Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
MM: Fachverband Metall- und Materialphysik
MM 72: Magnetic Shape Memory Alloys (joint with MA)
MM 72.3: Vortrag
Freitag, 16. März 2018, 10:00–10:15, TC 010
Martensitic transformations in Ni2MnGa alloy: a first-principles study — •Martin Zelený1,2, Ladislav Straka2,3, Alexei Sozinov4, and Oleg Heczko2,3 — 1NETME Centre, Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic — 2Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic — 3Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic — 4Material Physics Laboratory, Lappeenranta University of Technology, Savonlinna, Finland
The martensitic transformation paths in Ni2MnGa alloy from cubic austenite to several low-symmetry martensitic structures have been studied by first-principles calculations combined with the generalized solid state nudged elastic band method. We determined the minimum energy path and corresponding changes in crystal lattice leading to the four-, five-, and seven-layered modulated phases of martensite (4O, 10M, and 14M) described as the relaxed nanotwinned non-modulated (NM) phase. In the transformation to the 10M phase there is no energy barrier on the path and energy decreases with a large negative slope. Initially, these transformations are driven by a softening of the TA2 [ξξ0] phonon branch corresponding to the shift of (110) planes. Transformation paths to other structures exhibit more or less significant barriers in the beginning of the path, hindering such a transformation from austenite. This finding corresponds to experiment and demonstrates that the kinetics of the transformation is decisive for the selection of the particular low-symmetry structure of martensite.