Hot deformation behavior of Mg-8Li-3Al-2Zn-0.2Zr alloy based on constitutive analysis, dynamic recrystallization kinetics, and processing map

Abstract

The hot deformation behavior of as-homogenized Mg-8Li-3Al-2Zn-0.2Zr alloy was investigated by compression test at 473–623 K/0.001–1 s−1. The relationship of flow stress, temperature, strain rate, and strain is represented by the Zener-Hollomon parameter including Arrhenius term, and the average activation energy of deformation is calculated as 107.55 kJ·mol−1. The dynamic recrystallization (DRX) kinetics model of Mg-8Li-3Al-2Zn-0.2Zr alloy is established as XDRX=1−exp[−0.2413(ε−εcε*)1.7875]. The microstructure evolution indicates that DRX process is retarded in α-Mg phase because of the preferred DRX of β-Li phase and the spheroidization of α-Mg phase leading to a decrease in DRX driving force of α-Mg phase. The processing map at strain of 0.7 exhibits a region of discontinuous DRX occurring at 573–623 K with strain rate of 0.001–0.01 s−1 and 523 K with stain rate of 0.001 s−1, which are the optimum parameters of hot working for optimizing the workability and microstructure of Mg-8Li-3Al-2Zn-0.2Zr alloy.