Dresden 2011 – scientific programme

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MA: Fachverband Magnetismus

MA 25: Magnetic Shape Memory Alloys II (jointly with MM)

MA 25.3: Talk

Tuesday, March 15, 2011, 14:00–14:15, HSZ 103

Textured Ni-Mn-Ga as a material for magnetically driven actuators — •Martin Pötschke, Jan Romberg, Claudia Hürrich, Stefan Roth, and Ludwig Schultz — IFW Dresden, Institute for Metallic Materials, P. O. Box 270116, 01069 Dresden, Germany

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. The samples show a <100> fibre-texture. Annealing is necessary for homogenization and stress relaxation. After the annealing the samples showed chemical homogeneity along the sample axis. A two-side mechanical training was applied to decrease the stress, which is necessary to move the twinboundaries. The stress-strain curves for the two training directions show a different behaviour. Also the magnetically inducable stress is different for the two directions. This influences the magnetic-field-induced strain (MFIS). A resettable MFIS was measured in samples with a plate-like geometry.

Financial support was provided by the DFG within SPP 1239.