Mechanical properties of Mg-8Gd-3Y-0.5Zr alloy with bimodal grain size distributions

The Mg-Gd-Y-Zn-Zr alloys are representational and potential age-hardening systems as reported in the past ten years, but their mechanical properties are still dependent on the grain size and its distribution. The effect of bimodal structure on mechanical properties of Mg-8Gd-3Y-0.5Zr alloy with bimodal grain size distributions was investigated. The results suggested that the volume fraction of fine grain (FG) and coarse grain (CG) could be controlled by combined processes of hot forging, extrusion and annealing. And for the present alloys with bimodal grain size distribution, the improvement of strength is still attributed to the grain refinement. The morphology of bimodal grain size distribution has a marked impact on the ductility of the alloy, i.e. with the increase of coarse grain volume fraction, the elongation to failure increases at the beginning and then decreases. The mechanism of the toughening effect of bimodal grain size distribution on the Mg-Gd-Y-Zn-Zr alloys with bimodal grain size structure has been discussed.