Constitutive behavior, microstructural evolution and processing map of extruded Al–1.1Mn–0.3Mg–0.25RE alloy during hot compression

Abstract

Hot compression tests of an extruded Al–1.1Mn–0.3Mg–0.25RE alloy were performed on Gleeble–1500 system in the temperature range of 300–500 °C and strain rate range of 0.01–10 s−1. The associated microstructural evolutions were studied by observation of optical and transmission electron microscopes. The results show that the peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener–Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 186.48 kJ/mol. The steady flow behavior results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of constituent particles. The main constituent particles are enriched rare earth phases. Positive purifying effects on impurity elements of Fe and Si are shown in the Al–1.1Mn–0.3Mg–0.25RE alloy, which increases the workability at high temperature. Processing map was calculated and an optimum processing was determined with deformation temperature of 440–450 °C and strain rate of 0.01 s−1.