基于一种改进CA模型的微观组织模拟

NUMERICAL SIMULATION OF MICROSTRUCTURE EVOLUTION BASED ON A MODIFIED CA METHOD

基于热传输、溶质传输等基本传输过程及晶粒生长物理过程,建立了单相合金凝固过程微观组织及枝晶形貌演化的三维数学模型,并提出了新的生长模型和单元捕获规则,新规则在三维立方有限差分单元的基础上保证了晶粒在各个随机的优先生长方向生长时的枝晶连续性,并较好的在三维立方网格中体现出了晶粒形貌．此外,模型中考虑了成分过冷、曲率过冷和晶粒随机各向异性生长等重要因素．数值模拟结果表明．所建立的数学模型能够合理描述晶粒沿任意角度生长的过程,温度场、溶质场和微观组织形貌的模拟计算结果合理．多晶核定向生长模拟结果表明,多晶核定向竞争生长达到稳定状态时,枝晶间的一次枝晶臂间距与初始形核数目无关．所建立的模型和晶粒捕获规则适用于进一步定向凝固微观组织演化的研究．

Based on the basic transfer process, including heat transfer and solute transfer, and the physics of growth process of crystal grains, the mathematical models for the 3D simulation of microstructure and free dendritic growth of single phase alloy were developed and a new capturing rule was presented. Many factors such as constitutional undercooling, curvature undercooling and grain growth in random preferential growth directions, which had vital influences on the evolution of microstructure, were considered in the model. Simulated results showed that the grain growth in random preferential growth directions can be described by the model reasonably, and the simulated results were coincident with actual phenomena. The simulation results of directional growth of multiple nuclei indicated that the primary dendrite space was independent of initial nuclei number when the growth reached a stable state. The model and the capturing rule are suitable to further research of microstructure evolution of directional solidification.