The suppression mechanism of keyhole-induced porosity of oscillating laser beam welding (OLBW) was investigated via numerical simulation with keyhole dynamics and melt flow. The established model was verified by the corresponding experimental results. Results show that the weld porosity of 304 stainless steel can be controlled within 0.6% in OLBW and the large keyhole and well-balanced energy of the melt pool are contributing to porosity reduction. Also, two kinds of porosity suppression mechanisms in OLBW were clarified: first, the stirring effect of the oscillating beam keeps the bubble migration speed is superior in the competition with the solidification rate; second, bubbles can be absorbed timely by the dynamic keyhole when the moving speed of the keyhole reaches 504.6 mm s −1 .

Al/steel butt-joints are hard to be fusion welded because of the easily formed and unevenly distributed brittle intermetallic compounds (IMCs) at the interface. Laser-arc hybrid welding was used to suppress the IMCs formation and improve its uniformity through beam oscillation. The weld defects of uneven formation and lack of fusion were suppressed at optimised frequency of 150 Hz. Furthermore, the interface was transferred from an uneven two-layer IMCs ( ≥ 3.8 µm), including Al 5 Fe 2 and Al1 3 Fe 4, to a uniform single-layer Al 5 Fe 2 ( ≤ 1.4 µm). Owing to these changes, not only the tensile property was increased by 65% compared to non-oscillating weld, but also the bending property that hardly reported in most studies was enhanced by 96%.

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