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

Abstract

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.