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Martensitic transformation in melt-spun NiMnGa ribbons
|Jozef Lelatko 1, Tomasz Goryczka 1, Patrick Ochin 2, Henryk Morawiec 1|
1. University of Silesia, Institute of Materials Science, 12, Bankowa Str., Katowice 40-007, Poland
Ferromagnetic shape memory alloys have been extensively studied since they were first time reported by Webster. He found that in a ternary intermetalic Ni2MnGa alloy the parent phase, despite of the thermal and stress gradients, transforms to the martensite in a ferromagnetic state. The martensitic transformation may occurs as a one-step transition from the parent phase to one of martensites (P↔10M, P↔14M or P↔T) or as a multi-step one with the longest sequence: P↔10M↔14M↔T.
Off-stoichiometric NiMnGa alloys, with various chemical compositions, were produced by melt-spinning technique. Transformation behavior was studied by means of differential scanning calorimetery (DSC). Ribbons and bulks reveal reversible martensitic transformation, which occurs in the range of temperatures: between 1000C and -1500C. Transmission electron microscope and X-ray diffractometer were used for structure examination. Dependently on chemical composition five-layered (10M) or seven-layered (14M) martensite was observed, whereas the parent phase shows the B2 structure. Due to high cooling rate realized in melt-spinning technique some amount of amorphous phase was found.
Presentation: Poster at E-MRS Fall Meeting 2007, Symposium E, by Jozef Lelatko
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-10 12:37 Revised: 2009-06-07 00:44