Study on weld formation and microstructure of A7N01 aluminum alloy by hybrid laser-MIG welding

In order to study the effect of process parameters on weld formation, microstructure characteristics, and properties of the joint welded by laser-melt inert-gas (MIG) hybrid welding, laser-MIG hybrid welding of 6mm A7N01 aluminum alloy plates was carried out with different laser powers, welding speeds, and groove forms. The microstructure and properties of the joints were observed and tested. The results show that as the laser power increases, the weld penetration increases linearly. Furthermore, the higher the welding speed, the smaller the weld width and the penetration depth, and the margin is slightly increased. The welded joints have good adaptability to different groove forms. When the hybrid laser-MIG welding was carried out with the laser power of 3.0kW, welding speed of 1.0m/min, and the Y-shaped 30° groove, the sound joint was obtained. The average tensile strength of the joint is 271MPa, which is 60% of the base metal. The center hardness of the weld is 85.4HV, which is 78% of the base metal. In the joint, the grain in the heat-affected zone is coarsened, the hardness is reduced, and the grain in the fusion zone is dendritic grain, which is easy to produce hydrogen holes in the process. In addition, the grain is equiaxed at the center of weld. This research is conductive to obtaining a well-formed laser-MIG hybrid welding joint of A7N01 aluminum alloy. In addition, the grain is equiaxed at the center of weld.