Modeling of Abnormal Grain Growth That Considers Anisotropic Grain Boundary Energies by Cellular Automaton Model

A new cellular automaton (CA) model of abnormal grain growth (AGG) that considers anisotropic grain boundary energies was developed in this paper. The anisotropic grain boundary energy was expressed based on two types of grains, which correspond to two components of different crystallographic orientation in textured materials. The CA model was established by assigning different grain boundary energies and grain-growth-driven mechanisms to four types of grain boundaries formed by two types of grains. The grain boundaries formed by different kinds of grains adopted the lowest energy principle, while the grain boundaries formed by the same kind of grains adopted the curvature-driven mechanism. The morphology calculated by the CA model shows the characteristics of AGG. Then, the Johnson-Mehl-Avrami (JMA) model was fitted to predict the growth kinetics. By analyzing the fitting results, the JMA model is capable of predicting the growth kinetics of AGG. The Avrami exponent p decreases from about 1.5 to 1 with the initial number of Type II grains increasing. The investigation of the Hillert model and grain size distribution further indicates that the microstructure evolution is consistent with AGG. Therefore, the analysis of morphology and kinetics indicates that AGG can be fairly well-simulated by the present CA model.