Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 13: Computational Materials Modelling III - Alloys
MM 13.5: Vortrag
Montag, 26. März 2012, 16:45–17:00, TC 006
Ground-state structures and elastic properties of Ni-Ti-Hf shape memory alloys: An ab-initio study — •Jürgen Spitaler1,2, Daniel Lüftner1,2, Rostam Golesorkhtabar1,2, Peter Puschnig2, and Claudia Ambrosch-Draxl2 — 1Materials Center Leoben Forschung GmbH, Rosegger-Strasse 12, 8700 Leoben — 2Chair of Atomistic Modelling and Design of Materials, Montanuniversität Leoben, Franz-Josef-Strasse 18, 8700 Leoben
Ni-Ti-Hf is a promising shape-memory alloy due to its higher Martensitic transformation temperature as compared to pure NiTi. In this transformation, the energetics and elastic behavior of different crystallographic phases play a crucial role. We have determined the stable phases of NiTi1−xHfx in the monoclinic structure (B19’) as a function of the Hf concentration using the recently developed ATAT@WIEN2k interface. In order to improve the description of the disordered state, which is crucial for the quality of the expansion, special quasirandom structures were taken into account. We have determined the effective cluster interactions, based on the total energies of the fully-relaxed monoclinic supercells, which yields ordered groundstates for several Hf concentrations. The cluster expansion involves a rather high number of structures with positive formation energies, and it shows that Ti and Hf tend to form layers inside the unit cell. For the obtained groundstates we have determined the full elastic tensors and averaged macroscopic elastic properties structures applying ElaStic, a tool developed in our group.