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• Laser oscillation and wire-powder feeding were adopted for laser-arc hybrid welding. • Weld porosity was reduced from 10.7% to 0.7% at oscillating frequency of 250 hz. • The formation of Al2CuMg by substituting Al2Cu eutectic strengthened the weld. • The improvement mechanism of the optimized hybrid welding was summarized. Laser-arc hybrid welding of high-strength aluminum alloy faces the problems of serious evaporation and burning loss of alloying elements, which cause instability on the plasma and melt flow, and reduce weld mechanical properties. In the current study, both high-frequency beam oscillation and synchronous wire-powder feeding were adopted to solve the above problems during the hybrid welding of 8-mm-thick AA2219 aluminum alloy. The results showed that compared with none-oscillating hybrid welding, wire-powder synchronous oscillating hybrid welding reduced weld porosity from 10.7% to 0.7%, and increased the ultimate tensile strength and elongation by 12% and 72% respectively. The feeding of Mg powder promoted the formation of fine Al 2 CuMg strengthening phase by substituting the block Al 2 Cu eutectic. Besides, the oscillating laser at frequency of 250 Hz induced the strengthened stirring of molten pool, which benefited to break and inhibit the growth of dendrite grains, capture bubbles and solidified pores, and reduce the probability of bubble formation due to the instability and collapse of laser keyhole. [Display omitted] [ABSTRACT FROM AUTHOR]

• Beam oscillation was employed for hybrid additive manufacturing of aluminum alloy. • The utilization rate of deposited materials and forming accuracy could be improved. • The tensile properties were increased and the hardness variance was decreased. • The improved mechanisms of beam oscillation on the deposition were concluded. High-frequency circular beam oscillation was employed for the laser-arc hybrid additive manufacturing of AA4047 aluminum alloy. Under the optimized oscillating frequency of 300 Hz, the effects of oscillating diameter (D) on the forming accuracy, microstructure and mechanical properties of deposited thin-walls were studied. It was found that the effective forming width reached a maximum of 88.9 %, and the porosity decreased from 0.1 % to 0.01 % when the D increased from 0 to 1.2 mm. Furthermore, the machining allowance was reduced from 1.51 to 1.25 mm, which indicated that the formation accuracy was improved by 17 %. The increasing D reduced the average size of grains from 55.9 to 44.8 μm, showing a refinement degree of 19.9 %. These improvements reduced the microhardness distribution variance of thin-wall from 31.82 to 13.37. The ultimate tensile strength increased from 219.1 to 227.3 MPa, and the elongation increased from 12.9 % to 14.6 %. Based on the high-speed camera observation, the study discussed the influence of laser beam oscillation on the droplet transfer and melt flow behavior, as well as the improvement mechanism of deposition quality. [ABSTRACT FROM AUTHOR]