Hot Workability of Dual-Phase Mg-Li Alloy with α→β Trans-formation at Elevated Temperatures

Abstract:

Hot workability, microstructure evolution, and phase composition of dual-phase Mg-Li alloy were investigated via hot compression test at 250?400 °C with strain rates of 0.1?10 s^-1. The optimum hot workability window integrating processing and α-Mg content maps was established. Results show that the established Arrhenius constitutive model can accurately predict the stress flow behavior during work softening. In addition, the microstructure of the alloy shows that dynamic recovery (DRV), dynamic recrystallization (DRX) and α-Mg phase transformation are the main softening mechanisms. α-Mg phase is transformed into β-Li phase in forms of both spheroidization and internal precipitation of α-Mg phase, especially above 300 °C. Meanwhile, the DRX process can easily occur in β-Li phase, whereas in the α-Mg phase it is retarded. Based on the dynamic materials model and microstructure analysis, the optimal processing window can be obtained as 300?350 °C/0.1?1 s^-1 and 250 °C/0.1 s^-1.