Improving microstructure and mechanical properties in Mg-6 mass% Zn alloys by combined addition of Ca and Ce

Ca single or Ca-Ce double microalloying Mg-Zn alloy was cast and extruded in the present study. The combined addition of Ca and Ce improved the mechanical properties of Mg-6Zn alloy after extrusion obviously. Microstructure analysis reveals that Ca or Ca-Ce addition refined the dynamic recrystallized (DRXed) microstructure, promoted dynamic precipitation and modified the texture. The fine precipitates in the as-extruded Mg-Zn-Ca-Ce alloy pinned dislocation movement and inhibited dynamic recrystallization, resulting in a bimodal microstructure with fine-grained DRXed region and elongated deformed region. The recrystallization texture was weakened with Ca or Ca-Ce addition, which was mainly attributed to the particle stimulated nucleation (PSN) and shear bands nucleation (SBN). Compared with single Ca microalloying, Ca-Ce double microalloying was more effective to improve the mechanical properties of Mg-6Zn alloy. The as-extruded Mg-6Zn-0.7Ca-0.2Ce (mass%) alloy exhibited a good combination of strength and ductility with the yield strength of 287 MPa and elongation-to-fracture of 16.9%, which was related to the fine DRXed grains with weaker texture, high density precipitates, and the deformed region with strong basal texture.