Thixoforming : Semi-solid Metal Processing

9.2 SSM Casting Processesj317
For these reasons, the same production rates as with conventional methods still
cannot be reached for the relatively young thixocasting process. Finally, the choice of
safety parts in the driving work area and other sensitive components is important.
The high mechanical requirements and the small fault sizes have led to high scrap
rates. The boundary conditions for use turned out to be increasingly difficult since
there were a growing number of methods with similar possible applications. The
Vacural pressure die-casting, the Poral method and the Cobapress method were
alternatives in the chassis suspension, and also the squeeze casting method and a
modern ingot casting [20]. Thixoforming has become the production alternative for
very qualitative aluminium components, [21] which deliver good quality [22] but is
more expensive than alternative methods. In this situation, these competing methods
have fully exploited their potential, and thixoforming has only seldom been
adopted. Thixalloy Components GmbH, as a motorcar sub-supplier of high-strength
castings, decoration parts, solderable parts and also structural parts, is currently a
successful company with annual sales of more than 4 million euros.
At that time, particle amplified and also over-eutectic alloys also offered further
material classes. It was known that an unwanted separation of particles and metal
melt could occur due to the density difference between the metal and particles during
processing in the normal die-casting process. Because of the high content of solid
phase in processing in the semi-solid area, this phenomenon is a considerably
restricted. First examinations were carried out on AlSi-based alloys with SiC or TiB 2
particle additions [1, 5]. The wear-resistant alloys AlSi17Cu4Mg and AlSi25CuMgNi
also could be processed by thixocasting [23, 24] and show comparably high wear
resistances with respect to a metal–matrix composites (MMCs).
Until now, the conventional die casting of high-melting point is practicable only for
some brass-based materials. The two standardized copper–zinc pressure die-cast
alloys CuZn37Pb and CuZn15Si4 show a liquid interval between 890 and 910 C and
830 and 900 C, respectively. The high pouring temperatures, however, generally do
not allow very long form stand times of approximately 10 000 parts.
In first examinations, it was reported that the mechanical qualities of thixocast
model components of the copper bronze CDA905 are similar to those of conventionally
cast parts [25, 26].
The development of copper pressure die-casting has attracted greater attention in
the newer literature for the electrical industry despite the load on the tools. To
improve the degree of effectiveness and the load alternation behaviour, aluminium
pressure die-casting rotors and cages could be replaced with copper pressure
die-casting of energy-saving three-phase motors [27]. Examinations have already
been carried out successfully of die-casting copper-based alloys in the semi-solid
state [28]. Different sample components were produced for the determination of
properties [29, 30].
The wide alloying range of modern steel materials makes possible broad variations
of the quality profile through which numerous industrial applications become
possible in combination with adapted heat treatment strategies. Steel is still therefore
one of the s most frequently used structural materials worldwide [31]. Steel materials
offer an often equal or sometimes even higher lightweight construction potential