A Model for Static Recrystallization through Strain-Induced Boundary Migration

Abstract

Control over the inelastic deformation of polycrystals aimed at achieving desired performance characteristics of finished products is impossible without analyzing the structural evolution of the material at different scale levels. A major task in this respect is to develop physically sound mathematical models for describing the internal structure evolution as it determines the material properties. An effective tool for addressing this task is a multilevel approach to describing the thermomechanical processing of crystalline materials, in which carriers and physical mechanisms of processes are considered explicitly. Thermomechanical processing allows a good control over the defect and grain/subgrain structure of the material to achieve desired macrocharacteristics. This paper explores the subgrain/grain structure evolution during static recrystallization that occurs through strain-induced boundary migration. Modeling is carried out in two stages. The first stage models the plastic deformation of a crystalline material at room temperature. The second stage considers holding at an elevated temperature resulting in recrystallization. Both stages are modeled within a unified multilevel approach. The problem of modeling static recrystallization is formulated, and an algorithm for its numerical implementation is described. The modeling results are obtained for a bicrystal in which each grain is represented by a group of lower-scale elements (subgrains). Recrystallization causes profound changes in the subgrain structure geometry, the average size of subgrains, and their shape change. Recrystallized subgrains are more elongated compared to the original ones. During recrystallization more defective grains are replaced with less defective grains, and as a result the energy stored in the material decreases. The developed model qualitatively describes the release of stored energy. Numerical experiments revealed a critical plastic strain value below which recrystallization does not occur.