Abstract
Welding of aluminum alloys is a crucial manufacturing process to maintain the required in-service properties in transport industries. The commercial 4xxx filler wires provide the joints with relatively low strength. Therefore, to improve the strength of Al joints, it is required to develop new welding filler wires. In this study, the impact of Mg addition (0.6–1%) in two novel filler alloys on the performance and strength of Al joints was investigated. Two commercial 4xxx filler alloys (ER4043 and ER4943) were also selected for comparison. The gas metal arc welding was used to weld the AA6061-T6 thin sheets (2 mm). The microstructure was studied by optical, scanning, and transmission electron microscopies. The mechanical properties were characterized by microhardness and tensile tests. The results show that the microstructure of all joints consists of α-Al, eutectic Si, and Fe intermetallics, while the novel fillers exhibited the stronger precipitation strengthening in the fusion zone relative to the commercial fillers. The microhardness and tensile strength of the samples joined by newly developed fillers were significantly improved compared to that of the commercial fillers, especially in the post-weld-heat-treatment condition. The results were further confirmed by welding high strength AA6011-T6 thick (6 mm) plates.