Microstructures and mechanical properties of laser-arc hybrid welded high-strength aluminum alloy through beam oscillation

High-frequency beam oscillation and synchronous wire-powder feeding were adopted for the laser-arc hybrid welding of a 2219-T6 high-strength aluminum alloy. Increasing the beam oscillation frequency from 0 to 250 Hz not only reduced the weld porosity from 2.64% to 0.16% but also promoted the transformation of columnar dendrites to fine equiaxed grains. In addition, the content of precipitated Al2CuMg increased with the refined size of the weld microstructure. The length of the columnar grains and the diameter of the equiaxed grains in the weld center were reduced by 40% and 50%, respectively. Owing to these improvements, the weld microhardness increased and became more uniform, and the variance decreased by 74%. The ultimate tensile strength and elongation of the welded joint reached 238.5 MPa and 4.3%, respectively, which were 26.5% and 105% higher than those of the non-oscillating hybrid weld, respectively. The weld tensile strength and the proportion of the area of the pore were negatively correlated. The porosity and microcracks of the welded joints were the main factors affecting the tensile strength of welded joints.