A novel method for simultaneously improving the strength and ductility of AZ31 friction stir welded joint

In this study, a novel localized selective remelting technique was proposed to treat the welding interface regions on the top and bottom surfaces of the AZ31 friction stir welded joint. Compared with the untreated joint, the treated joint achieved a favorable combination of strength (ultimate tensile strength of 238 MPa) and ductility (elongation of 13.3%). Digital image correlation (DIC) characterization revealed that the high strain-hardening ability primarily stemmed from the substantial mitigation of strain localization, which was caused by a comprehensive factor, including reduced SF value fluctuation between weld micro-zones, low residual dislocation density, and numerous extension twinning activation in the nugget zone.