Hot Compressive Deformation Behavior and Microstructure of LZ31 Magnesium–Lithium Alloy

To obtain the best hot deformation parameters of magnesium–lithium alloy and to provide the evidence for formulating hot deformation process, the deformation behavior of LZ31 magnesium–lithium alloy under hot compression was studied firstly. Then, the constitutive equation was established and the related microstructure evolution in deformation process was investigated. The results show that the alloy appears hardening and softening during the hot deformation process. After the flow stress reaches peak value, the softening is greater than hardening, and the deformation comes in the stable flow state. The peak stress decreases with the increase of temperature (the opposite situation for strain rate). The hot deformation activation energy of LZ31 alloy is Q = 149.85 kJ/mol. For the microstructure evolution, when the temperature is lower and the strain rate is higher, the softening mechanism of the alloy is dynamic recovery and dynamic recrystallization. Meanwhile, significant slip steps can be observed at the grain boundaries, which means the main deformation mechanism is dislocation slip. When the temperature gradually increases and the strain rate gradually decreases, the dynamic recovery disappears, and the main softening mechanism is continuous dynamic recrystallization.