Dissimilar Laser Joining of NiTi SMA and MP35N Wires

The laser welding of NiTi alloy wire to MP35N wire was investigated to improve the understanding of dissimilar materials joining of NiTi shape memory alloys (SMAs), facilitating their future application in novel devices. Both positioning of the laser beam with respect to the joint’s centerline and laser peak power were found to be critical variables affecting the physical and thermomechanical properties of the welded joint. Positioning of the laser beam was used to control the weld pool composition, while the laser beam intensity affected the pool size and mixing. These variables were shown to greatly affect hardness and susceptibility to cracking in the fusion zone, which heavily impacted the weld strength. With a lower peak power and the laser positioned over the MP35N wire, butt-welded wire joints were achieved with the ultimate load of 66 pct of the NiTi wire breaking load.