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°C increase for the martensitic transition temperature were observed, further indicating the homogeneity of the composition along the growth axis.