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arXiv 1605.05005cond-mat.mtrl-sci
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纯物质和二元材料的平面界面不稳定性和固液界面扩散

Interfacial instability of a planar interface and diffuseness at the solid-liquid interface for pure and binary materials

Yaw Delali Bensah, J. A. Sekhar

摘要:

随着凝固速率的变化,会发生形貌和扩散界面的重构。在这篇文章中,我们追求的假设,在凝固过程中的界面配置是由严格的固体和严格的液相之间的区域的熵产生率。我们认为,当一个接口开始迁移时,有几种稳定的配置是可能的。这些包括原子平面、扩散平面、小平面非平面和蜂窝非平面。提供最大熵产生率(MEPR)的配置和地形条件产生最稳定的界面配置。MEPR的原理应用于(1)描述原子级光滑和扩散界面,(2)提供扩散界面厚度和界面区域中伪原子层的数量的定量结果,以及(3)预测作为凝固速度或温度梯度的函数的从平面到非平面小面或非小面胞状形态的转变。60多年来的大量实验研究未能全面验证任何现有的固液界面(SLI)生长不稳定性模型。与MEPR模型,第一次,击穿条件的预测具有相当程度的准确性,为一些二元合金,没有以前的理论模型具有可预测性。该模型考虑稳态凝固在接近和远离平衡条件。

英文摘要:

Topographical and diffuse interface reconfigurations occur with a change in the solidification rate. In this article we pursue the hypothesis that the interface configuration during solidification is determined by the rate of entropy production in the region between a rigorous solid and rigorous liquid phase. We posit that when an interface begins to migrate, there are several stable configurations that are possible. These include atomistically-planar, diffuse-planar, facet non-planar and cellular non-planar. The configuration and topographical condition that affords the maximum entropy production rate (MEPR) yields the most stable interface configuration. The principle of MEPR is applied to (1) describe atomistically smooth and diffuse interfaces, (2) provide quantitative results for the diffuse interface thickness and the number of pseudo-atomic layers in the interface region, and (3) predict the transition from planar to a non-planar facet or non-facet cellular morphology as a function of solidification velocity or temperature gradient. Numerous experimental investigations spanning over sixty years have failed to comprehensively validate any of the existing solid-liquid interface (SLI) growth instability models. With the MEPR model, for the first time, breakdown conditions are predicted with a fair degree of accuracy for a number of binary alloys where no previous theoretical model had predictability. The model considers steady state solidification at close-to and far-from equilibrium conditions.

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