Deformation behavior and microstructure evolution induced by nano-sized Al6Mn phase particles in a homogenized Al–6Mg–0.8Mn alloy during hot compression

Abstract

In the present work, hot compression deformation behavior and microstructure evolution in a homogenized Al–6Mg–0.8Mn alloy with nano-sized Al6Mn phase particles were investigated at the temperature ranging from 300 to 500 °C with tha strain rate of 0.001–1 s−1. The constitutive equation of the Al–6Mg–0.8Mn alloy was established and the average deformation activation energy was calculated to be 167.07 kJ/mol. The flow stress of the alloy decreased with increasing the compression temperature and raised with increasing the strain rate, which was closely associated with the competitive relationship between work hardening and dynamic recovery (DRV). The low compression temperature accelerated the formation of shear bands in the alloy. The low strain rate was beneficial for the generation of low-angle grain boundaries (LAGBs), and the high compression temperature and strain rate promoted dynamic recrystallization (DRX). The interaction between the nano-sized Al6Mn phase particles participating near the initial grain boundaries and mobile dislocations facilitated the generation of LAGBs. Discontinuous DRX through grain boundary bulging mechanisms and continuous DRX with the LAGBs transforming to HAGBs led to the preferred formation of recrystallized grains along the initial large-sized grains. Furthermore, this interaction also resulted in the dissolution of Al6Mn phase particles.