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