Influence of minor Ce additions on the microstructure and mechanical properties of Mg-1.0Sn-0.6Ca alloy

The microstructure and mechanical properties of Mg-Sn-Ca-Ce alloys with different Ce contents (0.0, 0.2, 0.5, 1.0 wt%) were studied at room temperature. Ce additions to ternary Mg-Sn-Ca alloy resulted in grain refinement as well as a change in the category of second phase from CaMgSn to (Ca, Ce)MgSn and Mg12Ce. The volume fraction of second phase increased with rising Ce content, which aggravated the restriction of DRXed grain growth during the extrusion process and eventually led to texture weakening of as-extruded Mg-Sn-Ca based alloys. In terms of plasticity, owing to vigorously activated basal slip and homogeneous distributed tensile strain in tension, the tensile ductility of as-extruded alloys reached the maximum value of 27.6% after adding 0.2 wt% Ce, which enhanced by about 26% than that of ternary Mg-Sn-Ca alloy. However, further Ce additions (0.5 and 1.0 wt%) would coarsen the second phase particles and then impair ductility. The tension-compression yield asymmetry of as-extruded Mg-Sn-Ca ternary alloy was alleviated greatly via Ce additions, due to the joint effects of grain refinement, increased amount of strip distributed second phase particles and texture weakening.