Effect of various Ca content on microstructure and fracture toughness of extruded Mg-2Zn alloys

Abstract

Effect of various Ca content on microstructure and fracture toughness of extruded Mg-2Zn was investigated in this paper. The experimental results show that Ca addition (0.2 wt% Ca, 0.5 wt% Ca) gradually refines the recrystallized grains of Mg-2Zn, changes the type, size and distribution of precipitates in Mg-2Zn and also strengthens their (0002) textures. On the other hand, as Ca content increases, the yield and tensile strength of Mg-2Zn gradually increases but their total elongation decreases. Moreover, the plane strain fracture toughness (evaluated by KIC value) of extruded Mg-2Zn is improved and ductile fracturing gradually becomes dominant with increasing Ca addition. The grain refinement of Mg-2Zn with increasing Ca addition is mainly attributed to the restraining effect of Ca-containing precipitates on the growth of the dynamic recrystallized (DRXed) grains during extrusion process. And the enhancement of fracture toughness of extruded Mg-2Zn due to Ca addition mainly results from the grain refinement effect which activates the non-basal slip and decreases the fraction of deformation twins.