Multi-objective optimization of laser-welded joints between AZ31B and fabricated nylon 66 composite sheets

This study investigates the overlapped laser welding of AZ31B magnesium alloy and graphene oxide (GO)-reinforced Nylon 66 composites. The research emphasizes the quantitative assessment of weld morphology, interface of bonding mechanisms, and the modes of failure. Utilizing a pseudo-pulsed fiber laser operating in continuous mode, factors such as laser power, welding speed, and spot diameter were optimized. Quantitative analysis showed distinct weld regions, including elongated fibrils and polymer micro-voids. Bonding occurred mainly through melting–reflow and mechanical interlocking. Controlled thermal gradients minimized polymer degradation, while high-purity argon shielding prevented oxidation and improved weld quality. Tensile tests post-welding indicated ultimate tensile strength (UTS) values ranging from 32-34 MPa, reflecting the effectiveness of the optimized parameters. Response Surface Methodology (RSM) was employed to develop mathematical models correlating input parameters to output properties, facilitating a multi-objective optimization strategy incorporating NSGA-II and TOPSIS. This approach predicted an optimal combination of approximately 512.70 W laser power, 574.39 mm/min welding speed, and a 1.5 mm spot diameter, achieving mean absolute errors of 3.37% for modulus and 1.7% for UTS in confirmation tests. This integrated methodology significantly enhances weld quality and provides valuable insights for developing high-performance joints in advanced engineering applications.