Simultaneously Improving Strength and Ductility of Mg-3Li-8Gd-2Y-1.5Ag Alloy by Solution Treatment and Hot-Rolling Process

The microstructure and mechanical properties of Mg-3Li-8Gd-2Y-1.5Ag (wt%) alloy at as-cast state, as-solution state, and as-rolled state (three rolling reductions of 30, 50, and 70%) are investigated. With the increase in solution time at 520 degrees C, the dissolution of Mg-24(Gd,Y)(5) phase along the grain boundaries and the coarsening of grain size occur. The solution parameters of 520 degrees C/4 h are chosen in combination with microstructural evolution, grain size, and microhardness. The dynamic precipitation of irregular spherical-like beta(1), needle-like beta ', fine beta, and twins is observed after 30% hot rolling at 450 degrees C. With increasing the reduction to 70%, the number of beta(1), beta ', and twins increases and massive stacking faults (SFs) appear in the twins. The strength and ductility of Mg-3Li-8Gd-2Y-1.5Ag alloy are simultaneously improved by the combination of solution treatment and hot-rolling process due to the precipitation strengthening of beta(1) and beta ', the formation of twins and SFs, and the fragmentation of Mg-24(Gd,Y)(5) phase along the grain boundaries.