Wide hysteresis NiTi(Nb) shape memory alloys with low Nb content (4.5 at.%)

The microstructure, phase transformation behavior and the effect of predeformation on the hysteresis of NiTi(Nb) (4.5 at.% Nb) shape memory alloys were examined in comparison with the classical Ni47Ti44Nb9 wide hysteresis alloy. It is the Nb dissolved in the NiTi matrix that plays the key role in controlling the martensitic transformation characteristics of NiTi(Nb) shape memory alloys, resulting in the wide hysteresis upon predeformation of the alloys in martensitic state. The isolated β-Nb phase in the matrix contributes little to the hysteresis expansion.