Dresden 2017 – wissenschaftliches Programm
MM 47.4: Vortrag
Mittwoch, 22. März 2017, 16:45–17:00, BAR 205
First-principles insight into the martensitic transformation and diffusion properties in Ti-Ta alloys — •Tanmoy Chakraborty, Jutta Rogal, and Ralf Drautz — Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universität Bochum, 44780 Bochum, Germany
In Ti-Ta-based high-temperature shape memory alloys (HTSMAs) the martensitic transformation temperature (Ms) exhibits a strong dependence on the chemical composition. A detailed knowledge of the underlying mechanisms and phase stability of the competing austenite and martensite phases in these alloys can aid the design of new HTSMAs with the desired functional properties at elevated temperatures. Using density functional theory in combination with the quasi-harmonic Debye model we approximate the different contributions to the free energy as a function of composition and compare the stability of competing phases at finite temperature. We identify the physical key parameters governing the experimentally observed composition dependence: the 0K energy difference and the difference in the Debye temperature between the involved phases. From our calculations we propose a one dimensional descriptor for high-throughput screening of Ms for the design of new HTSMAs. In addition to the thermodynamic phase stability we investigate the mobility of the different elements within the alloy as a function of composition and local environments which is key to analyze segregation and redistribution at elevated temperatures.