Abstract.

A two-dimensional quantitative cellular automaton (CA) model is employed to simulate dendrite arm fragmentation and dendrite arm coarsening in mushy zones. The phenomenon of dendrite arm fragmentation of an Al-Cu alloy during heating is well represented by the CA simulation, and it is analyzed in detail by comparing the local actual concentration and local equilibrium concentration. The CA simulations for the dendritic microstructures of SCN-ACE alloys during isothermal holding in a mushy zone reproduce the typical dendrite coarsening features as observed in experiments. The effects of holding temperature and alloy composition on the microstructures and dendrite coarsening kinetics are investigated. It is found that the melting of small dendrite arms and interdendritic groove advancement are the two main mechanisms in dendrite coarsening. The mechanism of coalescence by joining arm tips is more likely to take place at a lower temperature or for a lower alloy composition, while the dendrite arm fragmentation mechanism tends to occur at a higher temperature. The coarsening rate constant is found to decrease with increasing holding temperature and alloy composition.

Graphical abstract

中文翻译：

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枝晶臂断裂和枝晶臂粗化的模型⋆。

摘要。

二维定量细胞自动机（CA）模型用于模拟糊状臂碎裂和糊状区中的树枝状臂粗化。CA模拟很好地表示了Al-Cu合金在加热过程中枝晶臂断裂的现象，并通过比较局部实际浓度和局部平衡浓度对其进行了详细分析。对SCN-ACE合金等温保持在糊状区中的树枝状显微组织的CA模拟重现了实验中观察到的典型枝晶粗化特征。研究了保温温度和合金成分对显微组织和枝晶粗化动力学的影响。研究发现，小枝晶臂的熔化和枝晶间沟槽的发展是枝晶粗化的两个主要机理。通过连接臂尖端的合并机制更可能在较低温度或较低合金成分下发生，而枝晶臂断裂机制则倾向于在较高温度下发生。发现粗化速率常数随着保持温度和合金组成的增加而降低。

图形概要