Microstructural Evolution in a Commercial Al-Mg-Sc Alloy during ECAP at 300℃

摘要

Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a commercial coarse-grained Al-6%Mg-0.4%Mn-0.3%Sc alloy at a temperature of 300℃ (～0.6T_m). Samples were pressed using route A to a total strain of 12 and quenched in water after each ECAP pass. ECAP at moderate-to-high strains leads to the formation of a bimodal grain structure with grain sizes of around 1 and 8 μm and volume fractions of 0.3 and 0.6, respectively. The development of new-grained regions has been shown to result from a concurrent operation of continuous dynamic recrystallization that occurs during deformation and static recrystallization that occurs during each ECAP cycle by the exposure of the as-deformed material in the die kept at 300℃ for around 1.5 minutes. The microstructural development during warm-to-hot ECAP is discussed in terms of the enhanced driving force for recrystallization, resulting from the evolution of high-density dislocation substructures due to the localization of plastic flow and inhibition of recovery in the present alloy.