Effect of pre-strain on the transformation and recovery behaviours of a Ti44Ni47Nb9 shape memory alloy

The recovery strain, stress and transformation temperature of different pre-strained specimens of Ti44Ni47Nb9 were investigated by tensile test and electrical resistance measurement. The results indicated that pre-strain increases the reverse martensitic transformation temperature(A＇s) and hysteresis(As-Ms).The recovery strain and stress are higher if the specimens are pre-strained between Ms and As temperature than outside this temperature range. There exists an optimal pre-strain value, about 10%, at which the specimen exhibits maximum recovery strain and stress.