Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 17: Magnetic Shape Memory Alloys

MA 17.8: Vortrag

Mittwoch, 28. März 2007, 17:00–17:15, H10

Directional solidification of Ni₄₈Mn₃₀Ga₂₂ magnetic shape memory alloys — •Martin Pötschke, Uwe Gaitzsch, Stefan Roth, Bernd Rellinghaus, and Ludwig Schultz — IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany

NiMnGa ferromagnetic shape memory (FSM) alloys have gained large research interest because of their possible application as actuator materials. The FSM effect is caused by the movement of twin boundaries by virtue of an external magnetic field. So far, this effect has only been observed in single crystals. The preparation of single crystals, however, is a long time and cost intensive process and both compositional changes along the crystal and segregation may occur. This is why for technical applications, there is a great interest in polycrystalline FSM materials. In order to extend the FSM effect to polycrystals, directional solidification was applied to prepare coarse grained, textured samples. Stationary casting in a pre-heated ceramic mold mounted on a copper plate was employed to generate a heat flow from the top of the cylindrical samples to the bottom and thereby a directional solidification in the opposite direction. The martensite start temperatures were checked by DSC, and the preferred growth direction and resulting textures were determined by EBSD. Further annealing, which is necessary for chemical homogeneity, results in grain coarsening and stress relaxation and affects the texture. The results of the investigation of the texture development during annealing will be presented.