Influence of stresses on martensitic transformation in ferromagnetic shape memory Ni50Mn19Fe6Ga25 ribbons
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The influence of stresses on martensitic transformation in Ni50Mn19Fe6Ga25 melt-spun ribbons was studied. X-ray diffraction examination shows that the ribbon has a pure cubic L21 phase at room temperature and that the ribbon surface exhibits  preferentially oriented texture, while the  axis is about 45° tilted from the normal of the ribbon. By calculating the d spacing at different angles with the length direction of the ribbon, the tension was observed. It was found that the direction of the stress was along  direction of the oriented textured grains. During cooling, there is no obvious structural transition observed in as-spun ribbons. However, when the ribbons were annealed at 900 K for 24 h, the tension along  direction disappeared and the structural transition from cubic to tetragonal occurred obviously during cooling. It indicates that it is the tension along  direction to suppress the martensitic transformation in the as-spun ribbons.
Keywordsstress martensitic transformation ferromagnetic shape memory alloy
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