Effect of welding modes on mechanical properties and microstructure of dissimilar NiTi-PtIr joints produced by laser welding

• Nd:YAG laser welding performed between NiTi tubes and PtIr wires using high as well as low power modes. • Single sided weld with high laser power leads to high Ni vaporisation and high Pt concentration in the fusion zone. • Double sided weld with low laser power gives higher Ni retention, lower Pt concentration, and equiaxed microstructure. • Double sided weld exhibits higher tensile strength and significantly enhanced ductility compared to single sided weld. Dissimilar joining of NiTi and PtIr presents a unique challenge due to their compositional differences and properties disparities, requiring controlled fusion zone (FZ) composition for mechanical reliability. In the present work, single-sided and double-sided laser welding modes were employed to join NiTi tube with PtIr wire. The double-sided weld exhibited higher tensile strength and significantly enhanced ductility than the single-sided weld because of higher Ni retention, lower Pt concentration, and formation of equiaxed microstructure in the FZ. This study establishes that double-sided, low-power laser welding mode exhibits a more effective strategy for joining NiTi-PtIr joints with improved mechanical performance.