Construction of an Arrhenius constitutive model for Mg-Y-Nd-Zr-Gd rare earth magnesium alloy based on the Zener-Hollomon parameter and objective evaluation of its accuracy in the twinning-rich intervals

Abstract

According to a high-temperature compression test of rare earth magnesium alloy (WE43), a strain-compensated constitutive model of the Arrhenius equation based on Zener-Hollomon parameters was established, and the rheological behaviors were predicted. The model exhibited relatively serious prediction distortion in the low-temperature and high-strain rate parameter interval, and its accuracy was still unsatisfactory even after modification by a correction operator considering the coupling of temperature and strain rate. The microstructure characterization and statistical analysis showed that a large number of twinning occurred in the parameter intervals with prediction deviation. The occurrence of twinning complicated the local internal stress distribution by drastically changing the crystal orientation and led to significant fluctuations in the macroscopic strain-stress and hardening curves relative to the rheological processes dominated by the dislocation and softening mechanisms, making the logarithm of the strain rate and stress deviate from the linear relationship. This twinning phenomenon was greatly influenced by the temperature and strain rate. Herein, the influence mechanism on twinning behavior was analyzed from the perspective of the interaction of dislocation and twinning.

Keywords

• RE magnesium alloy
• Hot deformation
• Zener-Hollomon parameters
• Arrhenius constitutive model
• Dislocation
• Twinning