Effect of pre-strain on shape memory characteristics in a Ti-17Nb-6Zr-1.0at.%O biomedical alloy

The effect of pre-strain on the shape memory characteristics of a biomedical alloy, Ti-17Nb-6Zr-1.0at.%O, was investigated using various tensile tests. A 3% cyclic test on a solution-treated (ST) specimen showed that the critical stress for inducing martensitic transformation (σSIM) decreases with an increase in the number of cycles. From the 9th cycle, the shape perfectly recovers after unloading. In the case of the 4% pre-strained specimen, a 3% cyclic test showed that σSIM dramatically decreases with increase in the number of cycles, and the shape perfectly recovers from 4th cycle. For the 5% pre-strained specimen, 3% and 4% cyclic tests showed superior superelasticity from the 5th cycle. The ST specimen and pre-strained specimens showed similar values of the critical stress for slip and maximum superelastic recovery strain. These results indicate that pre-strain has a small effect on the basic shape memory characteristics of the alloy.