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Preparation of textured Ni48Mn30Ga22 |
Martin Pötschke , Uwe Gaitzsch , Stefan Roth , Bernd Rellinghaus , Ludwig Schultz |
Leibniz-Institute for Solid State and Materials Research, P.O.Box 270116, Dresden D-01171, Germany |
Abstract |
NiMnGa alloys have gained large research interest because of their possible application as magnetic shape memory materials. This effect is caused by the movement of twin boundaries in a magnetic field. So far this effect has only been shown in single crystals. The preparation of single crystals is a long time and cost intensive process and there can be compositional changes along the crystal and segregations. That is why for technical applications there is a great interest in polycrystals. To expand this effect to polycrystals, directional solidification was applied in order to get a coarse grained, textured sample. The technique of stationary casting in a preheated ceramic mold mounted on a copper plate was chosen in order to have a heat flow from the sample to the bottom and therefore a directional solidification in the opposite direction. To achieve a higher mold temperature at cast an additional heater was built and used for the casting process. The transformation temperature was checked by DSC. Since the transformation temperature strongly depends on composition, chemical homogieniety along the sample axis was approved by using this method. The preferred growth direction was determined by EBSD. Further annealing, which is necessary for chemical homogeneity, coarsening of grains and stress relaxation, influences the texture. Investigations on the texture development during annealing were done. |
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Presentation: Oral at E-MRS Fall Meeting 2007, Symposium E, by Martin PötschkeSee On-line Journal of E-MRS Fall Meeting 2007 Submitted: 2007-05-11 13:30 Revised: 2009-06-07 00:44 |