Cellular Automata Simulation Of Microstructure Evolution Of Grain Growth

It is an important research issues in grain growth of polycrystalline materials. The microstructures of materials affect theirs macroscopic behavior directly. It is of significance to understand the rule of microstructure evolutionto control the microstructures of materials in practical applications. The microstructures evolution of grain’growth was simulated by Cellular Automata (CA) method in this article. The grain growth kinetics, morphology, topology relations and dynamic recrystallization were studied based on simulation results. The simulation results show that the CA model can more accurately reflect the normal grain growth law, grain topological arrangement, a variety of important features of the grain growth and the microstructure evolution of dynamic recrystallization. It can provide the basis for controlling the evolution of the grain microstructure.First of all, a two dimension normal grain growth CA model was build up according to the physical mechanism of grain growth. It is based on Metropolis algorithm by introducing thermodynamic energy fluctuation of probabilistic mechanism. The CA program was written by Fortran language. The process of grain growth was simulated under isothermal annealing conditions. The snapshots of the evolution of grain microstructure at different times were obtained though visualization of numerical results and the evolution of microstructure can be observed directly. Then, the grain size, number of grain and grain edges statistical algorithm were written and the statistic data of simulation results were analyzed. The simulation results show that the grain growth exponent in the early stage of grain growth is slightly higher than that of stable state. The kinetics of the grain growth exponent n=0.41345in stable state, the grain size distribution follows log-normal distribution well and the grain size and edge distributions exhibit good self-similarity nature. The relationship between the grain edges and the average number of the edges of all its neighbors was analyzed and it is validated that theirs relationship meets the Aboav-Weaire law. The Aboav-Weaire law’s a parameter is1.03291and μ2, parameter is1.8240. By contrast, a phase field model of grain growth was established to illustrate the efficiency of CA model. The efficiency of the two models was quantitatively studied and the results show that the CA model is highly time efficient and suitable for large-scale numerical simulation.Besides, the two-dimensional CA model was extended to three-dimensional space to study the three-dimensional grain growth phenomenon. The evolutions of three-dimensional microstructures were obtained. The grain growth law was studied using cross section method by interception different cross sections form three dimension. The three dimensions grain growth that simulated by CA model is more stable than that of two dimensions by studying from the kinetic analysis curve. The grain size distribution follows log-normal distribution well and the grain size and edge distributions show good self-similarity nature.At last, a dynamic recrystallization microstructure evolution of CA model was established according to the mechanism of the evolution of the dislocation density, the nucleation of new grains and the grain growth kinetics during thermal deformation process. Using the material parameters obtained on Gleeble-3500thermo-mechanical simulator by isothermal compression, the microstructure evolution of dynamic recrystallization was simulated by CA model. The snapshots of the microstructure evolution of dynamic recrystallization and flow curves were obtained. The simulated results show well corresponding to the experimental result.The CA method can fully reflect normal grain growth phenomena, effectively predict the microstructure and mechanical properties of the materials quantitatively and it can be able to provide reference for controlling grain growth.