Improved polycrystalline Ni₅₄Mn₁₆Fe₉Ga₂₁ high-temperature shape memory alloy by γ phase distributing along grain boundaries

In this study, the shape recovery and mechanical properties of Ni₅₄Mn₁₆Fe₉Ga₂₁ high-temperature shape memory alloy are improved simultaneously. This results from the low, about 4.4 %, volume fraction of γ phase being almost completely distributed along grain boundaries. The recovery strain gradually increases with the increase in residual strain with a shape recovery rate of above 68 %, up to a maximum value of 5.3%. The compressive fracture strain of Ni₅₄Mn₁₆Fe₉Ga₂₁ alloy is about 35 %. The results further reveal that when applying a high compression deformation two types of cracks form and propagate either within martensite grains (type I) or along the boundaries between martensite phase and c phase (type II) in the present two-phase alloy.