,000 0.88 630 - 500 22 16 - 19 130 

Al Si5Cu3 2.79 74,000 0.88 630 - 500 22 16 - 19 120 - 130 





hardness HB 

Fatigue 

resistance 

MPa MPa % MPa 


Al Si8Cu3 F Sand casting 150 90 1 60 

Al Si7Cu3Mg F Sand casting 180 100 1 80 

Al Si9Cu1Mg F Sand casting 135 90 1 60 



Al Si5Cu3Mg T4 Sand casting 140 70 1 60 

T6 Sand casting 230 200





°C h °C °C h 

Al Si5Cu3Mg T4 480 6 - 10 20 - 60 20 - 30 120 

T6 480 6 - 10 20 160 6 - 12 

Al Si5Cu3 T4 480 6 - 10 20 - 60 20 - 30 120 

Al Si9Cu1Mg T6 480 6 - 10 20 160 6 - 12 



MPa MPa % 


Al Si8Cu3 F 170 160 120 80 100 90 50 25 1 1 2 5 75 65 45 35 

Al Si6Cu4 F 170 160 130 100 100 90 60 30 1 1 1.5 4 75 65 50 40 






°C °C °C % % % 

Al Si8Cu3 680 - 750 680 - 750 630 - 680 1.0 - 1.2 0.6 - 1.0 0.4 - 0.6 

Al Si9Cu3(Fe) 630 - 680 0.4 - 0.7 

Al Si11Cu2(Fe) 630 - 680 0.4 - 0.8 

Al Si7Cu3Mg 680 - 750 680 - 750 1.0 - 1.2 0.6 - 1.0 

Al Si9Cu1Mg 680 - 750 680 - 750 1.0 - 1.2 0.6 - 1.0 

Al Si9Cu3(Fe)(Zn) 630 - 680 0.4 - 0.7 

Al Si7Cu2 680 - 750 680 - 750 1.0 - 1.2 0.6 - 1.0 

Al Si6Cu4 690 - 750 690 - 750 640 - 690 1.0 - 1.2 0.6 - 1.0 0.4 - 0.6 

Al Si5Cu3Mg 690 - 750 690 - 750 1.0 - 1.2 0.6 - 1.0 

Al Si5Cu3 690 - 750 690 - 750 1.0 - 1.2 0.6 - 1.0 




The alloys in this group are among the 

most commonly used aluminium casting 

alloys around. They are regarded 

as universal casting alloys for the most 

important casting processes and are 

widely used in pressure die casting in 

particular. They are easily cast and are 

suitable for parts which are subjected 

to relatively high loads. They are heat 

resistant and, as such, are used for engine 

components and cylinder heads. 

80 



Aluminium casting alloys with approx. 6 

to 8 % silicon, 3 to 4 % copper as well 

as 0.3 to 0.5 % magnesium have the 

optimum high-temperature strength. 

The cast structure hardens on its own 

within a week of casting. Afterwards, the 

mechanical machinability of the casting 

is very good. Age hardening is some- 

times possible. Treatment of the melt: 

In sand castings or thick-walled grav- 

ity die castings, sodium modifi cation is 

possible. Often, grain refi nement is also 

carried out. The casting and solidifi ca- 

tion behaviour usually poses no problem. 

The type of solidifi cation is hypoeutectic. 

During the transition from liquid to 

solid state, there is a wide solidifi cation 

range of a pasty-mushy character. Attention 

must be paid to controlling the 

solidifi cation and feeding of the metal. 

There is no distinctive tendency to hot 

cracking or draws. 


With castings made from these casting 

alloys, age hardening is possible when 

the Cu and Mg content is appropriate. It 

is, however, seldom carried out. In these 

castings, due to the Cu content in connection 

with the Mg and Zn content, an 

independent structural hardening occurs. 

This process is complete within about a 

week. Only then should the castings be 

fi nished followed by checking the mechanical 

properties. To achieve thermal 

and dimensional stability in parts suitable 

for high-pressure applications, e.g. 

crankcases, cylinder heads or pistons, 

solution annealing with artifi cial ageing 

beyond the peak aged condition is sug- 

gested (T7). This process is also known 

as “stabilising” or “overageing”.



Alloy 



VDS-No. 


Al Mg3(H) min 2.7 

max 0.45 0.15 0.02 0.40 3.2 0.07 0.02 0.03 0.10 B/Be 


(2.5) 

max 0.45 0.40 0.03 0.45 3.5 0.10 0.15 0.05 0.15 B/Be 

(0.55) (0.55) (0.05) (3.5) (0.20) 

51100 / 242 

Al Mg3(Cu) min 2.5 

max 0.60 0.55 0.15 0.45 3.2 0.30 0.20 0.05 0.15 B/Be 

- / 241 

Al Mg3Si(H) min 0.9 2.7 

max 1.3 0.15 0.02 0.40 3.2 0.07 0.15 0.03 0.10 B/Be 


(4.5) 

max 0.35 0.45 0.05 0.45 6.5 0.10 0.15 0.05 0.15 B/Be 

(0.55) (0.55) (0.10) (6.5) (0.20) 

51300 / 244 

Al Mg5(Si) min 4.8 

(4.5) 

max 1.3 0.45 0.03 0.45 6.5 0.10 0.15 0.05 0.15 B/Be 

(1.5) (0.55) (0.05) (6.5) (0.20) 

51400 / 245 

Al Mg9(H) min 1.7 0.2 8.5 

max 2.5 0.50 0.02 0.5 10.5 0.07 0.15 0.03 0.10 B/Be 

Al Mg9 min 0.45 8.5 

(8.0) 

max 2.5 0.9 0.08 0.55 10.5 0.10 0.25 0.10 0.10 0.15 0.05 0.15 B/Be 

(1.0) (0.10) (10.5) (0.20) 

51200 / 349 

Al Mg5Si2Mn min 1.8 0.4 5.0 

(4.7) 

max 2.6 0.20 0.03 0.8 6.0 0.07 0.20 0.05 0.15 

(0.25) (0.05) (6.0) (0.25) 

51500 

Al Si2MgTi min 1.6 0.30 0.50 0.07 

(0.45) (0.05) 

max 2.4 0.50 0.08 0.50 0.65 0.05 0.10 0.05 0.05 0.15 0.05 0.15 

(0.60) (0.10) (0.65) (0.20) 

41000 







Al Mg3(H) 

Al Mg3 

Al Mg3(Cu) 

Al Mg3Si(H) 

Al Mg5 

Al Mg5(Si) 

Al Mg9(H)/Fe 

Al Mg9 

Al Mg3(Zr) 

Al Mg5Si2Mn 

Al Si2MgTi 

crack 

stability 







293 K - 373 K 


Al Mg3(H) 2.68 70,000 0.93 650 - 600 24 17 - 22 130 - 140 

Al Mg3 2.68 70,000 0.93 650 - 600 24 17 - 22 130 - 140 

Al Mg3(Cu) 2.68 70,000 0.93 650 - 600 24 17 - 22 130 - 140 

Al Mg3Si(H) 2.68 70,000 0.93 650 - 600 24 17 - 22 130 - 140 

Al Mg5 2.66 69,000 0.94 630 - 550 24 15 - 21 110 - 130 

Al Mg5(Si) 2.66 69,000 0.94 630 - 550 24 15 - 21 110 - 140 

Al Mg9(H)/Fe 2.63 68,000 0.94 620 - 520 24 11 - 14 60 - 90 

Al Mg9 2.63 68,000 0.94 620 - 520 24 11 - 14 60 - 90 

Al Mg5Si2Mn 24 14 - 16 110 - 130 

Al Si2MgTi 23 19 - 25 140 - 160 

82 




hardness HB 

Fatigue 

resistance 

MPa MPa % MPa 


Al Mg3(H) F Sand casting 140 70 5 50 

Al Mg3 F Sand casting 140 70 3 50 

Al Mg3(Cu) F Sand casting 140 70 2 50 

Al Mg3Si(H) F Sand casting 140 70 3 50 

Al Mg5 F Sand casting 16 90 3 55 

Al Si2MgTi F Sand casting 140 70 3 50 


Al Mg5(Si) F Sand casting 160 100 3 60 

Al Mg3(H) F Gravity die casting 150 70 5 50 60 - 90 

Al Mg3 F Gravity die casting 150 70 5 50 60 - 90 

Al Mg3(Cu) F Gravity die casting 150 70 3 50 60 - 90 

Al Mg3Si(H) F Gravity die casting 150 70 3 50 70 - 80 


Al Mg5 F Gravity die casting 180 100 4 60 60 - 90 

Al Si2MgTi F Gravity die casting 140 70 3 50 


Al Mg5(Si) F Gravity die casting 180 110 3 65 60 - 90 


Al Mg3 F 140 70 3 50 

Al Mg5 F 160 90 3 55 

Al Mg5(Si) F 180 110 3 65 

Al Mg9(H)/Fe F Pressure die casting 200 140 1 70 60 - 90 

Al Mg9 F Pressure die casting 200 130 1 70 60 - 90 

Al Si2MgTi F Gravity die casting 170 70 5 50 

Al Si2MgTi T6 Gravity die casting 260 180 5 85 







°C h °C °C h 

Al Mg3Si(H) T6 545 - 555 4 - 10 20 160 - 170 8 - 10 

Al Mg5(Si) T6 540 - 550 4 - 10 20 160 - 170 8 - 10 

Al Si2MgTi T6 520 - 535 4 - 10 20 155 - 165 7 - 10 





MPa MPa % 

84 



Al Mg3Si(H) T6 220 210 120 80 150 140 60 30 4 4 5 14 75 45 40 20 

Al Mg5(Si) T6 210 200 170 140 120 110 100 70 4 4 5 8 70 70 60 30 






°C °C °C % % % 

Al Mg3(H) 700 - 750 700 - 750 1.0 - 1.5 0.7 - 1.2 

Al Mg3 700 - 750 700 - 750 1.0 - 1.5 0.7 - 1.2 

Al Mg3(Cu) 700 - 750 700 - 750 1.0 - 1.5 0.7 - 1.2 

Al Mg3Si(H) 700 - 750 700 - 750 1.0 - 1.5 0.7 - 1.2 

Al Mg5 700 - 750 700 - 750 1.0 - 1.5 0.7 - 1.2 

Al Mg5(Si) 700 - 750 700 - 750 1.0 - 1.5 0.7 - 1.2 

Al Mg9(H)/Fe 680 - 640 0.5 - 0.7 

Al Mg9 680 - 640 0.5 - 0.7


We produce Al Mg3-type casting alloys 

for handles, window handles or security 

covers in decorative anodised quality. 

For structures in the chemical industry, in 

shipbuilding or the food industry, which 

demand the highest possible resistance 

to chemical attack and the infl uences of 

maritime climates, Al Mg5-type cast- 

ing alloys are suitable. Heat-resistant 

Al Mg5Si-type casting alloys are suit- 

able for high-temperature applications 

such as engine construction. In France, 

the Al Si2MgTi alloy is used for handles. 

For pressure die castings with good corrosion 

resistance, Al Mg9-type casting 

alloys are used. 


The highest requirements are placed on 

the quality of these casting alloys – particularly 

for decorative parts which are 

anodised. The manufacture of these casting 

alloys represents a special challenge 

for smelters requiring much experience, 

the best raw materials and quality-oriented 

work. 

Notes about surface treatment 

As a pre-treatment, the surfaces of cast- 

ings made from Al Mg3, for example, are 

mechanically machined as well as often 

being chemically polished. In the anodis- 

ing process (electrolytically-oxidised alu- 

minium), a protective oxide layer, which 

grows inwards and is essentially more 

impervious, thicker, more wear resistant 

and more homogeneous than a natural 

oxide skin, is produced on the surface 

of a casting. On pure aluminium and on 

aluminium alloys which are low in precipitates, 

these layers are transparent. 

All defects such as precipitated intermetallic 

phases, inclusions, heterogeneities, 

oxide fi lms, wrinkles and other 

casting defects lead to disturbances in 

the growth of the layer formation and, 

consequently, impairment of the decorative 

appearance. 

As the electro-chemically formed oxide 

layer is also the possible carrier of discolouring 

substances, defects near the 

surface can lead to the parts having a 

blemished, non-decorative appearance. 

Hollow spaces such as wrinkles or pores 

which have been cut can be taken up 

by the aqueous solutions or electrolyte 

during treatment. Even later, due to a 

secondary reaction, the remainder of this 

medium can lead to local decomposition 

of the anodised or colour coating. 



The following alloying constituents can 

have an infl uence on the quality and ap- 

pearance of anodised layers: 

Silicon 

With Si concentrations higher than 

0.6 %, the precipitated silicon or Mg2Si 

impairs transparency. The anodised layer 

loses its brilliance. 

Iron, chromium and manganese 

The sum total of these elements can 

have a yellowing effect on the anodised 

layer. Limiting concentrations can not 

be established. Their infl uence depends 

on the phase composition and chemical 

back-dissolution during anodising. 

Copper 

It has no negative infl uence when found 

in normal concentrations. In the case of 

higher additions, the layer becomes softer 

and the composition rougher. 

Zinc 

This element has no infl uence on the 

anodising process or pigmentation. 

Titanium 

Concentrations of Ti above 0.02 % have 

a negative effect on the electrolytic colouration 

of aluminium castings. 

86 


Notes on casting techniques 

To avoid the tendency to hot tearing 

during casting and particularly for deco- 

rative reasons, the cast structure must 

be fi ne-grained. This fi ne-grained struc- 

ture can already be achieved during the 

production of the ingots by means of 

intensive grain refi nement. As a general 

rule, this grain refi nement does not have 

to be repeated during pouring. Should 

grain refi nement decrease as a result 

of prolonged holding, we recommend 

that it be freshened up using TiB grain 

refi ning wire. Melt cleaning or keeping 

the melt clean is important in order to 

produce a cast piece of good quality. 

We recommend that only those refi n- 

ing fl uxes which are specifi cally suited 

to AlMg casting alloys be used. 

Bale-out vessels with ceramic fi lter ele- 

ments have also proven their worth. Dur- 

ing casting, only the fi ltrate is baled out; 

the ladle remainder and subsequently 

charged metal enter into the outside 

areas of the melting or holding crucible. 

The casting operation requires particular 

care in order to produce a sound casting 

despite the constant risk of forming 

oxides and shrinkage. In doing this, the 

confi guration of the dies and the casting 

system play an important role. The 

type of solidifi cation is globular-mushy. 

A good feeding system is an essen- 

tial prerequisite for producing a dense 

structure.



Alloy 



VDS-No. 



Al Cu4Ti min 4.2 0.15 

(0.15) 

max 0.15 0.15 5.2 0.55 0.07 0.25 0.03 0.10 

(0.18) (0.19) (0.30) 

21100 

Al Cu4MgTI min 4.2 0.20 0.15 

(0.15) (0.15) 

max 0.15 0.30 5.0 0.10 0.35 0.05 0.10 0.05 0.05 0.25 0.03 0.10 

(0.20) (0.35) (0.35) (0.30) 

21000 

Al Cu4MnMg min 4.0 0.20 0.20 

(0.15) 

max 0.10 0.15 5.0 0.50 0.50 0.03 0.05 0.03 0.03 0.05 0.03 0.10 

(0.20) (0.50) (0.05) (0.10) (0.10) 

21200 

Al Cu4MgTiAg min 4.0 0.01 0.15 0.5 Ag 

0.4 

max 0.05 0.10 5.2 0.50 0.35 0.05 0.35 0.03 0.10 1.0 

Al Cu5NiCoSbZr min 4.5 0.1 1.3 0.15 **** 

max 0.20 0.30 5.2 0.3 0.10 1.7 0.10 0.30 0.05 0.15 


AlSi12CuNiMg min 10.5 0.8 0.9 

(0.8) 

0.7 

max 13.5 0.6 1.5 0.35 1.5 1.3 0.35 0.20 0.05 0.15 P 

(0.7) (1.5) (0.25) 

48000 / 260 

Al Si18CuNiMg min 17.0 0.8 0.8 0.8 

max 19.0 0.3 1.3 0.10 1.3 1.3 0.10 0.15 0.05 0.15 P 

****) Co 0.10-0.40 Sb 0.10-0.30 Zr 0.10-0.30 







Alloy 




Al Si17Cu4Mg* min 16.0 4.0 0.5 

max 18.0 0.3 5.0 0.15 0.65 0.10 0.10 0.20 0.05 0.15 P 

Al Si17Cu4Mg** min 16.0 4.0 0.45 

(0.25) 

max 18.0 1.0 5.0 0.50 0.65 0.3 1.5 0.15 0.20 0.05 0.25 

(1.3) (0.65) (0.25) 

48100 


Autodur min 8.5 0.3 9.5 

max 9.5 0.15 0.02 0.05 0.5 10.5 0.15 0.03 0.10 

Autodur (Fe)* min 8.5 0.3 9.5 

max 9.5 0.40 0.02 0.30 0.5 10.5 0.15 0.03 0.10 

Autodur (Fe)** min 7.5 0.25 

(0.20) 

9.0 

max 9.5 0.27 0.08 0.15 0.5 10.5 0.15 0.05 0.15 

(0.30) (0.10) (0.5) 

71100 


Al 99.7E*** min 

max 0.07 0.20 0.01 0.005 0.02 0.004 0.04 Mn+Cr+ 0.03 

V+ Ti= 

0.02 

B 0.04 

Al 99.6E*** min 

max 

*) Non-standardised version 

0.10 0.30 0.01 0.007 0.02 0.005 0.04 Mn+Cr+ 0.03 

V+Ti= 

0.030 

B 0.04 

**) According to DIN EN 1706: 2010 

***) According to DIN EN 576 



88 





stability 


Al Cu4Ti 

Al Cu4TiMgTi 

Al Cu4TiMgAg 

Al Cu5NiCoSbZr 


Al Si12CuNiMg 

Al Si18CuNiMg 


Al Si17Cu4Mg 1) 

Al Si17Cu4Mg 2) 


Autodur 

Autodur(Fe) 

Al Zn10Si8Mg 1) 


Al 99.7E 

Al 99.6E 

1) Non-standardised version 









293 K - 373 K 



Al Cu4Ti 2.79 72,000 0.91 640 - 550 23 16 - 23 120 - 150 

Al Cu4MgTi 2.79 72,000 0.91 640 - 550 23 16 - 23 120 - 150 

Al Cu4TiMgAg 2.79 72,000 0.91 640 - 550 23 16 - 23 120 - 150 

Al Cu5NiCoSbZr 2.84 76,000 0.91 650 - 550 23 18 - 24 120 - 155 


Al Si12CuNiMg 2.68 77,000 0.90 600 - 540 20 15 - 23 130 - 160 

Al Si18CuNiMg 2.68 81,000 0.90 680 - 520 19 14 - 18 115 - 140 


Al Si17Cu4Mg 1) 2.73 81,000 0.89 650 - 510 19 14 - 18 115 - 130 

Al Si17Cu4Mg 2) 18 14 - 17 120 - 130 


Autodur 2.85 75,000 0.86 640 - 550 21 15 - 20 115 - 150 

Autodur(Fe) 2.85 75,000 0.86 640 - 550 21 15 - 20 115 - 150 

Al Zn10Si8Mg 2) Rotor-Aluminium 

21 17 - 20 120 - 130 

Al 99.7E 2.70 70,000 0.94 660 24 34 - 36 180 - 210 

Al 99.6E 2.70 70,000 0.94 660 24 32 - 34 180 - 210 



90 




hardness HB 

Fatigue 

resistance 

MPa MPa % MPa 



Al Cu4Ti T6 Sand casting 300 200 3 95 


Al Cu4TiMg T4 Sand casting 300 200 5 90 

Al Cu4TiMgAg T6 Sand casting 460 - 510 410 - 450 7 130 - 150 

T64 Sand casting 370 - 430 200 - 270 14 - 18 105 - 120 

Al Cu5NiCoSbZr T7 Sand casting 180 - 220 145 - 165 1 - 1.5 85 - 95 90 - 100 

T5 Sand casting 180 - 220 160 - 180 1 - 1.5 80 - 90 90 - 100 

Al Cu4Ti(H) T6 Gravity die casting 330 220 7 95 80 - 110 


Al Cu4MgTi T4 Gravity die casting 320 200 8 95 80 - 110 

Al Cu4TiMgAg T6 Gravity die casting 460 - 510 410 - 460 8 130 - 150 100 - 110 


Al Si12CuNiMg F Sand casting 140 130 ≤1 80 

T6 Sand casting 220 190 ≤1 90 



Al Si17Cu4Mg F Sand casting 140 130 ≤1 80 


T5 Sand casting 230 220 ≤1 100 

Al Si18CuNiMg F Sand casting 140 130 ≤1 85 

T6 Sand casting 230 210 ≤1 100 


Al Si12CuNiMg F Gravity die casting 200 190 ≤1 90 80 - 110 

T6 Gravity die casting 280 240 ≤1 100 


Al Si17Cu4Mg F Gravity die casting 180 170 ≤1 100 80 - 110 



Al Si18CuNiMg F Gravity die casting 180 170 ≤1 90 80 - 110 








hardness HB 

Fatigue 

resistance 

MPa MPa % MPa 



Al Si12CuNiMg F Pressure die casting 240 140 ≤1 90 

T5 Pressure die casting 240 140 ≤1 90 

Al Si17Cu4Mg 1) F Pressure die casting 220 200 ≤1 100 

T5 Pressure die casting 230 210 ≤1 100 

Al Si18CuNiMg F Pressure die casting 210 180 ≤1 100 


Autodur T1 Sand casting 210 190 ≤1 90 

Al Zn10Si8Mg T1 Sand casting 210 190 1 90 

Autodur T1 Gravity die casting 260 210 ≤1 100 80 - 100 

Autodur(Fe) T1 Pressure die casting 290 230 ≤1 100 


Al 99.7E F Gravity die casting 60 20 30 14 

Al 99.6E F Gravity die casting 60 20 30 14 

Al 99.7E F Pressure die casting 80 20 10 15 

Al 99.6E 


F Pressure die casting 80 20 10 15 



92 






°C h °C °C h 


Al Cu4TiMg T4 520 - 530 8 - 16 20 - 80 15 - 30 > 120 

Al Cu5NiCoSbZr T5 Air 345 - 355 8 - 10 

T7 535 - 545 10 - 15 20 - 80 210 - 220 12 - 16 

Al Cu4Ti T6 515 - 535 8 - 18 20 - 80 170 - 180 6 - 8 

Al Cu4TiMgAg T6 525 - 535 8 - 18 20 - 80 170 - 180 6 - 7 

Al Cu4Ti(H) T64 515 - 535 8 - 18 20 - 80 135 - 145 6 - 8 


Al Si12CuNiMg T5 Air quenching None 210 - 230 10 - 14 

T6 520 - 530 5 - 10 20 - 80 165 - 185 5 - 10 

Al Si18CuNiMg T5 Air quenching None 225 - 235 7 - 12 

T6 495 - 505 7 - 10 20 - 80 165 - 185 7 - 10 

T7 


495 - 505 7 - 10 20 - 80 225 - 235 7 - 10 

Al Si17Cu4Mg 1) T5 Air quenching None 225 - 235 7 - 12 

T6 495 - 505 7 - 10 20 - 80 165 - 185 7 - 10 

T7 495 - 505 7 - 10 20 - 80 225 - 235 7 - 10 




MPa MPa % 



Al Si12CuNiMg F 200 200 160 100 190 170 100 70 ≤ 1 1.5 2.5 3 90 85 60 35 

Al Si18CuNiMg F 180 180 160 120 170 150 100 80 ≤ 1 1 2 3 90 90 70 50 


Al Si17Cu4Mg 2) F 180 180 160 120 170 150 100 80 ≤ 1 1 2 3 100 90 70 50 









°C °C °C % % % 


Al Cu4Ti 690 - 750 690 - 750 1.1 - 1.5 0.8 - 1.2 

Al Cu4MgTi 690 - 750 690 - 750 1.1 - 1.5 0.8 - 1.2 

Al Cu4TiMgAg 690 - 750 690 - 750 1.1 - 1.5 0.8 - 1.2 

Al Cu5NiCoSbZr 


690 - 750 690 - 750 1.1 - 1.5 

Al Si12CuNiMg 670 - 740 670 - 740 620 - 660 1.0 - 1.2 0.5 - 1.0 0.4 - 0.6 

Al Si18CuNiMg 730 - 760 730 - 760 730 - 760 0.6 - 1.0 0.4 - 0.8 0.3 - 0.6 


Al Si17Cu4Mg 1) 720 - 760 720 - 760 720 - 760 0.6 - 1.0 0.4 - 0.8 0.3 - 0.6 


Autodur 740 - 690 740 - 690 1.0 - 1.2 0.8 - 1.0 

Autodur(Fe) 700 - 650 0.5 - 0.8 


Al 99.7E 700 - 730 700 - 730 690 - 730 1.5 - 1.9 1.2 - 1.6 1.0 - 1.4 

Al 99.6E 


700 - 730 700 - 730 690 - 730 1.5 - 1.9 1.2 - 1.6 1.0 - 1.4 

94 


High-strength casting alloy 


These casting alloys are used for parts 

which – compared to all other aluminium 

casting alloys – require maximum strength. 

Where their reduced corrosion resistance 

represents no obstacles, these casting 

alloys can be used to manufacture high- 

strength components, for example, for 

the defence industry, aerospace, automotive, 

rail vehicles, mechanical engineering 

and the textile industry. 


The use of these relatively demanding 

casting alloys only makes sense if the 

component undergoes heat treatment. 

Only then, can the potential of these 

casting alloys be fully utilised. Following 

heat treatment, the castings still have excellent 

elongation as well as displaying 

the highest possible strength and hardness. 

This combination of high strength 

and good elongation values gives these 

casting alloys the highest possible Quality 

Index “Q”. 

By means of special heat treatment, 

hardness and elongation values can be 

adjusted within determined limits. There 

are other variants of these aluminium 

casting alloys, e.g. with nickel and cobalt 

being added to optimise their strength. 

Furthermore, there are also casting alloy 

types which contain silver so as to 

meet the maximum strength requirements. 

The corrosion resistance of cast 

pieces is reduced, however, due to the 

high copper content. 

The casting technique for these alloys is 

demanding. Most defects in the castings 

stem from “contamination” with silicon. 

The silicon content should be kept as 

low as possible and always lower than 

the iron content. An excess of silicon 

produces a low melting phase and increases 

the susceptibility to hot tearing 

during solidifi cation. Even slight impedi- 

ments to solidifi cation shrinkage can 

lead to structural separation. The most 

important requirement in the foundry is 

therefore cleanliness to prevent the takeup 

of silicon. Here are some recommendations: 

The melting crucible must not 

contain any remainder of silicon alloys. 

It also makes good sense to melt several 

batches of an alloy which is low in silicon 

in a new crucible to free the crucible 

material of silicon. There are users who, 

for this reason, use melting crucibles 

made of graphite or cast iron for these 

casting alloys. Return material should 

also be checked very strictly and stored 

separately; residual sand and other return 

material must be painstakingly removed 

from all sprues. From practical experience, 

some users recommend having a 

separate foundry department for these 

casting alloys. Melt cleaning and degassing 

can be carried out without any trouble 

using normal means. Melt treatment 

is restricted to grain refi nement which, 

among other things, slightly counteracts 

the susceptibility to hot cracking. Inten- 

sive grain refi nement is already performed 

by us so it does not usually need to be 

repeated in the foundry. The fl uidity of 

these casting alloys is comparable with 

other hypoeutectic AlSi casting alloys. 

The solidifi cation characteristics are best 

described as being globular-mushy. At 

approx. 90 K, the solidifi cation range is 

relatively high. Using a good fi lling system 

in conjunction with steered or controlled 

solidifi cation and suitable feeding, opti- 

mum structural qualities can be achieved 

with the sand and gravity die casting 

processes. Thanks to their good struc- 

tural quality and optimum heat treatment, 

these high-strength casting alloys are 

suitable for the manufacture of castings 

whose unmatched mechanical properties 

comply with maximum demands. 


High-strength casting alloy 


The heat treatment of castings is another 

important step in the production of quality 

cast parts. Exact temperature regulation 

of the annealing furnace, good tempera- 

ture distribution by means of circulating 

air and the correct positioning of the 

casting in the baskets, holders or racks 

are essential prerequisites for success. 

In solution annealing, the temperature 

increase should be moderate in order 

to allow enough time for temperature 

equalisation to take place in the castings 

and to avoid incipient fusion. The relief 

of casting strain, the removal of microstructural 

inhomogeneity and the diffusion 

of hardening constituents require 

longer periods of time. In these casting 

alloys, especially in thick-walled, slowsolidifying 

castings, stepped annealing 

96 


is recommended. First of all, the cast 

pieces undergo preliminary annealing 

at 480 to 490 °C for between 4 and 8 

hours; they are then given a solution heat 

treatment at approx. 515 to 535 °C for a 

further 6 to 10 hours. To avoid distortion, 

quenching of the casting after annealing 

can be effected by means of a water 

shower followed by immersion in warm 

water at temperatures of up to 80 °C. 

Fully-annealed Al Cu4TiMg castings have 

a susceptibility to stress corrosion. This 

condition is therefore not standardised 

for this casting alloy. Such parts are only 

used in naturally-aged condition (T4).

Piston alloys 


These casting alloys are used for cast- 

ings with wear-resistant surfaces and for 

structures which have to possess good 

strength properties at high temperatures. 

The main applications comprise: pistons 

for combustion engines, crankcases 

without additional cylinder liners, pump 

casings, valve casings, valve slides, gear 

elements etc. 


The wear resistance of these casting al- 

loys is due to many hard, rectangular or 

polygonal primary silicon crystals which 

are embedded in the ductile base mate- 

rial and jut out of the surface of the track 

with an edge (while the neighbouring 

troughs act as reservoirs for lubricant). 

In addition, alloying elements such as 

Cu, Mg or Ni give these casting alloys 

remarkable high-temperature strength. 

In order to produce as many small and 

evenly-distributed silicon crystals as 

possible in the cast structure, phosphorous 

is added. This treatment is already 

carried out during production of the ingots 

in our secondary smelters and, as 

a rule, does not need to be repeated by 

the foundry. The fl uidity of these types 

of casting alloy is very good. In spite of 

this, silicon crystals forming in the melt 

at too low casting temperatures are to 

be avoided because of their abrasive effect. 

Additional information is provided 

in the section on “Selecting aluminium 

casting alloys”. 


Self-hardening aluminium-silicon-zinc 



These casting alloys are used in the 

manufacture of models, foamed shapes, 

wearing parts or the bases of electric 

irons, for example. The use of these 

casting alloys is not recommended for 

machine parts which are subject to alternating 

or impact stress, are obliged 

to absorb bending and shearing stress 

or requiring a specifi c ductility. 

98 



The fl uidity of Autodur in particular is very 

good. Solidifi cation behaviour is similar 

to that of other casting alloys containing 

approx. 9 % silicon. Alloys of this type 

are self-hardening, i.e. after casting, the 

castings are stored at room tempera- 

ture and within approx. 10 days reach 

their service properties. This hardening 

takes place as a result of precipitation 

of the complex Al ZnMg. The advantage 

of these casting alloys lies exclusively 

in their saving of heat treatment costs. 

There are, however, disadvantages in 

using these casting alloys. The following 

information should serve as a warning: 

Under unfavourable conditions whilst 

molten, the zinc content is reduced due 

to its high vapour pressure. The resistance 

of Autodur to corrosion is sharply 

reduced as a result of its high zinc content 

of around 10 %. 

In cases where the exposure to corrosion 

is great or where parts made from Autodur 

are assembled with other castings or 

parts made from other aluminium alloys, 

or indeed fi tted to steel parts, there is a 

strong tendency to contact corrosion. 

Compared with all other aluminium cast- 

ing alloys, castings made from these al- 

loys display the lowest high-temperature 

strength. (Precipitation treatment carried 

out at room temperature to increase hard- 

ness has no clearly defi nable effect.) Ex- 

perience shows that castings, even after 

many years, can fracture spontaneously 

under the slightest impact or shock load. 

Over time, the microstructure appears to 

be embrittled.

Rotor aluminium 


This pure aluminium is mostly used in 

pressure die casting and goes into the 

manufacture of rotors (short-circuit armatures) 

and stators for the electric motor 

sector. It can also be cast into other 

construction elements which require 

high electrical and thermal conductivity. 


There is a particular hurdle in the near 

net shape casting of pure aluminium, 

i.e. sensitivity to hot tearing. The most 

important prerequisite for keeping this 

problem within limits is to maintain the 

correct ratio between iron and silicon. The 

silicon content must be as low as possible 

and the iron content must always be at 

least double the silicon content. Molten 

pure aluminium readily absorbs silicon 

from any standing material it comes into 

contact with. This can easily lead to an 

“imbalanced ratio”. Cleanliness is therefore 

important during processing and it 

is also essential to check tools and the 

melting crucible. In extreme emergencies 

when silicon enrichment occurs, it 

helps to increase the iron content within 

the permitted tolerance range. 



We have taken the relevant specialist 

literature into consideration while 

drawing up this Aluminium Casting 

Alloy Catalogue. Please do not hesitate 

to contact us if you require more 

detailed literary explanations. 

If you require any additional data or 

support at short notice, please refer 

to our contact details on the back 

of this brochure or simply visit us 

online at www.aleris.com. 


www.aleris.com 

Aleris 

Head offi ce Recycling Europe 

Aleris Recycling 

(German Works) GmbH 

Aluminiumstraße 3 

41515 Grevenbroich · Germany 

T +49 (0) 2181 1645 0 

Care has been taken to ensure that this information is 

accurate, but Aleris, including its subsidiaries, does not 

accept responsibility or liability for errors or information 

which is found to be misleading. 

Download any QR reader and scan. 

Charges may apply. 

Contact: T +49 (0) 261 891 7545 · info.europe@aleris.com · www.aleris.com © 2011, Aleris Switzerland GmbH 

Protective charge: 18 Euro Issue 12/11 · 1st release

Aluminium Casting Alloys - Aleris

Create successful ePaper yourself

Delete template?

Save as template?