Impact of laser oscillation on molten pool dynamics in narrow-gap welding of 5A06 aluminum alloy

An integrated approach of online monitoring and numerical simulation was employed to systematically analyze plume-induced energy attenuation and molten pool properties in narrow gap laser welding (NGLW) of 18 mm 5A06 plates, focusing on different laser beam oscillation patterns to enhance weld formation quality. Compared to laser welding without oscillation, circular oscillation was demonstrated to enhance molten pool and plume stability, reduce plume height and mitigate laser energy attenuation induced by the plume. Simulation results revealed that in NGLW without oscillation, the molten pool front exhibited flow patterns from both sidewalls toward the center due to lateral constraints, thereby destabilizing the molten pool. In contrast, the stirring effect generated by circular oscillation eliminated such constraints. It redirected the molten flow from the center toward the groove sidewalls, enhancing interfacial bonding between the filler material and sidewalls. Within a groove width range of 3–6 mm, welds free from lack-of-fusion (LOF) defects were consistently achieved when the laser amplitude was set at 2.4 mm.