Influence of Morphological Instability on Grain Boundary Trajectory During Directional Solidification
Influence of Morphological Instability on Grain Boundary Trajectory During Directional Solidification
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DOI：
10.2139/ssrn.3315654
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发表时间：
2019-01
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影响因子：
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通讯作者：
Supriyo Ghosh;A. Karma;M. Plapp;S. Akamatsu;S. Bottin-Rousseau;G. Faivre
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文献类型：
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作者：
Supriyo Ghosh;A. Karma;M. Plapp;S. Akamatsu;S. Bottin-Rousseau;G. Faivre
通过透明合金薄试样定向凝固实验和二维相场法数值模拟，研究了凝固前沿扩散控制动力学与固液界面晶界沟槽轨迹之间的相互作用。我们发现，低角度晶界（亚边界）与各向异性的界面自由能生长在一个角度$\theta_t$相对于温度梯度轴倾斜。只要凝固速度V保持较低，$\theta_t$就基本上保持等于其在平衡时施加的值。当$V$增加并接近细胞不稳定阈值时，$\theta_t$减小，并最终在稳态细胞形态形成时消失。固体中亚边界的流动性的缺乏是这种转变的关键。这些发现是在很好的协议与最近的线性稳定性分析的问题。
The interplay between the diffusion-controlled dynamics of a solidification front and the trajectory of a grain boundary groove at the solid-liquid interface is studied by means of thin-sample directional solidification experiments of a transparent alloy, and by numerical simulations with the phase-field method in two dimensions. We find that low-angle grain boundaries (subboundaries) with an anisotropic interfacial free energy grow tilted at an angle $\theta_t$ with respect to the temperature gradient axis. $\theta_t$ remains essentially equal to its value imposed at equilibrium as long as the solidification velocity $V$ remains low. When $V$ increases and approaches the cellular instability threshold, $\theta_t$ decreases, and eventually vanishes when a steady-state cellular morphology forms. The absence of mobility of the subboundary in the solid is key to this transition. These findings are in good agreement with a recent linear-stability analysis of the problem.