AN INVESTIGATION OF DUCTILITY AND MICROSTRUCTURAL EVOLUTION IN AN AL-3-PERCENT MG ALLOY WITH SUBMICRON GRAIN-SIZE

A submicrometer-grained (SMG) Al-3% Mg solid solution alloy, with an initial grain size of approximately 0.2 mum, was produced by intense plastic straining. Experiments show that tensile specimens of the SMG alloy exhibit high elongations to failure at low testing strain rates at the relatively low temperature of 403 K. The stress exponent is high (approximately 7-8) and calculations show deformation is within the region of power-law breakdown. The initial microstructure of the alloy consists of diffuse boundaries between highly deformed grains. At strain rates of approximately 10(-4) s-1 and lower, plastic deformation leads to dynamic recrystallization and the formation of highly nonequilibrium grain boundaries that gradually evolve into a more equilibrated configuration.