In laser-arc hybrid additive manufacturing (LAHAM), the high-power laser required for precise forming often leads to unstable keyhole behavior and severe keyhole-induced porosity, which compromise mechanical properties. In this study, laser beam oscillation was employed to address this contradiction. It was found that laser beam oscillation could distribute the laser energy over a larger area, reducing the average power density below the critical threshold for keyhole formation. Under high-power laser processing (laser power of 3 kW), optimizing the oscillation parameters decreased the keyhole-induced porosity from 16.3 % under the non-oscillating condition to 0.3 %, and restored the elongation from 2.2 % to 17.4 %. Moreover, the high-power laser with beam oscillation preserved the precision-forming benefits. The highly ionized plasma generated by the laser provided a low-resistance channel for the arc current, which attracted and compressed the arc. The resulting electromagnetic forces guided the droplets along a more controlled transfer path, and together with the stabilized molten pool behavior, enabled superior forming accuracy. Compared with the low-power (laser power of 1 kW) samples, the surface roughness was reduced by 68.2 %, and the material utilization increased by 29.4 %. In addition, the high-power oscillating laser promoted molten flow to disrupt dendrites, facilitated rapid crystallization, and reduced local temperature gradients, thereby breaking the directional growth of columnar grains. The resulting refined, random-oriented multimodal grain structure significantly reduced mechanical anisotropy. This work provides a feasible technical pathway and a valuable reference for achieving high-quality additive manufacturing of aluminum and other challenging materials.
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