基于元胞自动机的三维晶粒生长动力学研究

Growth kinetics of three-dimensional grains based on cellular automata

摘要:

本文基于热力学转换机制和能量跃迁原理，采用Metropolis算法改进的元胞自动机模型，对AZ31镁合金三维晶粒长大过程进行仿真研究，并对其晶粒尺寸与晶粒长大动力学进行统计分析。仿真结果表明:采用改进转变规则后的元胞自动机模型更加接近于实际三维晶粒的正常长大过程。在模拟过程中，系统总自由能降低，不同时刻晶粒尺寸均呈现正态分布。晶粒直径与平均晶粒直径的比值R/Rm≈1.0的晶粒分布最多，满足晶粒演变最小能量准则。分析晶粒长大动力学可知，三维晶粒长大遵循晶粒演变过程中平均晶粒尺寸随时间变化的关系，晶粒长大指数为0.47941，非常接近于理论值0.5。通过实验对AZ31镁合金保温过程中晶粒尺寸变化规律进行研究，进一步验证了本文建立的三维元胞自动机模型的可靠性与准确性。

Abstract:

Based on the thermodynamic conversion mechanism and energy transition principle, the three-dimensional (3D) grain growth process of AZ31 magnesium alloy was simulated by using the improved cellular automata (CA) model of Metropolis algorithm, and the grain size and grain growth kinetics were analyzed statistically. The simulation results showed that CA model with the improved transformation rules was closer to the normal growth process of the actual 3D grain. In the simulation process, the total free energy of the system decreased, and the grain size presented normal distribution at different times. The ratio of grain diameter to average grain diameter (R/Rm) of 1.0 was the largest in grain distribution, which satisfied the minimum energy criterion of grain evolution. The analysis of grain growth kinetics showed that the 3D grain growth process follows the relationship between average grain size and time during grain evolution, and the grain growth index was 0.47941, which was much closed to the theoretical value of 0.5. The grain size variation of AZ31 magnesium alloy during heat preservation was studied by experiments, which further verified the reliability and accuracy of the 3D cellular automata model established in this paper.