Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 8: Magnetic Shape Memory Alloys

MA 8.11: Vortrag

Montag, 22. März 2010, 18:00–18:15, H22

Preparation and characterization of textured Ni-Mn-Ga to show MFIS — •Martin Pötschke, Claudia Hürrich, Stefan Roth, Bernd Rellinghaus, and Ludwig Schultz — IFW Dresden

Ni-Mn-Ga alloys are interesting because of their possible application as magnetic shape memory materials. This effect is caused by the motion of twin boundaries in a magnetic field. Up to now most of the research was concentrated on single crystals. However, the preparation of single crystals is a time consuming and cost intensive process and compositional changes along the growth axis as well as segregations may occur. This is why for technical applications there is a great interest in polycrystals, which are easier to produce. To achieve magnetic field induced twin boundary motion in polycrystals, directional solidification was applied to a 5M Ni-Mn-Ga alloy in order 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 towards the bottom of the sample and thereby a directional solidification in the opposite direction. The preferred solidification-induced growth direction was determined by EBSD. Annealing is necessary for homogenization and stress relaxation. The martensitic transformation temperature which strongly depends on the composition was monitored by DSC, and it is shown that the chemical homogeneity along the sample axis is improved in likewise treated samples. After a mechanical training process MFIS was observed.

Financial support by the DFG within SPP 1239.