Phases in Ni based ternary alloys - Science Initiative Group

Materials research at the University of
Botswana: Phases in Ni based ternary alloys # .
Pushpendra K Jain†
Professor of Physics, and
Coordinator: AMSEN* - UB Node
University of Botswana
Gaborone, Botswana
Ph: +267 7151 9489
email: jainpk@mopipi.ub.bw
(#) Seminar @ UCONN, Physics, Storrs, CT, USA, 29 May 2012.
(*) African Materials Science and Engineering Network,
A Carnegie – IAS RISE Network.

(†) UCONN Alumni
Class of 1975: PhD Physics
1. Introduction: Botswana
2. University of Botswana
3. FoS Shared Research
Facilities
4. Materials Research
Funding: AMSEN
5. Phases in Ni - super alloys.
6. The Ni – Ru – Zr system
7. Sample preparation
8. SEM, EDX and XRD analysis
9. Solidus & Liquidus
projections.

Republic of Botswana
Location: 17 o – 27 o S
20 o – 30 o E
Area: 224 607 Sq mi
(581 730 Sq km)
(~ Size of France)
Population: 2 Million
GNP: ~ 8 Billion US$
(Upper Middle Income)
Economy: Diamonds
Beef products
Cattle: 3-4 Million

Capital city: Gaborone

University of Botswana (UB)

1964: UBBS
1966: UBLS
1975: UBS
1982: UB Established.
•2 Schools + 7 Faculties
Faculty of Science:
7 Departments
1. Biology 2. Chemistry
2011-2012: Present status 3. Computer Science
•Staff: 2,679
4. Environmental Science
Academic: 823
•Students: 15,731
Full time: 12,626
Graduate: 1,391
(PGDiploma, MA, MPhil, PhD)
5. Geology 6. Mathematics
7. PHYSICS
Research Facilities:
Faculty Shared
Department based.

Faculty of Science Shared Facilities
7 Research and support Units: Each unit
Managed by a Department.
Headed by a Research Scientist
Assisted by Technical staff.
Electron Microscope Unit
X-ray Diffraction Unit
(Geology)
Inductively Coupled MSU
(Geology)
Mass Spectroscopic Unit
(Chemistry)
NMR Unit
(Chemistry)
Glass blowing (support) unit (Chemistry)
Liquid nitrogen plant (support) (Physics)
(Physics)

Electron Microscope Unit (EMU)
•XL 30 ESEM with EDX
•Technai 12 TEM
•Accessories and Ancillaries for
SEM and TEM.
•Light Microscopes (LM):
•Zeiss Axioskp Transmitted LM
•Nikon SMZ 100 Stereo LM
•Axiovert 200 Mat Inverted LM

X-ray Diffraction Unit (XRDU)
•Philips PW 3710 mpd
controlled XRD with PW 1752
graphite monochromator.
o PW 1830 Generator
o PW 3020 vertical goniometer
o PW 3011 Xe detector
o PW 1386/55 auto divergence slit
o X’PERT 2000 data collection and
analysis software
o V30 water chiller, and
o V40 compressor

Inductively Coupled Mass Spectrometer Unit
(ICPMSU)
•Finnigan MAT Element 2
High Resolution ICPMS
o
o
CETAC LSX-200 Plus
Laser Ablation (LA)
Varian Pro-Star High
Performance Liquid
Chromatograph (HPCL)

Mass Spectroscopy Unit (MSU)
•Finnigan Mat SSQ 7000 MS
single quadrupole with GC-MS,
EI, CI, APCI, and ESI facilities.
•LCQ DECA Ion Trap MS
(with a dedicated
chromatographic system, an auto
sampler, and a diode array
detector.)
Can be coupled to a micro-high
performance anion exchange
chromatographic (HPAEC)
system or a Capillary
electrophoresis (CE) system.
•Over 240 000 Spectra library.

Nuclear Magnetic Resonance Unit (NMRU)
•Bruker DMX Avance 300
NMR Unit with QNP and BBI
probes (2) and a 60 sample
changer carousel.
•Bruker DRX Avance 600
NMR Unit with Selective
Inverse, Dual and Broad
Band probes (3)

Departmental Research Labs.
PHYSICS:
•Thin films deposition
and characterization lab.
o Edwards Auto 500 RF
Magnetron sputtering unit.
o KLA-Tencor P15 Surface
Profiler (Accuracy: ±15 Å).
o Varian CAREY 500 UV -
Visible – NIR Spectrometer
for solid and thin film
samples.
MECHANICAL ENGG:
•Materials testing Lab.
PHYSICS - Other Research:
•Geophysics Research Lab.
•Atmospheric Pollution
Studies Lab.
•Radiation Physics Lab.
•Solar Radiation
Measurement Lab.

Materials Research Funding:
The AMSEN Project
AMSEN: The African Materials Science and
Engineering Network:
A Carnegie – IAS – RISE Network of 5 African Universities:
•University of Botswana
• U. Namibia
•Wits University, South Africa
• U. Nairobi (Kenya)
•Federal University of Technology, Akure, Nigeria
•Funded by Carnegie Corporation through the
Regional Initiative in Science and Education (RISE) at the
Institute of Advanced Study (IAS) Princeton, USA.
Phase1: 2008 – 2011 (Completed)
Phase 2: 2011 – 2013 – On going.
Beyond 2013: Negotiations with World Bank: (To scale up x4).

Objectives of AMSEN
• Capacity building in Materials Research through
Manpower Training.
Training of new staff at MPhil/ PhD level.
Building supervisory capacity thru co-supervision.
Creation of research facilities and infrastructure.
New equipment/ repair/ maintenance/ sharing.
•AMSEN funding used for:
Full students’ bursaries – Tuition/ Medical/ Personal.
Research cost – materials and publications cost.
Equipment – repair, maintenance, new equipment.
Training - workshops and short courses.
Travel - conferences, workshops and research visits.

AMSEN at UB:
UB Node of AMSEN Coordinated by Pushpendra Jain
• 2 PhD + 2 MPhil students at UB working on:
Composite systems using organic fibers.
Si – In – Bi Thin films: Phase change materials for
data storage.
Ni based ternary alloys – Supervised by myself (PKJ):
Ni – Ru – V system (Part-time PhD student I Physics)
Ni – Ru – Zr system (MPhil student in Mech Engg.)
•Co-supervision (PKJ) of a PhD student at Wits and a
MSc student at Nairobi (Completed – December 2011).
•Have organized 5 short training courses/ workshops to date for
staff and students from all AMSEN nodes.
•Staff and students have attended Conferences/ workshop.

UB – AMSEN Family: An Introduction
Batane, Chipise, Rabalone, Jain, Coetzee, Sathiaraj, Muiva
CORNISH MODISI MOKALOBA FLORANCE
March 2012
17

Phases in Ternary Alloys: Work at UB
• Ni based Ternary alloys (Super alloys):
Ni-Ru-Y system: MPhil – Stephen (Completed)
Ni-Ru-Zr system: MPhil – Liberty (Ongoing)
Ni-Ru-V system: PhD – Stephan (Ongoing)
(Potential application: Jet engine and Power turbines).
• Ni-V-C being investigated by Apata (PhD) at Wits
University (Co-supervised by PKJ):
(Potential application in high corrosion petrochemical and
related industries.)
•Our focus today is on Ni-based super alloys.

Ni based supper alloys
Super alloys:
oHigh Temperature application: ~0.8 x melting temp.
oHigh creep and oxidation resistance at high temp.
oHigh corrosion resistance at high temp.
oCommon super alloys: Iron, Cobalt, Nickel based.
•Ni (melting temp: 1455 o C) super alloys suited for
jet engines and turbines applications.
oTo increase their temperature of operation (say
~1300 o C) to achieve:
Improved efficiency,
Reduced fuel consumption,
Reduced environmental pollution.

Alloying Additives: Why and Which?
•Alloying additives in steels are used to:
Solid solution strengthening.
Improve corrosion resistance.
Improve hardenability.
Phase stability.
Reduce rate of tempering…..
•Physical Parameters to Consider:
•Atomic size factor: For Ni alloys: V, Cr, Fe. Mn. etc.
•Solubility factor: For Ni alloys: Ru, V, Cr, Ti, Al, Au, Cu, W.
•Diffusivity: W, Mo, Cr, V, Fe, Co, Au, Cu.
•Crystal structure: Ni 3 X compounds with FCC structure
where X → Al, Ti, V, Mn, Fe, Mo, Co etc.

Ru:
Choice of Ni based Ternaries!
• Increases corrosion resistance of stainless
steels and Ti alloys.
• Extensive solubility of Ni and Ru
→ Our focus is on Ni-Ru binary for Ni super alloys.
Y: Surface stabilizer by forming oxides.
V: Atomic size factor and diffusivity.
Zr: Alleviates embrittlement of internal surfaces like
grain boundaries.
→ We Considered 3 Ni based ternaries not
found in literature:
Ni-Ru-Y; Ni-Ru-V; and Ni-Ru-Zr

Binary systems
• Are essential to interpret
the analysis of ternaries.
•A binary phase diagram
(@ constant pressure) has
at% (wt%) composition
along the horizontal and
temperature along the
vertical.
•Liqidus and solidus
curves separate all liquid
and all solid phases from
the mixed phase regions,
for example: →
Binary PD of completely
miscible liquids and
completely immiscible solids
(with eutectic reaction):

Binaries associated with a ternary
•3 Binaries are associated with a ternary system.
•From the binary PDs solidification reaction and
the binary phases at different compositions are
deduced as a function of temperature.
•All known binary systems are all well
understood and extensively studied.
•These PDs could be quite complex .
•For example, binaries associated with the
Ni – Ru - Zr ternary are Ni - Ru, Ni - Zr, Ru - Zr as
shown in the following slides:

Ni – Ru binary (Massalki 2007)
(Simple peritectic system)

Ni – Zr binary (Okamoto 1993)
(Complex system with Eight intermetallic phases)

Ru – Zr binary (Okamoto 2007)
(Two intermetallic phases)

Ternary Phase Diagram
•Are plotted in 3D.
•3 axis along an equilateral
∆ in the horizontal plane
give ternary composition.
•Temperature is along the
vertical axis.
•Vertical planes through
the sides of the ∆
correspond to the binary
PDs.
•Liquidus and solidus
curves in binary PDs
become the surfaces.

Isothermal section of the ternary PD
•An isothermal section of a
ternary PD is an equilateral
triangular composition grid.
•(X-) along the three axis gives
the at% (wt%) composition of
each constituent A, B and C of
the ternary.
•We use such composition grids
to analyze phase composition
data, to display the phases and
extent of phases, and liquidus
and solidus projection of our
ternary systems.

Materials and sample preparation
•99.9% pure elements are used for the alloy samples.
(Adds to the high cost of consumables).
•Large % of Impurities if present results in an alloy of
higher order than ternary.
•Samples are made in batches of 6, limited by the furnace
design.
•First batch of samples is chosen to be equally spaced on
the ternary composition grid.
•Constituent elements for a 2g sample are weighed,
mixed thoroughly, and compacted in to a pallet.
•Compacted pallets are melted in an arc furnace with
water cooled copper hearth in an argon atmosphere to
prepare “2 g alloy buttons”.

First
batch of
six alloy
samples

At% composition of the first batch of
six samples of Ni-Ru-Zr alloy.
Sample Ni at% Ru at% Zr at%
1 20 40 40
2 20 60 20
3 20 20 60
4 40 20 40
5 60 20 20
6 40 40 20

Representative mass calculation for a 2g
Ni 20 : Ru 40 :Zr 40 alloy sample..
Sample Element
Atomic
Mass At %
Mass (g)
in
sample
Mass (g)
in 2g
sample
Ni 58.6934 20.00% 11.73868 0.2648
Ru 101.0700 40.00% 40.42800 0.9120
1
Zr 91.2240 40.00% 36.48960 0.8231
SUM 250.9874 100.00% 88.65628 2

Arc melting of alloy samples
•6 compacted pallets and a “Tioxygen
getter “are placed inside
the furnace with a dome and a
viewing window.
• Dome is evacuated, flushed with
“Pure argon”; process repeated 3
times, and then filled with argon.
•Ti is melted first to absorb traces
of O 2 by oxidation of Ti.
•Next the pallets are melted to cast
the alloy buttons.
•Each button is turned and melted
again; process repeated 3 times for
thorough mixing.

Metallographic preparation of as cast samples
•Alloy buttons are sectioned in two halves;
one half preserved for heat treatment studies later;
and
Second half is prepared for as-cast sample analysis.
•The second half is mounted in cold epoxy resin; ground
on successive grade (#25 0→ #2400) emery papers to
remove cutting-scratches; polished to 1µm finish with
diamond paste.
•Polished samples given a thin carbon coating to prepare
them for SEM analysis.
•BSE imaging and EDX analysis are used as the SEM
analytical tools to deduce solidification reactions and
determine phases compositions.

Samples analysis: Solidification reactions
•Phases distinguished from contrast in Back scatter electron
(BSE)-SEM image, (larger atomic number → brighter image).
•Orientation, and coring also effects contrast.
•Solidification reactions are inferred from shapes of the
phases, e.g..
Oxides, if any, are the first to form and do not participate
solidification reactions, may act as nucleation sites.
Dendrites/ needles are the first to solidify.
Liquid then solidifies outwards from the dendrites.
Irregular (chewed-up) edges of the solid phase point to
peritectic reaction .
Eutectic is the last to solidify as a mix of dark and light regions
from simultaneous growth of two or more phases. (zebra like
appearance).

BSE – SEM images of some
solidification processes

BSE Image of and Phases in as cast
Ni 19 :Ru 20 :Zr 61

Solidification reactions in as cast
Ni 19 :Ru 20 :Zr 61
L → Light
L + Light → Medium dark,
locally.
L + Medium dark →
Medium, locally
L + Light → Medium
L → ~ZrRu
(L + ~ZrRu → τ 2 locally)
L + τ 2 → ~Zr 2 Ni, locally)
L + ~ZrRu → ~Zr 2 Ni.

Sample analysis: Phase compositions
•Composition of different contrast regions (phases) is
determined from EDX analysis.
•Final composition is the mean of at least five analyses of the
same contrast region.
•A region must be at least 3µm across for accurate analysis.
•Smaller regions are effected by the neighboring regions
resulting in large uncertainty.
•Composition of all the phases are plotted on the ternary
composition grid.
•The overall composition must fall within the area enclosed
by the tie lines of the identified phases.
•Phases are tentative identified by comparing the points on
the plot to the nearest binary phases.

EDX analysis of as cast
Ni 19 :Ru 20 :Zr 61
Phase Description
Composition at.%
Ni Ru Zr
Overall 18.8±0.2 19.9 ±0.3 61.3± 0.1
Light (dendrites) 12.9±0.4 38.8±0.7 48.3±0.3
Inner-dendritic (ID) 13.6±1.0 38.1±0.9 48.4±0.2
Medium 24.6±0.5 10.0±0.5 65.4±0.6
Medium dark 20.7±0.5 6.1±0.4 73.2±0.2
Dark 13.3±0.1 4.0±0.4 83.0±0.2

EDX plot of as cast Ni 19 :Ru 20 :Zr 61
on Ternary Composition Grid

Sample analysis: Phase identification
•Phases are confirmed and identified from the XRD
analysis of the samples and by matching peaks from the
data base.
•As known binary phases of our ternary system are all
known, the unidentified peaks in the XRD spectra point to
new ternary phases. In the system.
•Position of the unidentified phases on the ternary plot
support the presence of ternary phases in the system as
such points are far from the known binary phases.
•Next we go back to solidification reaction, and express
them in terms of the phases identified.

XRD spectra of as cast
Ni 19 :Ru 20 :Zr 61
Counts
NiRuZr4
1000
Ru Zr; Zr2 Ni
500
Zr2 Ni
Ru Zr
Zr2 Ni
0
30 40 50 60 70 80
Position [°2Theta] (Copper (Cu))

More samples analysis
•This is the complete storey of analysis of one sample.
•Likewise all the six samples in the batch are analyzed, and
plotted together on the ternary composition grid.
•Next a second batch of six samples is cast with
compositions selected to fill the gaps on the composition
grid; samples analyzed, and plotted on the same grid with
the first batch.
•Finally third batch of six samples is cast to fill the
remaining gaps or to investigate certain region of the grid in
details; samples analyzed.
•In the end we have 18 samples plotted on the grid.
•This is generally sufficient data to be able plot solidus
surface and liquidus projection of the ternary system.

18 samples plot of the Ni-Ru-Zr
ternary alloy

Solidus projection surface of the Ni-Ru-Zr
ternary alloy

Liquidus projection surface of the
Ni-Ru-Zr ternary alloy

Conclusion and further work
•Phases in as cast Ni-Ru-Zr alloy are identified,
•Four new ternary phases were found.
τ 1 with composition ~Zr 24 Ru 31 Ni 45
τ 2 with composition ~Zr 79 Ru 3 Ni 18
τ 3 with composition ~Zr 34 Ru 4 Ni 62 , and
τ 4 with composition ~Zr 47 Ru 22 Ni 31
To study at least one sample of composition Ni 27 :Ru 63 :Zr 10
at.%, to verify the direction of the liquidus surface
To anneal as-cast samples for isothermal section.
To determine the crystal structures of the ternary phases.

“Millennium Etched in a Rock: A Geological Calendar”
First Prize: Micrograph Competition – MSSA2005,
44th Annual Conference of the MSSA, December 2005,
and
Image of Distinction Award: Nikon’s Small World 2009

Jain family: December 2011