Transition of Viscoplasticity from the Single Crystal to the Polycrystal Level

Abstract

Based on the activation processes involved, a temperature-dependent micromechanical theory is developed to determine the viscoplastic behavior of a polycrystal from those of its constituent grains. This model assumes dislocation-glide to provide the only significant contribution to the overall plastic strain and it leads to the formulation of microconstitutive equations that describe the primary and steady-state creep of slip systems. These equations are used to describe the viscoplastic behavior of the slip systems and by which, that of the constituent grains. Together with the self-consistent relation, the viscoplastic stress-strain relations of a polycrystal under a constant total strain-rate are determined by an averaging process over the behavior of its constituent grains. The theory is applied to model the behavior of RR59 aluminum alloy at some selected strain rates and temperatures.