| Summary: | In the present study, the strength and ductility of the as-extruded new alloy are both significantly improved at room temperature by adding 1.2–1.4% elements to the pure Mg. The Mg–0.5Zn–0.2Mn–0.2Sm/0.3La–0.4Ca alloy shows the well ductility with A (elongation) of 27.5–30.5%, and the Mg–0.5Zn–0.2Mn–0.2Sm–0.3La alloy shows the excellent balance of the strength and ductility with Rp0.2 (ultimate tensile strength) of 190 MPa, Rm (high yield strength) of 239 MPa, and A (elongation) of 23.9%. Based on the OM and SEM analysis, grains of the as-cast studied alloys are refined, and the grain refinement is attributed to the Q value of co-additions of Sm, La and Ca, and the segregated Sm/La/Ca atoms at the grain boundaries. According to the EBSD analysis, decreased twins and abundant DRXed grains exist in the as-extruded new alloys via DDRX and PSN mechanisms, as a result, the basal texture is weakened and the SF value is increased. Such microstructures and textures are beneficial to the enhanced strength and ductility of the as-extruded new alloys.
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