Microstructure behavior of Al-Mg-Sc alloy processed by ECAP at elevated temperature

Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a coarse-grained Al-6% Mg-0.4% Mn-0.3% Sc alloy at 300 °C (∼0.6T_m). Samples were pressed to strain 12 and quenched in water after each pass. ECAP at moderate-to-high strains leads to formation of a bimodal grain structure, with grain sizes of about 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 the concurrent operation of the continuous dynamic recrystallization that occurs during deformation and the static recrystallization that occurs by the exposure of the as-deformed material in the die kept at 300 °C and/or reheating between pressings. The microstructural development is discussed in terms of the enhanced driving force for recrystallization, resulting from the evolution of high-density dislocation substructures due to localization of plastic flow and inhibition of recovery in the present alloy.