Enhanced strength and ductility of friction-stir-processed Mg–6Zn alloys via Y and Zr co-alloying

Friction stir processing (FSP) was utilized to fabricate high strength and ductility Mg–6Zn alloys via the co-alloying of 1.0 Y and 0.5 Zr elements. The effect of co-alloying on microstructure and mechanical properties of the as-casted and FSPed Mg alloys were evaluated. Grain refinement and second-phase increase via co-alloying were obtained. The increased second-phases contributed to dynamic recrystallization and weakened the basal texture through heterogeneous nucleation. The yield strength, ultimate tensile strength and elongation of the FSPed Mg–6Zn–1Y-0.5Zr alloys reached 170 MPa, 310 MPa and 27.7%, which enhanced by 27.8%, 10.7% and 48.9% than the FSPed Mg–6Zn alloys. Grain refinement, dispersion strengthening and the tailored texture are responsible for the enhancement of mechanical properties. The Mg–Zn series alloys with trace Y and Zr co-addition are confirmed to be promising for developing rare-earth containing Mg alloys with outstanding mechanical performance and acceptable cost.