Regensburg 2019 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 27: Methods in Computational Materials Modelling (methodological aspects, numerics)
MM 27.12: Talk
Wednesday, April 3, 2019, 18:00–18:15, H44
An ab initio perspective on reversible martensitic transformations in Ti-Ta shape memory alloys — •Alberto Ferrari1, Davide G. Sangiovanni1,2, Jutta Rogal1, and Ralf Drautz1 — 1Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universität Bochum, 44801 Bochum, Germany — 2Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden
Shape memory alloys exhibit reversible martensitic transformations (MTs) when temperature or stresses are applied. Modelling these transformations from first principles is not trivial, since static calculations are usually not sufficient to explore the most important aspects of the MTs, such as the Ehrenfest order of the phase transitions, the range of stability of the low- and high-temperature phases, and their free energy barrier. In this contribution, a fully ab initio strategy to characterize MTs in alloys is presented. The temperature dependent order parameters of a MT are calculated with ab initio molecular dynamics; then, the free energy of the MT, from which all the relevant thermodynamic properties of the MT can be derived, is modelled with a Landau polynomial expansion. The parameters of this expansion are completely extracted from first principles. This approach is applied to the high-temperature shape memory alloy Ti-Ta, for which very small values for the free energy barrier and the region of metastability are observed.