Wire-based friction stir welding enables equal-strength joining of aluminum alloys even with assembling gaps

Insufficient assembly accuracy or material processing errors led to the formation of gaps at the interface, which severely affected joint formation and mechanical properties. Here, wire-based friction stir welding (W-FSW) was proposed to obtain equal-strength joints with different gap widths, whose equipment consisted of a continuous wire-feeding module, a material transporting module and a welding module. 5A06 aluminum alloy plates were welded using Al-Mg alloy wires as the filler materials. Sound joints were obtained through the shear and delivery of filler materials into the assembling gaps. Fine microstructures in the filler material zone were obtained via dynamic recrystallization induced by severe plastic deformation, with an average grain size of 1.38 μm. W-FSW joints with 2-mm-gap width achieved an ultimate tensile strength of 382.0 ± 1.7 MPa (99.1 % of BM) and an elongation of 20.0 ± 0.7 % (91.3 % of BM). The addition of filler materials did not result in strain localization. The W-FSW joints within 2-mm-gap width exhibited equal-strength joints, owing to the absence of thinning and welding defects. As such, W-FSW offered a promising alternative to produce excellent performance joints even with assembling gaps and significantly enhanced the process adaptability of friction stir welding under severe working conditions.