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

Abstract

a b s t r a c tA 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.

Dynamic Recrystallization and Hot Workability of 316LN Stainless Steel

“…Cram [6] extended and successfully applied a physically based description for nucleation in static recrystallization to nucleation during dynamic recrystallization (DRX), and comparisons between experiment and model calculations showed good agreement over a wide range of deformation temperature, initial grain size, and applied strain rate. Beltran [7] developed and validated a model describing recrystallization in metallic materials capable of handling DRX, post-dynamic recrystallization (PDRX), and grain growth against experimental test cases for multi-pass hot deformation of 304L austenitic stainless steel, predicting microstructural evolution due to different recrystallization regimes through a modified Kocks-Mecking equation. Madej [8] compared the mean and full field dynamic recrystallization models and concluded that full field approaches additionally extend predictive capabilities of DRX models by incorporating microstructure evolution in an explicit manner.…”

A new topological approach for the mean field modeling of dynamic recrystallization

“…Furthermore the predicted grain size distributions are improved as compared to former mean field models [14,15,16,17] even if their are still quite far from experimental ones.…”

“…This limitation is due to the fact that all grains which have nucleated at a given time have the same evolution (in size and dislocation density) in mean field models [14,15,16,17] whereas in a real microstructure, each grain evolves depending on 60 its own neighborhood. Therefore, in this work a new topological approach for the mean field modeling of DRX is proposed.…”

“…In addition, the evolution of principal lengths of the grains (in the sense of idealized ellipsoid shapes) are modeled during deformation in the NHM, as explained in section 4. Finally, the results of simulations related to hot forging of a 304L austenitic steel provided by the NHM, 70 the mean field model of Beltran [17] and a full field level-set model [19] are presented in section 5.…”

“…Hereafter, this new model will be called "NeighborHood Model (NHM)". The NHM is based on the same constitutive equations used in the mean field model of Beltran et al [17] for modeling strain hardening, recovery and nucleation. These laws are introduced in section 2.…”