Effects of process parameters on microstructure and properties of welded joints with oscillating laser-CMT hybrid welding of die-cast aluminum/AA6061 aluminum alloy

Abstract To address the technical challenges of joining die-cast aluminum and AA6061 aluminum alloy in automotive lightweight manufacturing, this study adopted oscillating laser-arc (CMT + Pulse) hybrid welding technology. Through metallographic observation, mechanical property testing, and high-speed photography, the effects of key process parameters (laser power, oscillation diameter/frequency, and joint configuration) on weld formation, microstructure, mechanical properties, and porosity distribution were systematically investigated. The results indicate that the lap joint exhibits better weld quality and lower porosity compared with the full lap joint, with the optimal parameters being a laser power of 4500 W, an oscillation radius of 0.1 mm, and an oscillation frequency of 200 Hz. This is attributed to the fact that the plasma generated by the oscillating laser merges with the arc plasma, thereby stabilizing the arc and preventing arc interruption during high-speed welding. Compared with the base metal, the tensile strength of the welded joints decreases by approximately 20%, and microhardness reduction mainly occurs in the arc zone and the adjacent heat-affected zone. The joint performance is superior to that of conventional arc welding and comparable to that of pure laser welding. The synergistic effect of laser oscillation and pulse arc significantly suppresses porosity formation, reducing it to nearly zero under optimal parameters. Process-induced pores are the primary factor impairing joint performance, as their irregular morphology readily induces stress concentration and crack initiation. High-speed photography reveals that the plasma generated by the oscillating laser stabilizes and guides the arc, ensuring continuous arc operation during high-speed welding. This study verifies the feasibility and reliability of oscillating laser-C + P hybrid welding for dissimilar aluminum alloys, providing technical support for high-efficiency and high-quality welding in automotive lightweight applications.