Simulation of Continuous Dynamic Recrystallization Using a Level-Set Method

Abstract

Dynamic recrystallization is one of the main phenomena responsible for microstructure evolution during hot forming. Consequently, obtaining a better understanding of dynamic recrystallization mechanisms and being able to predict them is crucial. This paper proposes a full-field numerical framework to predict the evolution of subgrain structures upon grain growth, continuous dynamic recrystallization, and post-dynamic recrystallization. To be able to consider a subgrain structure, two strategies are proposed. One relies on a two-step tessellation algorithm to generate a fully substructured microstructure. The second strategy enables for the simulation of the formation of new subgrains during hot deformation. Using these tools, the grain growth of a fully substructured microstructure is modeled. The influence of microstructure topology, subgrain parameters, and some remaining stored energy due to plastic deformation is discussed. The results highlight that the selective growth of a limited number of subgrains is observed only when mobility is a sigmoidal function of disorientation. The recrystallization kinetics predicted with different criteria for discrimination of recrystallized grains are quantitatively compared. Finally, the ability of the framework to model continuous dynamic and post-dynamic recrystallization is assessed upon a case study representative of the hot extrusion of a zircaloy-4 billet (T=650 °C;ε˙=1.0s−1;εf=1.35). The influence of grain boundary properties and nucleation rules are quantified to evaluate the model sensitivity and suitability. Application of these numerical tools to other thermomechanical conditions and microstructures will be presented in an upcoming article.

Statistics of grain microstructure evolution under anisotropic grain boundary energies and mobilities using threshold-dynamics

“…The initial microstructure for case 2b is shown in figure 9(a), wherein the TBs are the boundaries between type A (red) and type E (blue) grains. It was generated using a two-level Voronoi tessellation [70]. The coarselevel Voronoi seeds are used to determine group types, while the 30 ×-refined seeds define specific orientation values.…”

Modeling CDRX and MDRX during hot forming of zircaloy-4

“…Some additional details about this method are provided in several articles [7,19] and an extension is proposed in the following Stored energy gradients paragraph. The implementations dedicated to CDRX are described extensively in [20].…”

“…Description of the thermomechanical conditions of the hot compression campaigns[8]. (a) Hot compression with equiaxed microstructures (Eq).…”

A Multilevel Physically Based Model of Recrystallization: Analysis of the Influence of Subgrain Coalescence at Grain Boundaries on the Formation of Recrystallization Nuclei in Metals

“…Therefore, the formulated problem is solved in the framework of the advanced statistical model of inelastic deformation, which permits the consideration of the interactions between adjacent structural elements (subgrains, grains) [ 27 , 34 ]. The modeling of coalescence for a representative volume of subgrains with consideration of their geometry as similar to real three-dimensional geometry is a laborious and complex task [ 35 , 36 , 37 ]. Most models of recrystallization that deal with subgrain coalescence are simplified models.…”