Effect of the welding direction on the microstructural characterization in fiber laser-GMAW hybrid welding of 5083 aluminum alloy

Thick plates of 5083 aluminum alloy are welded with double-side hybrid welding method, and the effects of different heat source positioning arrangement on porosity formation, microstructure and mechanical property of the welding joints are studied. The results show that relative stable arc and stable process can be obtained in laser-arc hybrid welding (LAHW) process, and the weld bead with lower porosity level can be achieved. Fewer air involved in the weld pool, better stability of the keyhole and the easier escape of bubbles from the weld pool are the three ways to suppress the porosity. In both arc-laser hybrid welding (ALHW) and LAHW processes, the columnar grains are found in the fusion boundary, while equiaxed grains are observed in the weld center. In LAHW process, although the grain size is larger, the strength of the joint is higher, which is attributed to less porosity formation, the slight loss of Mg, more second-phase particles with uniform distribution, and the formation of dislocation with higher density in the joints.