Mechanical and Magnetic Properties of Porous Ni₅₀Mn₂₈Ga₂₂ Shape Memory Alloy

A porous Ni50Mn28Ga22 alloy was produced using powder metallurgy, with NaCl serving as the pore-forming agent. The phase structure, mechanical properties, and magnetic properties of annealed bulk alloys and porous alloys with different pore sizes were analyzed. Vacuum sintering for mixed green billets in a tube furnace was employed, which facilitated the direct evaporation of NaCl, resulting in the formation of porous alloys characterized by a complete sinter neck, uniform pore distribution, and consistent pore size. The study found that porous alloys within this size range exhibit a recoverable shape memory performance of 3.5%, as well as a notable decrease in the critical stress required for martensitic twin shear when compared to that of bulk alloys. Additionally, porous alloys demonstrated a 2% superelastic strain when exposed to 353 K. Notably, under a 1.5 T magnetic field, the porous Ni50Mn28Ga22 alloy with a pore size ranging from 20 to 30 μm exhibited a peak saturation magnetization of 62.60 emu/g and a maximum magnetic entropy of 1.93 J/kg·K.