Effect of post-weld-annealing on the tensile deformation characteristics of laser-welded NiTi thin foil

Laser welding is an important process for fabricating complex components involving NiTi shape memory alloy. As welding is a thermal process, the amount of heat input and the rate of cooling have significant impact on the microstructure and hence the resultant characteristics of NiTi. In this study, the effect of laser welding and post-weld-annealing from 573 K to 1173 K on the thermal phase transformation behaviors, tensile deformation and micro-hardness characteristics of the laser-welded NiTi thin foils were investigated. It was found that the as-welded sample exhibited inferior super-elasticity compared to the base material, and the super-elasticity could be partially restored by annealing at 573 K. On the other hand, annealing of the weldment above the recrystallization temperature would lower the super-elasticity.