Dynamic precipitation, dynamic recrystallization behavior, and microstructure evolution of the Mg–8.7Gd–4.18Y–0.42Zr alloy during hot deformation

Mg–8.7Gd–4.18Y–0.42Zr magnesium alloys are subjected to hot compressive tests at a strain rate of 0.002–2 s −1 and a compression temperature of 300–450 °C. Compared with strain rate, compression temperature appears to have a greater impact on dynamic precipitation. By virtue of the pinning effect, precipitates located immediately adjacent to the dynamic recrystallized (DRX) grain boundaries may greatly affect grain growth. As the compression temperature increases, DRX grains multiply rapidly. Nevertheless, the number of DRX grains is decreased owing to the increase in strain rate. However, further increasing the strain rate to 2 s −1 , the increased energy stored generates stronger driving forces, causing dislocations to move, thereby raising the number of DRX grains by a considerable amount. With an increase in compression temperature and a decrease in strain rate, substructure development has been described as high-density dislocation → VLAGBs (sub-GBs) → LAGBs → HAGBs → DRX grains. It is DRX that is responsible for the predominant softening mechanism in this studied alloy, accompanied by a continuous dynamic recrystallization (CDRX) process characterized by transforming low-angle grain boundaries into high-angle grain boundaries, as well as discontinuous dynamic recrystallization (DDRX), which is characterized by bulging grain boundaries. Graphical abstract