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Abstract

Ti-Ta alloys are high temperature shape memory alloys, featuring a martensitic transformation between the β phase and the α'' phase. 0 K electronic structure calculations are not able to clarify two aspects of this phase transformation: firstly, they cannot characterize the mechanism according to which β, dynamically unstable at 0 K, becomes stable at higher temperatures; secondly, the minimum energy path for the phase transformation calculated at 0 K suggests a second order phase transition, in disagreement with experiments, which indicate a first-order process. This poster presents ab-initio molecular dynamics simulations on Ti-25Ta and Ti-31.25Ta. Using the temperature dependence of the structural parameters of the phases, we are able to detect the transition temperature for the phase transformation. Furthermore, we show how a discontinuity in the average atomic positions hints towards a first order transformation, solving the controversy with the experiments.