Microstructures and mechanical properties of high-strength Mg-Gd-Y-Zn-Zr alloy sheets processed by severe hot rolling

Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy sheets containing long period stacking ordered (LPSO) phase were prepared by hot rolling at 400 °C with total reduction of 96%. Microstructure evolution of the sheets during hot rolling was investigated, and its influence on mechanical properties was discussed. Twinning occurred during the early stage of hot rolling, and disappeared after total reduction higher than 89%. Average grain size was gradually refined, microstructure became much more homogeneous and volume fraction of LPSO phase decreased with increasing rolling reduction. Furthermore, the type of LPSO phases far from and near the block shaped phases were identified to be different. Basal texture was obtained during rolling process, but the intensity declined with the further rolling, which is mainly due to the dynamic recrystallization and the addition of RE elements. The as-rolled sheet with 96% reduction shows excellent mechanical properties: yield strength of 318 MPa, ultimate tensile strength of 403 MPa and elongation to failure of 13.7% at ambient temperature along the rolling direction.