The effects of interface kinetics anisotropy on the growth direction of cellular microstructures
The effects of interface kinetics anisotropy on the growth direction of cellular microstructures
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DOI：
10.1007/bf02656826
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发表时间：
1991-02
期刊：
影响因子：
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通讯作者：
R. Trivedi;V. Seetharaman;M. Eshelman
中科院分区：
文献类型：
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作者：
R. Trivedi;V. Seetharaman;M. Eshelman
在戊酸-乙醇体系中进行了定向凝固研究，其中界面动力学和界面自由能存在显著的各向异性。这些各向异性影响微观结构的形成，并经常导致细胞和枝晶的形成，这些细胞和枝晶相对于热流方向倾斜。结果表明，晶胞的倾斜角度是由热流和晶体各向异性的相对作用决定的。对于给定的晶体方向，这个倾斜角随着速度的增加而增加。当细胞生长方向与首选晶体学方向重合时，倾斜角度达到最大。， <001<方向为立方戊酸晶体。此时，细胞形态向树突形态转变。对于稳态细胞结构，研究了倾斜角随速度的变化。然后将这些结果与平面界面稳定性的线性和弱非线性分析进行比较，以获得动力学各向异性效应的大小。在相同的生长速率、温度梯度和成分条件下，细胞间距和细胞振幅随倾斜角度的变化有显著的变化。
Directional solidification studies have been carried out in the pivalic acid-ethanol system in which significant anisotropies in interface kinetics and interfacial free energy are present. These anisotropic properties influence the microstructure formation and often lead to the formation of cells and dendrites which are tilted with respect to the heat flow direction. It is shown that dendrites always form in the preferred crystallographic direction, whereas the angle of tilt for cells is governed by the relative effects of heat flow and the anisotropic property of the crystal. This tilt angle for a given crystal orientation is found to increase as the velocity is increased. The angle of tilt reaches its largest value when the cell growth direction coincides with the preferred crystallographic direction,i.e., <001< direction for the cubic pivalic acid crystals. At this point, a transition from cellular to dendritic morphology occurs. The variation in the angle of tilt as a function of velocity is examined for the steady-state cellular structures. These results are then compared with the linear and the weakly nonlinear analyses of the planar interface stability to obtain the magnitude of the kinetic anisotropy effects. It is also shown that the cellular spacings as well as the amplitude of cells alter significantly with the angle of tilt under identical conditions of growth rate, temperature gradient, and composition.