Abstract In order to control macroscopic material properties, it is important to understand the fundamental mechanisms of microstructure evolution during solidification. Varying the solidification velocity in eutectic alloys can result in both a change in microstructural length scale and different patterns. In a structure consisting of rods or fibers aligned in the growth direction, the adjustment mechanisms for this kind of pattern evolution consist of merging and overgrowing events for coarsening, and splitting and nucleation events for refinement. To gain a better understanding of these mechanisms during three-dimensional ternary eutectic solidification, the distribution of these four types of events is quantitatively assessed using graph based analysis of a three-dimensional data set obtained by synchrotron tomography of a solidified ternary eutectic Al-Ag-Cu alloy. The results demonstrate that the amount of microstructural change events is larger for higher growth velocities. It is found that the microstructure adjustment under steady growth conditions, i.e. constant composition, constant solidification velocity and constant temperature gradient, is dominated by splitting and merging events, while the coarsening due to a velocity decrease occurs by rod termination via overgrowth. The comparison of the microstructure rearrangement of samples with different patterns and constant growth conditions show that, depending on the growth velocity, certain microstructure arrangements have a lower tendency to rearrange. The quantitative analysis of the rearrangement mechanisms lead to a better understanding of the microstructure evolution in complex eutectic alloys.

中文翻译：

---

基于图形的 Al-Ag-Cu 三元共晶定向凝固过程中三维组织重排研究

摘要 为了控制宏观材料的性能，了解凝固过程中微观结构演化的基本机制非常重要。改变共晶合金的凝固速度会导致微观结构长度尺度的变化和不同的图案。在由沿生长方向排列的棒或纤维组成的结构中，这种模式演化的调整机制包括合并和过度生长事件以进行粗化，以及分裂和成核事件进行细化。为了更好地了解三维三元共晶凝固过程中的这些机制，这四类事件的分布是使用基于图形的分析来定量评估的，该数据集是由凝固的三元共晶 Al-Ag-Cu 合金的同步加速器断层扫描获得的三维数据集。结果表明，对于较高的生长速度，微观结构变化事件的数量较大。发现稳定生长条件下的微观结构调整，即恒定成分、恒定凝固速度和恒定温度梯度，由分裂和合并事件支配，而由于速度降低导致的粗化发生在通过过度生长的棒终止。不同图案和恒定生长条件样品的微观结构重排的比较表明，取决于生长速度，某些微结构排列具有较低的重新排列趋势。重排机制的定量分析有助于更好地了解复杂共晶合金的微观结构演变。