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本文根据固液界面溶质非平衡分配的实验现象[1-5],首次分析了溶质非平衡分配对凝固理论中最简单而又具有特别重要意义的成分过冷理论的影响。提出固液界面偏离平衡的程度可以由界面过冷度△T=△T_k+△T_n来表示,其中△T_k是动力学过冷度,△T_n是溶质非平衡分配造成的附加界面过冷度。三十多年来冶金学界和物理学界广泛接受的一个重要概念,即平界面失去稳定性是界面前液相中存在成分过冷区的结果,本文已指出其错误,并指出凝固驱动力沿界面前进方向增大是平界面形态不稳定性的真正原因。从这个原理出发,完全不需要界面局域平衡假定,导出了与传统的成分过冷理论关于平界面稳定性的判据在形式上完全相同的新判据G/V≥mC_0(k—1)/kD其中仅仅是用实际溶质分配系数k取代了平衡溶质分配系数k_0。这个新判据得到了Al-C_u合金实验[1]的支持。
Based on the experimental phenomena of the unbalanced solute distribution at the solid-liquid interface [1-5], the effect of the non-equilibrium distribution of solute on the theory of subcooling, the simplest and most important component of the solidification theory, is analyzed for the first time. It is proposed that the degree of deviation of the solid-liquid interface from equilibrium can be expressed by the interface undercooling ΔT = ΔT_k + ΔT_n, where ΔT_k is the kinetic undercooling and ΔT_n is the additional interface undercooling caused by the unbalanced solute imbalance. An important concept universally accepted by the metallurgy and physics circles for more than thirty years is that the flat interface loss stability is the result of the presence of undercooling in the liquid phase before the interface. This paper has pointed out the errors and pointed out that the solidification driving force along the interface The increase of the forward direction is the real reason for the instability of the flat interface. Based on this principle, we do not need the interface local equilibrium hypothesis at all, and the new criterion G / V≥mC_0 (k-1) is derived which is completely identical with the traditional theory of composition undercooling criterion. / kD where only the equilibrium solute partition coefficient k_0 is replaced by the actual solute partition coefficient k. This new criterion has been supported by Al-C_u alloy experiment [1].