| With the increasingly prominent problem of energy crisis,magnesium alloy has been widely used in structural lightweight owing to their advantages of low density,high specific stiffness,specific strength,good shock absorption,etc.,which is crucial to the lightweight of automobile manufacturing,military industry and 3C products.Due to the dense hexagonal structure of magnesium alloy,its plastic deformation ability at room temperature is severely affected,which hinders its widespread application in the industrial field.Thermoplastic deformation has become a commonly used method for plastic forming of magnesium alloys,which can lead to the evolution of the microstructure of magnesium alloys and improve their overall performance after plastic forming.Therefore,studying the plastic deformation behavior of magnesium alloys at high temperatures is more meaningful for improving their performance.At present,in the process of studying materials,computer technology provides another research method for simulating dynamic recrystallization（DRX）behavior.Cellular automata method can truly reflect the migration process of grain boundaries and can be used to predict the microstructure evolution of different materials in dynamic recrystallization（DRX）behavior.Isothermal compression tests were conducted on the Gleeble-3800 thermal simulator to obtain rheological stress-strain curves at different temperatures（598K,623K,648K,673K,698K,723K）and strain rates(0001s-1,0.01s-1,0.1s-1,1s-1).Constitutive models,dynamic recrystallization models,and grain size models were established,and the required simulation parameters for cellular automata were obtained.A cellular automata model for normal grain growth of extruded AZ80A magnesium alloy was established using thermal activation energy,migration rules of cells,curvature driving principle,and grain boundary energy dissipation mechanism as the conversion rules of cellular automata.The grains of extruded AZ80A magnesium alloy were simulated at a temperature of 400℃,and the results were compared with the experimental microstructure.The error in grain size between the two was 0.6%,This indicates that the model can accurately predict the generation of initial grains in extruded AZ80A magnesium alloy.Based on the theory of recrystallization nucleation and growth based on dislocation density,a cellular automata model for dynamic recrystallization of extruded AZ80A magnesium alloy during hot deformation was established.The dynamic changes of grains at different temperatures,strains,and strain rates were studied,as well as the effects of different parameters on recrystallization behavior.At the same time,the CA simulation results were compared and verified with experimental results,with an error of no more than 8%.In order to better achieve the topological deformation and microstructure evolution of grains during hot deformation of extruded AZ80A magnesium alloy,and to achieve the topological evolution of grain structure,a dynamic recrystallization model incorporating grain topological deformation technology is proposed.The effects of thermal deformation parameters（deformation temperature,strain rate,and strain）and initial grain size on DRX and grain size were studied by tracking the dislocation density of the cell.The results show that the maximum error between the CA simulation results and the experiment is4.4%,and the minimum error is 0.3%.Finally,in order to verify the reliability of the application of the extruded AZ80A magnesium alloy cellular automata model established in this article,the cellular automata method was combined with finite element method,and the thermophysical parameters obtained from DEFORM-3D simulation were introduced into the cellular automata model to simulate the microstructure evolution during actual thermal compression process.The simulation results of microstructure evolution and recrystallization volume fraction during dynamic recrystallization process tend to be consistent with experimental results,with good consistency. |
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