Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 8: Magnetic Shape Memory Alloys

MA 8.5: Talk

Monday, March 22, 2010, 16:15–16:30, H22

A phase-field model for twin boundary motion in martensitic microstructures — •Christian Mennerich, Marcus Jainta, Frank Wendler, and Britta Nestler — Karlsruhe University of Applied Sciences, Karlsruhe, Germany

Magnetic shape memory (MSM) alloys are of great interest, e.g. for building actuators providing large deformations and rapid responses. Fundamental for the magnetic shape memory effect is the microstructure evolution in the twinned martensitic state of MSM materials under applied external magnetic fields. An existing phase-field model, basing on a free energy functional of the Ginzburg-Landau type, is extended by micromagnetic and elastic energy contributions, with the aim to model and predict the magnetically induced twin boundary evolution in martensitic microstructures. Assuming an isothermal setting below the Curie temperature and the martensitic start temperature, this model is appropriate to describe the diffusionless phase transition responsible for twin boundary motions. We give the derivation of the model extensions, resulting in a system of coupled partial differential equations, and solution strategies for a scheme using finite differences. With this model, the time-spatial evolution of the volume fractions of martensitic variants, of the displacement field for elasticity and of the micromagnetic domain wall structure can be described. Finally, we present simulation results demonstrating magnetically induced twin boundary motions.