A new cellular automata model for hot deformation behavior of AZ80A magnesium alloy considering topological technique

Abstract

In this paper, the CA model of grain topological deformation technique (T-CA) and the physical constitutive model considering strain are introduced to study the hot deformation behavior of extruded AZ80A magnesium alloy. The isothermal compression test of extruded AZ80A magnesium alloy was carried out on the Gleeble-3800 thermal simulator. The deformation temperature and strain rate were 598 K∼723 K and 0.001 s−1∼1 s−1, respectively. According to the experimental results, a phenomenological constitutive model of flow stress considering strain was constructed. The reliability of the model was verified by comparing the experimental and predicted flow stress. The influence of thermal deformation parameters, i.e., deformation temperature, strain rate, and strain, on the DRX kinetic curve and grain size evolution was studied based on the CA model with the introduction of grain topological (T-CA) deformation technology. Meanwhile, the influence of initial grain size on dynamic recrystallization was studied using the conventional CA model (C-CA) and the CA model with topological deformation (T-CA) technology. Finally, the accuracy of the T-CA model was verified by combining physical experiments and electron backscatter diffraction (EBSD) technology. At the temperature of 598 K, the strain rate of 0.1 s−1, and the strain of 0.91, the error between the average grain size simulated by the topological CA (T-CA) model and the experimental results is 7.6 %, which is consistent with the experimental results. When the initial grain size is 43 µm, compared with the conventional CA simulation method (C-CA), the CA simulation method with the introduction of grain topological deformation can promote the occurrence of recrystallization, improving the simulation speed and accuracy. The error between the percentage of recrystallization and the experiment is 4.5 % and 3.2 %, respectively, indicating that the simulation method with the introduction of grain topological deformation (T-CA) can accurately predict the dynamic recrystallization behavior of AZ80A magnesium alloy.