Ab initio plane wave based density functional calculations within the generalised gradient
approximation (GGA) have been carried out on a wide range of phases and stoichiometries
for the platinum-titanium (Pt-Ti) and iridium-titanium (Ir-Ti) alloy systems, using
the Vienna Ab Initio Simulation Package (VASP) with projector augmented wave (PAW)
potentials.
For all of the phases in this work, the equilibrium structures were found by performing
a full relaxation of the atoms. There were 20 di erent phases considered for varying
atomic percentage compositions for each alloy system. Energy-volume calculations and
heats of formations were used to determined the equilibrium structures at each atomice
percentage composition and to determine if there were high temperature phases at that
composition. The elastic constants and elastic moduli are calculated and the electronic
structure and density of states (DOS) were considered to understand the hardness and
stability properties of the alloys.
For the Pt-Ti system, the low and high temperature phases at di erent compositions
agreed with previously published results in the literature. Intermediate phases at 50%
were also determined, in agreement with previous results. Alloying Pt with Ti resulted in
a decrease in the bulk modulus, i.e. not adding strength to the metal. However, the shear
modulus increased for most of the alloys compared to bulk Pt and it was found that in
general, alloying may increase the resistance to shear. PtTi alloys were found to be ductile
in nature, as with both constituent metals in their bulk form.
In the Ir-Ti system, bulk Ir was found to have the highest bulk, shear and Young's modulus
with each of these values decreasing with increasing percentage Ti in the alloy. IrTi
alloys with 66.7% Ir composition or higher were found to be brittle in nature, similar in
behaviour to bulk Ir; alloys with a higher percentage concentration of Ti were found to be
ductile. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/7964 |
| Date | January 2011 |
| Creators | Cavero, Miguel. |
| Contributors | Pierrus, John. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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