Porous Nimnga Shape Memory Alloys with Large Superelasticity

Ni50Mn28Ga22 alloy with porous structure was prepared by powder metallurgy with NaCl as pore forming agent. The porous structure reduces the limit of grain boundary on martensite transformation, thus improving the superelasticity of polycrystalline samples. The stress-strain curve has obvious multistage platforms, which shows that the porous alloy has a multi-step transformation process in the process of stress. Even after multiple compression recoveries, there is no crack or superelasticity weakening. Another advantage is that open pores have a high specific surface area, and a large number of through-holes allow fluid infiltration, which improves the heat exchange efficiency. Therefore, porous NiMnGa alloy is one of the candidates for magnetic refrigeration materials.