Study on the Morphology, Microstructure, and Properties of 6082-T6 Aluminum Alloy Joints in MIG Welding

In this paper, metal inert gas (MIG) welding of 6082-T6 aluminum alloy with a thickness of 4 mm was simulated using a double ellipsoidal heat source. Based on the simulation results, the evolution of the microstructure, the strengthening mechanism of mechanical properties, and the corrosion characteristics of the welded joint were studied further. The thermal cycle curve of the welded joint was obtained through numerical simulation. When the heat input was 2.34-2.75 KJ/mm, the temperature of the welded joint reached the melting point of the material. With the increase in welding heat input, the weld metal (WM) organization changed from the dendrite to the cellular crystal transformation and presented a uniform distribution. The precipitation of the strengthened phase was inhibited at 2.75 KJ/mm. When the heat input changed from small to large, the tensile strength and toughness first increased and then weakened. Dimple distribution of tensile fractures was observed with a scanning electron microscope. When the welding heat input was 2.57 KJ/mm, the mechanical properties of the joint were the best. The tensile strength can reach 76.62% of the base material, and the elongation after breaking can reach 59.38% of the base material. However, it was concluded through studying electrochemical corrosion that the corrosion resistance of welded joints under this parameter was the worst. This may be caused by the presence of Cu, Fe, Si, Mg, and other compounds, and was proven to be Mg2Si through EDS analysis.