Oscillating laser-arc hybrid welding of aluminum alloy via synchronous wire-powder feeding: Microstructure evolution and mechanical properties

To address the issues of microstructure inhomogeneity and joint softening in oscillating laser‑arc hybrid welding of medium‑thick high‑strength aluminum alloys, a synchronous wire‑powder feeding strategy was introduced. By incorporating Mg powder into the welding process, the energy distribution between the laser and arc was effectively coordinated, resulting in a 19% reduction in the weld transition angle and a 16% decrease in porosity. The addition of Mg powder transformed coarse columnar dendrites in the weld into refined equiaxed grains, significantly enhancing microstructural homogeneity. Furthermore, the weld exhibited a higher density of fine Al2CuMg precipitates, which replaced coarse Al2Cu particles. These microstructural improvements, driven by intensified molten‑pool convection and grain refinement, led to an 18% increase in ultimate tensile strength of welded joint and a remarkable 111% improvement in elongation, accompanied by a more uniform tensile fracture path. The study demonstrates that synchronous wire‑powder feeding combined with beam oscillation is a promising approach for achieving high‑performance welded joints in high‑strength aluminum alloys.