Influence of localized selective remelting positions on mechanical properties and deformation behavior of friction stir welding AZ31 Mg joint

In this work, selective tungsten inert gas (TIG) arc remelting was applied to the nugget zone (NZ) side or NZ middle of a friction stir welding (FSW) AZ31 Magnesium joint, with the aim to explore the impacts of localized remelting positions on microstructure and mechanical properties, as well as to uncover the relationship between mechanical behavior and microstructure of the joints. It was found that the TIG arc treatment contributed to a random texture distribution within the TIG melting zone and a reduction of residual dislocations in the microstructure. The resultant mechanical properties were significantly enhanced, particularly elongation (EL) and ultimate tensile strength (UTS). Notably, remelting at NZ side yielded superior properties compared to the NZ middle, with UTS and EL increasing from 5.5 % to 201 MPa in the initial joint to 13.3 % and 238 MPa, representing an increase of 18.4 % and 123 %, respectively. The improved mechanical properties were primarily related to the weakened strain localization.