Hot deformation and processing map of an as-extruded Mg-Zn-Mn-Y alloy containing I and W phases

The hot deformation characteristics of an as-extruded ZM31 (Mg-Zn-Mn) magnesium alloy with an addition of 3.2 wt.% Y, namely ZM31 + 32Y, have been studied via isothermal compression testing in a temperature range of 300-400 degrees C and a strain rate range of 0.001-1 s(-1). A constitutive model based on hyperbolic-sine equation along with processing maps was used to describe the dependence of flow stress on the strain, strain rate, and deformation temperature. The flow stress was observed to decrease with increasing deformation temperature and decreasing strain rate. The deformation activation energy of this alloy was obtained to be 241 kl/mol. The processing maps at true strains of 0.1, 0.2, 0.3 and 0.4 were generated to determine the region of hot workability of the alloy, with the optimum hot working parameters being identified as deformation temperatures of 340-500 degrees C and strain rates of 0.001-0.03 s(-1). EBSD examinations revealed that the dynamic recrystallization occurred more extensively and the volume fraction of dynamic recrystallization increased with increasing deformation temperature. The role of element Y and second-phase particles (I- and W-phases) during hot compressive deformation was discussed. (C) 2015 Elsevier Ltd. All rights reserved.