The solid-liquid interface morphology of the unidirectionally solidified Ni2MnGa magnetic shape memory alloy

The crystals of Ni2MnGa were prepared by high temperature gradient zone-melting unidirectional solidification. Through altering the growth velocity, the temperature gradient and the zone-melting length, a flat solid-liquid interface can be obtained, and a single crystal was successfully prepared. The crystal growth competition was observed in Ni50Mn29Ga21 alloy. No obvious composition macro-segregation was detected. In X-ray diffraction pattern only 400 and 004 peaks of the tetragonal martensitic structure appear, showing the preferred orientation along <100> of the high-temperature cubic austenite Ni2MnGa. DSC and TG methods were applied to describe the distributions of the martensitic transition temperature and Curie temperature along the solidified axis of the Ni50Mn29Ga21, no obvious change for Curie temperature and about 10 degreesC increase for the martensitic transition temperature were observed, further indicating the homogeneity of the composition along the growth axis.