Hot deformation behavior of Mg-5Li-3Al-2Zn-0.2Zr alloy based on constitutive analysis, processing map, and microstructure evolution

Abstract

The hot deformation behavior of Mg-5Li-3Al-2Zn-0.2Zr alloy was investigated via hot compression tests at 573–673 K/0.001–1 s−1. True stress-strain curves exhibit typical dynamic recrystallization characteristic, the proposed strain-compensated Zener-Hollomon model shows high accuracy in predicting flow stress, and the average activation energy of the alloy is calculated as 164.2196 kJ·mol−1. The instability region spans all temperatures at higher strain rates and the cause is the formation of local deformation bands composed of ultrafine recrystallized grains. The optimum deformation processing for Mg-5Li-3Al-2Zn-0.2Zr alloy is determined as 673 K/0.001 s−1. The microstructure evolution reveals that the alloy compressed at 573–623 K mainly undergoes continuous dynamic recrystallization controlled by dislocation cross-slip, and the alloy compressed at 673 K mainly undergoes discontinuous dynamic recrystallization controlled by dislocation climb.