Achieving excellent ductility in high-strength Mg-10.6Gd-2 Ag alloy via equal channel angular pressing

Excellent ductility and high strength were achieved in the Mg-10.6Gd-2Ag (wt. %) alloy via an industrial-scale equal channel angular pressing (ECAP). The ECAP alloy exhibits an extremely high ductility (elongation of 22.6%) as well as a high strength (ultimate tensile strength of 417.2 MPa). This ductility exceeds the known ductility limit of the existing high-strength Mg-RE wrought alloys. After peak-aging, an optimal ultimate tensile strength of 460.3 MPa is obtained accompanied by a moderate ductility (elongation of 8.9%). The excellent ductility originates from the fine and full DRXed microstructure, which involves the homogenous and fine equiaxed grains, the cobblestone-like submicron particles distributed along the α-Mg grain boundaries, and the weak and approximately random texture. The submicron particles are identified as the dynamically precipitated Ag-containing Mg5Gd-typed compound. After peak-aging, co-existence of the high-density basal γ’’ plates and the relatively low-density prismatic β′ plates are observed in the α-Mg grain interior, and an interfacial phase is found to segregate in some α-Mg grain boundaries. The high strength is mainly ascribed to the synergistic effect of the fine grains, the high-frequency high angle boundaries, and the additional co-precipitates of the β′ plates and the γ’’ plates in the aged alloy.