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改进了前期工作建立的多相元胞自动机(multi-phase cellular automaton,MCA)模型,模拟以离异共晶方式凝固的球墨铸铁的显微组织演化.在模型中采用局部溶质平衡法计算石墨和奥氏体的生长动力学,并在石墨的生长模型中考虑石墨与Fe的密度比.该模型可以模拟出与实验观测相符合的显微组织形貌.应用该模型模拟分析了石墨与奥氏体的相互作用和竞争生长机制,讨论了冷却速率对凝固结束时石墨球大小和尺寸分布的影响,将模拟结果与实验结果进行了比较.结果表明:奥氏体的析出促进邻近石墨在液相中的生长;奥氏体和石墨两相的生长受C扩散控制;当石墨被奥氏体包围后,生长速度减慢.此外,随着冷却速率的增大,凝固时间缩短,石墨球平均半径减小,不同冷速条件下石墨球尺寸分布的变化规律与实验结果吻合较好.
The multi-phase cellular automaton (MCA) model established in the previous work was improved to simulate the microstructure evolution of dissimilar eutectic nodular cast iron.The local solute equilibrium method was used to calculate the graphite and Austenite growth kinetics, and graphite in the growth model to consider the density ratio of graphite and Fe. The model can simulate the experimental observations consistent with the morphology of the microstructure. The application of the model to simulate the relationship between graphite and austenite Body interaction and competition growth mechanism, the influence of cooling rate on the size and size distribution of graphite balls at the end of solidification was discussed, and the simulation results were compared with the experimental results.The results show that the precipitation of austenite promotes the formation of graphite in the liquid phase The growth of both austenite and graphite is controlled by diffusion of C; when graphite is surrounded by austenite, the growth rate slows down.In addition, as the cooling rate increases, the solidification time is shortened, the mean radius of graphite balls Decrease, and the variation of the size distribution of the graphite balls under different cooling rates are in good agreement with the experimental results.