Microstructural evolution and enhanced mechanical properties of Mg–Gd–Y–Zn–Zr alloy via centrifugal casting, ring-rolling and aging

Abstract

<p>A ring-shaped Mg–8.5Gd–4Y–1Zn–0.4Zr (wt%) alloy was manufactured via centrifugal casting and ring-rolling process. The effects of accumulative ring-rolling reduction amount on the microstructure, texture, and <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/materials-science/tensile-property" target="_blank">tensile properties</a> of the alloy were investigated. The results indicate that the microstructure of centrifugal <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/materials-science/cast-alloy" target="_blank">cast alloy</a> consists of equiaxed grains and network-like eutectic structure present at grain boundaries. The ring-rolled alloy exhibits a characteristic bimodal microstructure composed of fine dynamic recrystallized (DRXed) grains with weak basal texture and coarse un-DRXed grains with strong basal texture, along with the presence of LPSO phase. With increasing amount of accumulative ring-rolling reduction, the coarse un-DRXed grains are refined via the formation of increasing amount of fine DRXed grains. Meanwhile, the dynamic precipitation of Mg5RE phase occurs, generating a dispersion strengthening effect. A superior combination of <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/materials-science/mechanical-strength" target="_blank">strength</a> and ductility is achieved in the ring-rolled alloy after an accumulative rolling reduction of 80%. The <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/materials-science/ultimate-tensile-strength" target="_blank">tensile strength</a> of this ring-rolled alloy after peak aging is further enhanced, reaching 511 MPa, while keeping a reasonable ductility. The salient strengthening mechanisms identified include the grain boundary strengthening of fine DRXed grains, dispersion strengthening of dynamic precipitated Mg5RE phase, short fiber strengthening of LPSO lamellae/rods, and precipitation strengthening of nano-sized prismatic β′ precipitates and basal γ′ precipitates.</p>