Superplasticity is a promising technology aimed at manufacturing products of complex shapes with improved physical, mechanical and performance characteristics due to the fine-grained structure of materials. Deformation under superplastic conditions is characterized by lower loads on processing tools in comparison with conventional plastic working and by a reduction in the number of finishing operations. For many alloys prepared by methods of severe plastic deformation, experimental data on uniaxial tension in the range of relatively moderate temperatures and high strain rates, entering the superplasticity mode, staged (bell-shaped) stress-strain curves. This is associated with the action and interaction of various physical mechanisms and the change in their roles during deformation, as well as with the evolution of the defect structure in the material. These factors are influenced by temperature-strain rate conditions and by the structural characteristics of the material after preliminary processing, in particular, the shape and size of grains, the fraction of high-angle boundaries, the degree of recrystallization, and the presence of alloying additions that can form various phases in the material. The paper considers a modified statistical three-level constitutive model based on the crystal plasticity for describing superplastic deformation of an aluminum-magnesium alloy with an explicit consideration of crystallite boundaries and a change of their relative positions. The model takes into account the main deformation mechanisms: grain boundary sliding, intragranular dislocation sliding, and their interaction, as well as the processes of grain boundary diffusion, lattice rotations, and dynamic recrystallization. The paper introduces the model with a focus on a more detailed description of the influence of intermetallic particles on the material behavior. The results of numerical experiments for the aluminum-magnesium alloy 1565ch (Russian analogue of foreign alloy 5182), taking into account the particles of secondary phases, demonstrate satisfactory agreement with the experimental data.
Sharifullina et al. (Wed,) studied this question.