A CDRX-based material model for hot deformation of aluminium alloys

Abstract

During hot deformation, continuous dynamic recrystallisation (CDRX) is believed to occur, and even dominates microstructural evolution in many metallic materials with high stacking fault energy, such as aluminium alloys. A unique material model for hot deformation of aluminium alloys is proposed in this paper, based on consideration of two processes: (i) increase of dislocation density, induced by plastic deformation, leading to generation, rotation and migration of low angle grain boundaries (LABs) and their transformation into high angle grain boundaries (HABs); (ii) migration of HABs leading to annihilation of both LABs and HABs. At large strain, the above counteracting processes, guided by different mechanisms, lead to saturation of HABs fraction. The model is applied to hot deformation of AA5052 and AA7050 alloys under various temperatures and strain rates, and calculated flow stress, HABs fraction and grain size evolution for both alloys agree well with the corresponding experimental data. The capability of predicting saturation of HABs fraction and average subgrain misorientation angle of both alloys under large strains demonstrate the potential applicability of the model to a wide range of hot forming process conditions.

A Review of Microstructural Evolution and Modelling of Aluminium Alloys under Hot Forming Conditions

“…For GDRX, however, there is still no relevant physically based model that characterises its mechanism in particular. Figure 20 is as an example showing the predictions of the viscoplastic behaviour and the associated microstructures of AA7075 during compression with various strain rates and temperatures, using a physically-based model [143]. Overall, reasonable predictions were achieved under the temperature and strain rate ranges studied, especially for the flow stress curves.…”

“…For CDRX, however, different mechanisms and microstructural evolution take place during hot deformation. This model has been modified to characterise CDRX for the hot deformation of Al alloys using different representative variables such as subgrain rotation and GB areas [142,143]. The CDRX-based models consider the evolution of dislocations, LAGB and HAGB, and are based on physical phenomena including accumulation, migration, rotation and annihilation of these microstructural constituents.…”

Simulation of Continuous Dynamic Recrystallization Using a Level-Set Method

“…This work still inspires many researchers and some recent articles illustrate attempts at expanding it. These publications especially highlight that additional phenomena can be considered, such as post-dynamic recrystallization (PDRX) [ 15 ], precipitate–dislocation interactions [ 16 ], and saturation of the average subgrain disorientation [ 17 ]. These studies [ 15 , 16 , 17 ] confirmed the ability of the Gourdet–Montheillet model to simulate CDRX.…”

“…These publications especially highlight that additional phenomena can be considered, such as post-dynamic recrystallization (PDRX) [ 15 ], precipitate–dislocation interactions [ 16 ], and saturation of the average subgrain disorientation [ 17 ]. These studies [ 15 , 16 , 17 ] confirmed the ability of the Gourdet–Montheillet model to simulate CDRX. Nevertheless, the models used within these studies suffer from the intrinsic limitations of mean-field approximations, which makes consideration of microstructure heterogeneities impossible.…”

An efficient numerical integration system for stiff unified constitutive equations for metal forming applications

“…The proposed algorithms are found to be best in their class, combining computational efficiency and strong stability. In addition, these methods make more efficient use of current computer resources and are particularly well suited to viscoplastic flow/creep constitutive equations, where the solution is determined implicitly by choice of the material dependent variables [8][9][10][11]. Three implicit numerical integration methods are outlined for used for numerical integrating stiff mechanism-based constitutive equations.…”