Deformation dependence of transformation behavior of Ti-Ni-Nb wide hysteresis shape memory alloy

This work is to systemically study the effect of deformation on the stress-induced martensitic transformation behavior of Ti44Ni47Nb9 alloy by performing differential scanning calorimetry (DSC) and cryogenic tensile tests at a temperature of (M-s+30(degrees)C). DSC measurements showed that the process of stress-induced martensitic transformation had been completed as the specimen was deformed to about 14% of strain in tension. The reverse transformation temperature interval of the stress-induced martensite is much smaller than that of the thermally induced martensite. The experimental results also indicated that A(s) temperature of the reverse transformation, the reverse transformation temperature interval and the transformation heat of the deformed specimen associated with the stress-induced martensite are increased with increasing of the level of deformation. However, the wide hysteresis effect due to the deformation vanished after heating. The transformation heat and the forward transformation start temperature of the subsequent cooling are decreased slightly with increasing of strain.