Mechanical performances and corrosion behaviors of robotic wire-feeding friction stir welding of 5A06 aluminum alloys

Large gap width easily occurs in large and complex structural welds due to joint configurations and profile straightness tolerances, which is extremely unfavorable to the joint forming and performance. A novel method, named robotic wire-feeding friction stir welding, was proposed for welding large-gap-width joints. 3-mm-thick 5A06 aluminum alloy plates with a gap width of 2 mm were welded. The results showed that sound joints were obtained and the filler materials achieved a high-quality metallurgical welding with the plates. The ultimate tensile strength of the joints reached 388.9 MPa ± 1.4 MPa, which is 99% of the base material. The adverse effects of gap on welding quality were eliminated. Fine microstructures were obtained via dynamic recrystallization induced by severe plastic deformation. In the salt spray corrosion test, the fine and homogeneous second phase particles in the weld nugget zone and filler material zone made their corrosion resistance better than that of the heat-affected zone and the BM. The filler material enhanced the corrosion resistance of the weld nugget zone. Pitting occurred on the surface of the heat-affected zone which became the crack initiation position. The ultimate tensile strength of the joints reduced to 356.6 MPa ± 1.2 MPa, reaching 91% of the BM.