Combined effect of beam oscillation and adjustable ring beam on defect suppression in laser welding of 5A06 aluminum alloy bottom-locking joints

The structural geometry of bottom-locking joints increases the inherent susceptibility to welding defects, particularly spatter and porosity, during laser welding of aluminum alloy, thereby severely compromising joint integrity. In this study, a novel laser welding process integrating beam oscillation with adjustable ring mode (ARM) laser was developed. A defect-free aluminum alloy bottom-locking weld seam with uniform surface finish was obtained. The influence of oscillating-adjustable ring mode (O-ARM) on weld morphology, porosity, process dynamics and mechanical properties was evaluated. Experimental results demonstrate that O-ARM mode markedly improved weld surface quality and suppressed spatter by stabilizing the liquid column. The enhanced molten pool and keyhole stability effectively inhibited porosity formation in O-ARM mode. Consequently, the significant reduction in welding defects led to substantial improvements in mechanical properties. The joint welded with the optimal O-ARM parameters exhibited an average tensile strength of 347 MPa and an elongation of 17.7%, corresponding to 97% and 85.9% of the base metal, respectively. This work demonstrates that O-ARM laser mode is an effective processing strategy for producing high-quality, low-defect aluminum alloy bottom-locking joints.