Full field and mean field modeling of dynamic and post-dynamic recrystallization in 3D – Application to 304L steel

Final properties of metal alloys are directly related to their microstructure, inherited from the processing route. Dynamic (DRX) and post-dynamic recrystallization (PDRX) mechanisms play a primordial role in microstructure evolutions occurring during and after hot-deformation. Within this context, predicting microstructures depending on the applied thermomechanical conditions is a major challenge for both industrials and researchers. This requires a good knowledge of recrystallization mechanisms and kinetics. Full field models are based on an explicit description of the microstructure of a metallic alloy, and its possible evolutions at a polycrystalline scale. These models are accurate compared to models operating at larger scales, but they generally lead to prohibitive numerical costs. On the other hand, mean field models are based on an implicit description of the microstructure, leading to considerably reduced numerical costs, but they are based on many assumptions, notably with regards to topology. The outcome of this PhD work is a new full field model of DRX/PDRX and grain growth, working in 3D as well as in 2D, and a new DRX/PDRX mean field approach which better accounts for topological effects, and provides better predictions for grain size distributions. This work also includes a calibration procedure and a validation of these two new models, using experimental data obtained from compression tests performed on the 304L austenitic steel.