Microstructure, magneto-structural transformations and mechanical properties of Ni50Mn37.5Sn12.5-xInx (x=0, 2, 4, 6 % at.) metamagnetic shape memory alloys sintered by vacuum hot pressing

Structural, magnetic and mechanical properties of Ni50Mn37.5Sn12.5-xInx (x = 0, 2, 4, 6% at.) alloys sintered by vacuum hot pressing were investigated. The porosity of sintered alloys increases with increasing of In concentration. The addition of In leads TCA to decrease while Ms is shifted to higher temperatures. Annealing sintered samples at 1020 K for 24 h allowed for lowering of the thermal hysteresis and narrows the temperature range of the forward and reverse martensitic transformations. Ternary Ni-Mn-Sn alloy exhibits the best mechanical properties and it can be plastically deformed up to about 5% while maintaining about 2000 MPa strength. TEM observations revealed unique microstructure observed in the case of polycrystalline Heusler alloys consisting of equiaxed grains of martensite and austenite with size of about 2 μm.