Dresden 2014 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 6: Microstructure and Phase Transformations I - Martensitic phase transformations
MM 6.1: Talk
Monday, March 31, 2014, 10:15–10:30, IFW B
Nucleation and growth of martensite in epitaxial magnetic shape memory films — •Robert Niemann1,2, Anja Backen1, Hanuš Seiner3, Sandra Kauffmann-Weiss1,4, Christian Behler1,2,4, Ulrich K. Rößler1, Ludwig Schultz1,2, and Sebastian Fähler1,2,4 — 1IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany — 2Technische Universität Dresden, Department of Physics, Institute for Solid State Physics, 01062 Dresden, Germany — 3Institute of Thermomechanics, ASCR, Dolejškova 1402/5, 182 00 Prague, Czech Republic — 4Technische Universität Chemnitz, Faculty of Natural Sciences, Institute of Physics, D-09107 Chemnitz, Germany
The complex martensitic microstructure of modulated magnetic shape memory alloys is beneficial for magnetic field induced reorientation or reversible field induced phase transition [1]. The big difference in mobility between type I and type II twin boundaries highlights the importance of a monoclinic description of the lattice. Hence it is important to understand the microstructure from the atomic up to the macroscale. As a model system we analyze the martensitic transformation in epitaxial Ni-Mn-Ga films. We perform temperature dependent SEM imaging during the phase transition and XRD as well as TEM in the martensitic state. We describe the observed stages of nucleation and growth using a crystallographic model based on the Wechsler-Lieberman-Read theory of martensites and finite element methods. [1] R. Niemann et al., Adv. Eng. Mat. 14, 562 (2012)
Supported by SPP1599 www.FerroicCooling.com