Multimodal Microstructure Evolution in Wrought Mg-Zn-Y Alloys with High Strength and Increased Ductility

摘要

High strength and ductile Mg_(96)Zn_2Y_2 (at%) alloys with multi-modal microstructure are developed. Microstructure of the extruded Mg_(96)Zn_2Y_2 alloy consists of three regions; the dynamically recrystallized α-Mg fine-grains region, the hot-worked α-Mg coarse-grains region elongated along extrusion direction, and the long-period stacking ordered (LPSO) phase region with kink deformation bands. Bimodal microstructure evolution in α-Mg matrix is influenced by the morphology of the LPSO phase in the as-cast state, therefore, the effect of secondary dendrite arm spacing in cast state on the microstructure evolution and mechanical properties of the extruded Mg-Zn-Y alloy is investigated. An increase in the dynamically recrystallized grains improves ductility of the extruded alloys; the effective dispersion of the LPSO phase enhances strengthening of the alloy.