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MA: Magnetismus

MA 4: Magnetic Materials I

MA 4.6: Vortrag

Montag, 27. März 2006, 11:30–11:45, HSZ 401

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

NiMnGa alloys are among the most intensively studied magnetic shape memory (MSM) materials. The MSM effect is caused by the movement of twin boundaries in a magnetic field. So far, this effect has only been observed in single crystals. The preparation of single crystals, however, is a long time process and thus expensive, and compositional changes along the crystal axis may arise.To expand the MSM effect to polycrystals, directional solidification was applied in order to prepare coarse grained, textured samples. The technique of stationary casting in a preheated ceramic mold mounted on a copper plate was chosen to provide a heat flow towards the bottom of the mold and therefore a directional solidification in the opposite direction. In order to allow for a direct investigation of the resulting microstructure by EBSD measurements, an alloy composition with a martensitic transformation temperature below room temperature was chosen. The transformation temperature was checked by DSC. The preferred growth direction was determined by EBSD.