Microstructure evolution during dynamic discontinuous recrystallization in particle-containing Cu

Control of the grain size in a material is vital in many engineering applications. Evolving through recrystallization, the grain size is strongly influenced by the presence of impurity particles. These particles exert drag forces on migrating grain boundaries and prevent grain boundary motion by pinning of the boundaries. Taking copper as example material, the present work establishes a novel simulation model where dynamic discontinuous recrystallization is influenced by particle drag. The recrystallization kinetics are established on a microlevel and the simulations are performed using a 3D cellular automaton algorithm with probabilistic cell state switches. By this approach, computational efficiency is combined with high temporal and spatial resolution of the microstructure evolution. The simulated microstructure changes are in good agreement with experimental findings and the recrystallization kinetics are shown to comply with classical Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory. In addition, through homogenization, the macroscopic flow stress behavior is studied and is also shown to exhibit the expected transition from single-peak stable flow into serrated multiple-peak flow as the processing temperature is increased. Influence of changed initial grain sizes is studied and, in compliance with experimental data, an increased initial grain size stabilizes the flow stress behavior whereas the opposite trend is found for reduced initial grain sizes. Introducing impurity particles in the simulations, the progression of recrystallization is retarded and optimum values of the particle dispersion level are identified at different temperatures, allowing minimization of the recrystallized grain size during thermomechanical processing of the material.