超高温度梯度定向凝固NiMnFeGa磁致形状记忆合金

Crystal growth of magnetic shape memory NiMnFeGa alloy under high temperature gradient unidirectional solidification condition

利用超高温度梯度定向凝固装置制备出定向Ni_(51.2)Mn_(20.0)Fe_(13.0)Ga_(15.8)磁致形状记忆合金。沿晶体生长方向凝固组织由等轴晶逐渐过渡为柱状晶,马氏体变体取向性明显,γ相愈加细小,分布愈加均匀。Ni_(51.2)Mn_(20.0)-Fe_(13.0)Ga_(15.8)合金在加热和冷却过程中发生热致马氏体相变及逆相变,马氏体相变温度M_s=121.3℃,M_f=99.3℃,A_3=118℃,A_f=147℃。

A unidirectionally solidified Ni51.2Mn20.0Fe13.0Ga15.8 polycrystalline rod was prepared under super high temperature gradient unidirectional solidification condition. Solidification microstructures change from equiaxed grains to columnar grains along the crystal growth direction. In unidirectional growth zone, the martensitic variants are parallel to crystal growth direction, and r phase becomes smaller and distributes homogeneously. The Ni51.2Mn20.0Fe13.0Ga15.8 alloy undergoes a reversible thermoelastic martensitic transformation during heating and cooling and the transformation temperatures, M, = 121. 3℃ , M1 = 99. 3℃ , A, = 1181℃ , Af = 147℃ , respectively.