Deformation behavior and resultant microstructural evolution of Mg-11Gd-1Zn-0.5Sn-0.5Zr alloy containing LPSO phase during hot compression

The flow stress behavior and microstructure evolution of the Mg-11Gd-1Zn-0.5Sn-0.5Zr alloy under thermal compression have been studied in detail. The results show that the flow stress of the alloy decreases with increase in temperature and decrease in strain rate. The activation energy of the alloy was found to be as high as 272.48 kJ/mol by constructing the constitutive equation, which was attributed to the dislocation hindrance of the dense LPSO phase and its kink bands. As the temperature increases, the deformation mechanism gradually shifts from prismatic slip to pyramid slip, and 450 °C is a watershed. Twins and kinks also play an important role in the plastic deformation process. In addition to the particle stimulated nucleation (PSN) mechanism of fragmentary precipitates, dynamic recrystallization (DRX) nucleation can also be stimulated by twins and kink bands due to high stress concentration. However, the large-size and dense lamellar LPSO phase inhibits the nucleation and growth of DRX. When the strain temperature reaches 450 °C or even 500 °C, the LPSO phase in the alloy gradually dissolves into fragments, and the particle stimulated nucleation mechanism promotes the formation of DRX, while reducing the resistance of grain boundary movement to facilitate the growth of DRX.