Microstructure and enhanced mechanical performances of dissimilar Mg alloys fabricated by pulse current-assisted friction stir welding (PCaFSW)

Abstract

The dissimilar AZ31B/AZ61 Mg alloy joints were fabricated by pulse current-assisted friction stir welding (PCaFSW). The maximum tensile strength and elongation were 314.28 MPa and 13.66%, respectively. A micro interlocking structure was formed and the grain refinement effect was enhanced by the PCaFSW process, which was improved relative to that in the conventional FSW. The enhanced strength and plasticity with increasing pulse current were attributable to the grain refinement, weakening of texture strength, formation of nano-scale precipitates and increase of short dislocation lines. The fracture mode was transformed from a brittle fracture mode to a combined fracture mode of brittle and ductile fractures.