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以丁二腈-丙酮合金为研究对象,采用Mach-Zehnder光学显微干涉仪对其定向凝固平界面前沿非稳态溶质扩散场的演化行为进行了定量研究,通过水平定向凝固和垂直定向凝固方法,分析了不同凝固方式对界面前沿溶质场分布的影响。结果表明:水平定向凝固时,自然对流的存在,使固液界面首先在重力方向上失稳,固液界面不是垂直的平界面而是呈现为一个楔形的曲面,生长时溶质容易富集于楔形固液两相区;垂直定向凝固时,界面向上生长的溶质扩散边界层厚度要小于界面向下生长的溶质扩散边界层厚度,分别为0.6 mm和1.0 mm左右,界面前沿的溶质场分布与Warren-Langer溶质纯扩散模型的预测值相差较大,却比较接近林鑫等所发展的考虑对流作用下的溶质再分配半解析数值模型预测值。
In this paper, the evolution behavior of unsteady solute diffusion field at the frontal interface of directional solidification was investigated by using Mach-Zehnder optical microscopy interferometer with succinonitrile-acetone alloy as the research object. Through horizontal directional solidification and vertical directional solidification The effects of different solidification methods on the solute field distribution at the front of the interface were analyzed. The results show that in the horizontal directional solidification, the existence of natural convection causes the solid-liquid interface to first instability in the direction of gravity, the solid-liquid interface is not a vertical flat interface but a wedge-shaped curved surface, and the solute tends to be enriched in the wedge Solid-liquid two-phase zone. When the vertical directional solidification is performed, the thickness of solute diffusion boundary layer growing upwards is smaller than that of the solute diffusion boundary growing downwards by 0.6 mm and 1.0 mm, respectively. The solute field distribution at the front of the interface is similar to that of Warren -Langer pure solute diffusion model predictive value difference is quite large, but nearer to the development of Lin Xin et al. Considering the convection effect of solute redistribution semi-analytical numerical model predictive value.