A mean field model of dynamic and post-dynamic recrystallization predicting kinetics, grain size and flow stress

A physically-based two-site mean field model has been developed to describe the microstructural evolution due to recrystallization during and after deformation. The model has been applied to predict the recrystallized fraction, recrystallized grain size, and flow stress of 304L austenitic stainless steel during discontinuous dynamic recrystallization (DDRX), post-dynamic recrystallization (PDRX) and grain growth (GG). The model parameters vary with temperature and strain rate but do not depend on grain size. In PDRX and GG regime, the parameters only depend on temperature. The model responds well to conditions with different temperatures, strain rates, strains and/or annealing times. Particular attention is paid to the occurrence of two-stage growth in the recrystallized grain size plots when PDRX occurs. There is a good quantitative agreement between model predictions and experimental results obtained in the different recrystallization regimes, opening the possibility of modeling multi-pass operations compatible with industrial applications. Recrystallization is an important phenomenon that causes microstructural changes in deformed materials, thereby affecting its properties. Many metallic components are produced from large castings, which are then further deformed by forging, extrusion, rolling, etc., into an intermediate or final product. Three different recrystallization behaviors are usually observed during these processes , namely, dynamic, post-dynamic and static recrystallization. The recrystallization regime depends on whether it occurs during hot deformation or between deformation intervals. In static recrystallization (SRX), the deformation is interrupted before reaching the critical strain for dynamic recrystallization (DRX), e DRX cr. During this recrystallization regime, both nucleation and growth of new grains take place during annealing periods between intervals of hot deformation. On the other hand, these processes can also be observed during deformation once e DRX cr is reached, leading to dynamic recrystallization. Post-dynamic recrystallization (PDRX) refers to the growth of dynamically formed nuclei once deformation (greater than e DRX cr) has come to an end. Grain growth (GG) is defined as the uniform coarsening of a material with a minimal dislocation content at a high temperature [1]. Although extensive efforts have been put on a wide range of materials, recrystallization during and following deformation is still not fully understood [2]. Experimentally, the softening fraction [3] during annealing of dynamically recrystallized microstructures was often used to differentiate recrystallization regimes, due to the fact that it is difficult to distinguish SRX and PDRX [4]. Researchers at McGill University were probably the first ones who investigated the post-dynamic softening. They proposed a mechanism involving three different …