Effect of rolling passes on the microstructures and mechanical properties of Mg-Gd-Y-Zr alloy sheets

Microstructures and mechanical properties of the pre-extruded Mg-8Gd-3Y-0.4Zr (wt%) alloy in different rolling passes were investigated. The microstructure became homogeneous, which was composed of almost ultrafine dynamically recrystallized grains (6.5 μm) after 5 hot-rolling passes, i.e., total thickness reduction of ~80%. Dynamic precipitation happened in the hot rolling of the alloy and β′ phase precipitates were observed and studied in the peak-aged alloy. With the increase of rolling passes, the equilibrium Mg5(Gd,Y) dynamic precipitates increased while the grain size and the (0002) basal texture followed the opposite trend, and the dynamic precipitation may weaken the ageing precipitation strengthening. The mechanical properties of the as-rolled sample after 5 hot-rolling passes were improved, and the ultimate tensile strength, tensile yield strength and elongation to failure reached 326 MPa, 249 MP and 12%, respectively.