Combined Effect of Annealing Temperature and Pre-deformation on the Superelastic Behaviors of NiTi Shape Memory Alloys

The combined effect of annealing temperature and pre-deformation on the superelastic behaviors of NiTi shape memory alloy wires was investigated by testing two types of samples with 72 and 35% area reduction. It is found that the annealed samples with 72% area reduction exhibited larger martensitic transformation stress, and the annealed samples with 35% area reduction exhibited superior superelastic cycle stability. The stress hysteresis of martensitic transformation for both two types of samples decreased with decreasing annealing temperature. In addition, pre-deformation enhanced the superelastic cycle stability and increased the stress hysteresis of the NiTi wires with 72% area reduction, but it had little effect on the stress hysteresis of the NiTi wires with 35% area reduction.