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利用有限差分法对定向凝固初始过渡区的溶质再分配、凝固界面位置以及凝固速度进行了定量计算,重点分析了温度梯度的影响。计算结果表明:初始过渡区存在凝固速度、凝固界面位置的非稳态过程,温度梯度越小,非稳态过程越长;温度梯度较小时,凝固速度数值计算结果与Fu等提出的指数形式有很大偏离;初始过渡区晶锭组分分布的数值解与Tiller近似解偏离较大,Tiller近似解所给出的溶质初始过渡区长度偏小;晶锭组分初始不均匀区的长度与凝固速度非稳态过程的长短有关;初始过渡区凝固界面向低温区的移动使凝固时间显著加长。
Solute redistribution, solidification interface and solidification rate in the initial transition zone of directional solidification were quantitatively calculated by finite difference method. The influence of temperature gradient was analyzed emphatically. The calculation results show that the initial transition region has the instability process at solidification interface and solidification interface. The smaller the temperature gradient, the longer the non-steady state process. When the temperature gradient is small, the numerical results of the solidification speed are similar to the exponential forms Deviate greatly from the numerical solution of the ingot component distribution in the initial transition zone and the Tiller approximate solution, the length of the solute initial transition zone given by the Tiller approximation solution is too small, and the length and solidification of the initial inhomogeneous zone of the ingot component The speed of the unsteady process is related to the length of the initial transition zone freezing zone to the low temperature zone so that the solidification time significantly longer.