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

Abstract

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 287MPa 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.