Abstract We carry out three-dimensional phase-field simulations to model unique experimental observations of cellular and dendritic solidification structures formed under diffusive growth conditions in the DSI (Directional Solidification Insert) of the DECLIC (DEvice for the study of Critical LIquids and Crystallization) aboard the International Space Station. We had previously shown experimentally that complex thermal conditions affect the stationary position of the solid-liquid interface, as well as its dynamics of relaxation towards this stationary position over a finite time after the onset of sample pulling. Here, we discuss the effects of thermal diffusion within the adiabatic zone of the directional solidification setup and of latent heat release at the solid-liquid interface by means of quantitative phase-field simulations. Simulations and experiments characterize the entire evolution of the primary spacing of cellular/dendritic array structures from the onset of morphological instability to the establishment of the final steady-state spacing, including the transient coarsening regime associated with a sharp increase of spacing. Accounting for these thermal effects leads to a major improvement in the agreement between simulations and microgravity measurements for both the time of occurrence of morphological instability after the start of the experiment and the subsequent spacing evolution, which are not accurately predicted using the standard frozen temperature approximation.

中文翻译：

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合金定向凝固过程中热场对界面动力学和微观结构选择的影响

摘要 我们进行了三维相场模拟来模拟在 DECLIC（临界液体和结晶研究设备）的 DSI（定向凝固插入物）中在扩散生长条件下形成的细胞和树枝状凝固结构的独特实验观察。国际空间站。我们之前已经通过实验表明，复杂的热条件会影响固液界面的固定位置，以及在样品拉动开始后的有限时间内其向该固定位置的松弛动力学。在这里，我们通过定量相场模拟讨论了定向凝固装置绝热区内的热扩散和固液界面潜热释放的影响。模拟和实验表征了细胞/树突阵列结构的主要间距从形态不稳定开始到最终稳态间距建立的整个演变，包括与间距急剧增加相关的瞬态粗化机制。考虑到这些热效应，在实验开始后形态不稳定的发生时间和随后的间距演变方面，模拟和微重力测量之间的一致性得到了重大改进，使用标准冻结温度近似值无法准确预测.