Regensburg 2004 – wissenschaftliches Programm
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MA: Magnetismus
MA 24: Symposium Magnetic Shape Memory Alloys (zusammen mit M)
MA 24.4: Vortrag
Donnerstag, 11. März 2004, 12:30–12:45, H23
MAGNETIC-FIELD-INDUCED STRAINS IN FERROMAGNETIC SHAPE-MEMORY ALLOYS — •U.K. Rößler1, A.N. Bogdanov1,2, A. DeSimone3, S. Müller2, and F. Otto4 — 1Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Postfach 270116, 01171 Dresden — 2Max-Planck-Institut für Mathematik in den Naturwissenschaften, Inselstr. 22 - 26, 04103 Leipzig — 3International School for Advanced Studies, via Beirut 2-4, 34014 Trieste — 4Institut für Angewandte Mathematik, Universität Bonn, Wegelerstr. 10, 53115 Bonn
Phenomenological equations for multivariant states in a ferromagnetic martensitic materials have been derived [1]. We apply the theory to describe the evolution of a tetragonal twinned martensitic microstructure consisting of two variants. Analytical solutions for the components of the strain tensor can be obtained as functions of external stresses and the volume fractions of the twin variants. Equilibrium magnetic parameters have been calculated within phase theory approximation and for a model of stripe domains. Critical lines between multivariant (twinned) states and the two types of homogeneous states and corresponding field-stress phase diagrams have been calculated. Sufficiently high stresses can block multivariant states. Then, the transition between the two homogeneous states occurs as a first-order process. Time-dependent processes can be simulated based on a kinetic equation within this phenomenological theory.
[1] A.N. Bogdanov, A. DeSimone, S. Müller, U.K. Rößler, J. Magn. Magn. Mater. 261, 204 (2003).