Improvement of microstructure and mechanical properties of AZ61 Mg alloys subjected to rapid cooling friction stir welding

Abstract

Conventional friction stir welding (FSW) AZ61 Mg alloy weld usually exhibits an Al supersaturated α-Mg solid solution with an intense basal texture, resulting in an unsatisfactory strength and ductility. In this work, rapid cooling FSW was conducted on the AZ61 Mg alloy to improve the microstructure and mechanical properties of the weld. A fine grain structure with dislocations, β-Mg₁₇Al₁₂ particles, and {10-12} twins was obtained in the weld. Additionally, the particle stimulated nucleation induced dynamic recrystallisation and {10-12} twinning induced dynamic recrystallisation contribute to the reduction of the basal texture intensity. The mechanical properties of the weld were improved due to the synergistic effects of the dislocations, β-Mg₁₇Al₁₂ particles, and {10-12} twins.