Effect of Y and Ce additions on microstructure and mechanical properties of Mg-Zn-Zr alloys

The effects of trace Y and Ce additions on the microstructure and mechanical properties of extruded Mg-Zn-Zr alloy sheets were investigated. Results indicated that Y and Ce additions led to significant grain refinement and to the formation of Mg-Zn-Ce, Mg3Zn6Y (I-phase) and Mg3Zn3Y2 (W-phase). Mg-Zn-Ce and W-phase were found to possess an orthorhombic and a face centered cubic structure, respectively. Ultimate tensile strength, particularly yield strength, significantly increased after Y and Ce additions, and good elongation was also achieved. The extruded alloy with 0.28 wt% Y and 0.52 wt% Ce exhibited optimal yield strength (313 MPa), ultimate tensile strength (356 MPa) and elongation (12.1%). With increasing Y and Ce additions, strain hardening rate decreased, and the yield-to-ultimate tensile strength ratio (σs/σb) increased. Variations in mechanical properties were discussed based on microstructure observation.