Abstract.

The microstructural evolution of a SCN-ACE alloy in a temperature gradient is studied by cellular automaton (CA) modeling and in situ experiments. The initially columnar dendrites gradually evolve to a completely solid region with a planar solid/liquid interface. The CA simulations and in situ observations present the migration of secondary dendrite arms and liquid pockets due to temperature gradient zone melting (TGZM), and the movement of the interface between a mushy zone and a fully liquid zone. The CA simulations show that the interface movement toward the lower temperature region is caused by the increasing concentration of the fully liquid region. Through updating the concentration in the fully liquid zone to the initial concentration in the CA simulation for mimicking the efficient stirring in liquid, the movement of the interface between the mushy zone and the fully liquid zone is hindered. The simulated liquid fractions and mean concentrations throughout the mushy zone decrease with time, which agree well with the analytical predictions. The simulated concentrations in the resolidified mushy zone are not higher than the temperature-dependent solidus concentrations, implying that no supersaturation remains after the mushy zone fully solidifies.

Graphical abstract

中文翻译：

---

在温度梯度下圆柱状树枝状微结构的同时熔化和凝固：数值模拟和实验⋆。

摘要。

通过细胞自动机（CA）建模和原位实验研究了SCN-ACE合金在温度梯度下的组织演变。最初的柱状树突逐渐演化为具有平面固/液界面的完全固体区域。CA模拟和原位观测结果表明，由于温度梯度带熔化（TGZM），次级枝晶臂和液体囊的迁移，以及糊状区和完全液态区之间的界面运动。CA模拟表明，界面向较低温度区域的运动是由全液体区域浓度的增加引起的。通过在CA模拟中将完全液体区域中的浓度更新为初始浓度以模仿液体中的有效搅拌，可以防止糊状区域和完全液体区域之间的界面移动。整个糊状区的模拟液体分数和平均浓度随时间降低，这与分析预测非常吻合。

图形概要