A preliminary study on the mechanism of preparing high strength extruded Mg-Gd-Y-Zn-Mn alloys through pre-stretching and ageing

This work investigated the mechanism of preparing high strength extruded Mg-Gd-Y-Zn-Mn alloys through pre-stretching and ageing. A high strength alloy of Mg-10.21Gd-4.45Y-1.45Zn-2.21Mn (wt%) with a yield strength (YS) of 429 MPa and an ultimate tensile strength (UTS) of 492 MPa was obtained. The cold deformation by pre-stretching and the precipitation of the strengthening phases after ageing together contributed to the high strength. The γ″ phase was found in the pre-stretched alloy after extrusion, providing strong evidence that deformation facilitates the formation of the γ″ phase in the alloy where more than 2 wt% Mn was added. Compared with the sample subjected to ageing after extrusion, the grain boundary strengthening contributes most to the yield strength increase of the sample subjected to pre-stretching and ageing after extrusion.