Static recrystallization and precipitation behavior of forged and annealed Mg–8.7Gd–4.18Y–0.42Zr magnesium alloy

A study of the static recrystallization and precipitation behavior of a forged Mg–8.7Gd–4.18Y–0.42Zr alloy after annealing at 250–400 ℃ was conducted using OM, SEM, TEM, and EBSD methods. Forging results in a substantial number of coarse grains with parallel and intersecting twins throughout the microstructure, but there are also a few smaller grains containing only parallel twins. As the annealing progresses, the twins promoted a continuous static recrystallization (SRX) behavior. The intersected extension twins were less stable in coarse grains compared to parallel twins and more conducive to providing nucleation sites for static recrystallization. A complete static recrystallization microstructure shows an average grain size of 18.32 µm after annealing at 350 °C and holding for 120 min. Precipitation distributed along twin and grain boundaries and occurred concurrently with static recrystallization. As a result, recrystallized grains are impeded in their growth due to pinned grain boundaries. Furthermore, a weaker basal texture was observed after subsequent annealing due to the random orientations of static recrystallization fine grains. The results demonstrate that homogeneous grain refinement after subsequent annealing can be achieved by developing twin structures during forged deformation.