Microstructural and constitutive analysis in process modeling of hot working: the case of a Mg-Zn-Mn alloy

This study presents an analysis of the microstructural evolution and flow stress variation with strain of a Mg-2%Zn-1%Mn alloy during hot deformation, carried out through a combination of torsion experiments, electron backscatter diffraction (EBSD) studies and constitutive analysis. Straining was observed to produce dynamic recrystallization (DRX). It emerged that such DRX was sluggish at 250 °C, while almost complete grain refinement occurred at 350 °C. A further increase in temperature led to concurrent grain growth and dynamic recrystallization, resulting in coarse grain size. A modified strain-dependent form of the Garofalo equation was used in the constitutive analysis, obtaining a more than satisfactory description of the experimental results. The extrapolation of the model in the low strain rate/high strain regions led to an equally satisfactory description of the experimental data. The analysis of the variation of the activation energy for hot working, which was equivalent to the activation energy for self-diffusion, suggested that deformation was recovery-controlled in most of the range of the experimental conditions investigated.