固液界面形貌及其转变

Characteristics of Solid-liquid Interface Patterns and Morphological Transitions

凝固时的固液界面通常为平面、胞状、枝晶状。在某些条件下结晶,会形成双胞结构、三胞结构、倾斜枝晶、密集分枝和退化枝晶等不规则界面。本文介绍了不规则界面的形貌特征,讨论了界面能各向异性、压力和温度对界面形貌的影响以及规则界面与不规则界面的相互转变等问题。当晶体沿着某些特定位向生长时,界面能接近于各向同性,晶体以密集分枝方式生长;当界面能各向异性时,大多数晶体以规则枝晶方式生长。在VF工艺中,低压下得到密集分枝界面;压力增加,界面以枝晶方式生长;压力进一步增加,重新得到密集分枝界面。

Commonly, solid-liquid interfaces are planar, colunmar or dendritic interfaces during solidification. But under some conditions, the solid-liquid interfaces are irregular interfaces, such as doublon structure, triplon structure, titled dendritic, dense branching morphology and degenerate dendrite pattern. The characteristics of the irregular solid-liquid interface morphology are summarized in this paper. The effects of anisotropy of surface tension, pressure and temperature on the interface patterns and the morphological transitions of regular and irregular solid-liquid interfaces are discussed. When the interface is growing along certain crystallographic directions, the surface tension is near isotropic, and the dense branching morphology will appear. Meanwhile, a regular and steady dendritic morphology could be formed only when the surface tension is anisotropic, which is true for the majority of materials under solidification. In the viscous fingering process, when the pressure is low, the interface is growing with dense branching morphology ; then as the pressure increases, the interface develops with the dendritic morphology; when the pressure further increases, the dense branching morphology is restored.