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 γ phase (type II) in the present two-phase alloy.