The effect of Y addition on recrystallization and mechanical properties of Mg-6Zn-xY-0.5Ce-0.4Zr alloys

Microstructure and mechanical properties of extruded Mg-6Zn-xY-0.5Ce-0.4Zr sheets were systematically investigated. Mg-Zn-Ce, I-phase (Mg3Zn6Y) and W-phase (Mg3Zn3Y2) with different morphologies were observed in as-cast and extruded conditions. Numerous nano-precipitates were found along grain boundaries and inside grains in both dynamically recrystallized (DRXed) and unDRXed regions after hot extrusion. The area fraction of DRXed regions increases with Y additions mainly due to particle stimulated nucleation (PSN). An extruded fiber texture was observed after hot extrusion. The texture is strengthened firstly and then weakened. The extruded alloys with 0.5-1 wt% Y and 0.5 wt% Ce exhibit much better mechanical properties compared with other Mg alloys such as Mg-5Zn-1Y-1Zr (wt.%) and Mg-6Zn-1Ce-0.5Zr (wt.%) alloys under the same extrusion ratio. The extruded alloy with 0.2 wt% Y and 0.5 wt% Ce has the yield strength of 322 MPa, ultimate tensile strength of 378 MPa and elongation of 8.6%, which is the highest value among the studied alloys. Grain boundary strengthening and precipitation strengthening are the two most important factors for improving yield strength of Mg-6Zn-xY-0.5Ce-0.4Zr alloys. The addition of Y is an effective way in significantly improving the mechanical properties of Mg-6Zn-xY-0.5Ce-0.4Zr alloys.