Abstract.

The mechanisms by which interfacial instabilities instigate the growth of solidification patterns is a topic of longstanding interest. In columnar solidification of metallic melts, where the solid-liquid interfacial energy is anisotropic, evolving dendritic patterns compete depending on their relative misorientation. By contrast, organic “plastic crystals”, such as alloys based on succinonitrile, where the anisotropy in their solid-liquid interfacial energy is extremely weak, solidify forming seaweed patterns that typically exhibit little, if any, growth competition. We explore in this study mechanisms by which columnar solidification microstructures of binary alloys with low crystalline anisotropy compete. We adopt toward this end a validated Navier-Stokes multiphase-field approach to characterize the influence of grain misorientation, seed morphology, and melt advection on the growth competition. Simulated seaweed patterns indicate profound influences of all three factors, although characteristic solidification morphologies are observed to evolve depending on the melt flow intensity.

Graphical abstract

中文翻译：

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海藻微结构的柱状凝固过程中的增长竞争：3-D相场模拟的见解。

摘要。

界面不稳定性促使凝固模式增长的机制是长期关注的话题。在金属熔体的柱状凝固中，固液界面能是各向异性的，根据它们的相对取向不良，演化的树枝状晶会竞争。相比之下，有机“塑料晶体”（例如基于丁二腈的合金）的固液界面能中的各向异性非常弱，它们会固化形成海藻图案，这些图案通常显示出很少的竞争（如果有的话）。我们在这项研究中探索了具有低结晶各向异性的二元合金的柱状凝固微观结构竞争的机理。为此，我们采用经过验证的Navier-Stokes多相场方法来表征晶粒取向不良的影响，种子的形态，以及对流平流对生长的竞争。尽管观察到特征性的凝固形态会根据熔体流动强度而发展，但模拟的海藻图案表明了这三个因素的深远影响。

图形概要