Effect of Zn Addition on Microstructure and Mechanical Properties after Extrusion, Rolling and Ageing in Mg-9Gd-3Y-0.5Zr Alloys

Evolution of microstructure and mechanical properties of the Mg-9Gd-3Y-0.5Zr base alloys without 0.5% Zn addition (GWK930) and with Zn addition (GWZK9300) have been investigated during processing by extrusion, rolling and ageing. It was found that the yield/ultimate strength of the two as-rolled alloys increased with the rolling strains. Twinning was the main deformation mechanism in GWK930 alloy while few twinning could be detected in the GWZK9300 alloy due to the dense secondary phases such as LPSO structure. The (0002) texture intensity in two as-rolled alloys increased with the rolling reduction, however, a typical rolling basal plane texture with single peak was found in GWZK9300 while a bimodal texture was found in the GWK930 alloy. Compared with GWK930 alloy, GWZK9300 alloy exhibited higher strength and ductility after rolling, annealing and ageing treatments. The finer grain size was due to more recrystallization fraction, while more fine secondary phases dispersed in matrix. And the basal texture strengthening after rolling deformation and subsequent heat treatment are suggested to be responsible for the superior comprehensive mechanical properties of GWZK9300 alloy.