Experimental study of grain structures evolution and constitutive model of isothermal deformed 2A14 aluminum alloy

Softening mechanism and microstructure evolution of 2A14 aluminum alloy were studied via isothermal deformation tests under the temperatures range from 573 K to 773 K and strain rates range from 10−3 s−1 to 1 s−1. Microstructures indicated that the grain structure was composed of massive fine sub-grains while only a small quantity of recrystallized grains formed along grain boundaries. The quantity of sub-grains increased with the decrease of deformation temperature or the increase of deformation strain rate, and the correlations between the deformation conditions and the geometrically necessary dislocation (GND) and stored strain energy were illuminated with quantification. The softening mechanism under different conditions was in compliance with the analysis of processing map. The microstructure indicated that the governing dynamic softening mechanism was the dynamic recovery for the temperature below 773 K, and dynamic recrystallization played the dominant role in the softening mechanism at low strain rates for the temperature at 773 K. The Arrhenius constitutive model and physical-based constitutive model considering lattice diffusion have been established, and both two models can well predict the flow stress and GND density of 2A14 aluminum alloy.