Effect of Metal Mixing on Mechanical Performance of Laser Keyhole Welding of Nickel and Copper

In laser keyhole welding of dissimilar metals, metal mixing in the molten pool is critical to the microstructure and mechanical performance of the welds. In this study, metal mixing and its effects on the mechanical performance of the miscible Nickel-Copper welds are investigated. Experiments were carried out to fabricate samples with different welding parameters. Energy-dispersive X-ray spectroscopy is used to characterize the metal distribution in the fusion zone of the post welds. Mechanical strength testing and fractographic analysis are performed to characterize the strength of the welds and the fracture mode. Two regions of different concentrations can be found in the welds, and the concentrations of these two regions vary significantly with welding parameters. The weld strength is dependent on the interfacial region concentration, and the welds undergo a mixture of shear fracture and tensile fracture during the mechanical strength testing process. The interfacial concentration and the weld strength can be controlled by tuning the concentration of the two concentration regions in the fusion zone and the location of the boundary between the two regions. This study provides insights for industries regarding the design and optimization of the laser welding process to achieve welds with optimal mechanical performance.