Optimum parameters and kinetic analysis for hot working of a solution-treated Mg-Zn-Y-Mn magnesium alloy

Abstract

The flow behavior, dynamic recrystallization (DRX) evolution and hot workability of the solution-treated Mg94Zn2.5Y2.5Mn1 (at%) alloy were investigated by hot compression tests. Compression tests were performed in the temperature range of 350–500 °C and the strain rate range of 0.001–1 s−1 on a Gleeble-1500D thermo-mechanical simulator. Using regression analysis for the constitutive equation of the flow behavior, the average activation energy of deformation and the stress exponent were determined to be 302.22 kJ/mol and 8.60452, respectively. The flow stress of the Mg94Zn2.5Y2.5Mn1 alloy predicted by the proposed models well agrees with experimental results. The kinetic model of DRX was proposed based on the analysis of true stress-strain data, which can be described as XDRX=1−exp[−2.15((ε−εc)/ε∗)1.51]. The DRX kinetic model was validated by means of microstructure observation. Furthermore, processing maps were developed and analyzed based on the dynamic material model (DMM). The flow instability regions and stability regions were identified based on the processing maps; the optimum domain for hot working of the experimental alloy are temperatures ranging from 400 °C to 450 °C and strain rates ranging from 0.001 s−1 to 0.01 s−1. Finally, a hot extrusion test was performed according to the optimum deformation parameters. The deformed sample exhibited a good surface quality and excellent mechanical properties, which verified the reasonability of the optimal deformation parameters.