单相合金凝固过程时间相关的界面稳定性(I)理论分析

对定向凝固界面前沿非稳态溶质扩散场进行了系统的对比分析，发现无论在纯扩散还是存在对流的情况下，界面前沿的溶质扩散场通常满足指数分布的形式，可以采用一个统一的公式来描述界面前沿的瞬态溶质扩散场.进而在此基础上，对定向凝固界面形态稳定性进行了统一的时间相关的非稳态分析，发现界面临界稳定性条件的数学描述形式与Mullins和Seker ka理论给出的稳态解完全一致, 只是用时间相关的浓度梯度GtC、界面速度Vi、溶质扩散长度l代替了稳态生长中所得到的GC,V，DL/V.

Time-dependent interface stability during directional solidification of a single phase alloy(Ⅰ) Theoritical

The initial transient solute redistribution during directional solidification is systematically investigated by carefully comparing the current theoreltical models with experimental results. It is shown that at the transient front solute redistribution generally meets an exponential profile no matter whether there exists liquid convection or pure diffusion in front of the liquid/solid interface.The profile can be described by a unified formula. Based on this, a general time-dependent linear dynamic analysis of the morphological instability of a solidifying planar interface during directional solidification is carried out. It is found that the time-dependent instability solution has the same form as the steady-state solution described by Mullins and Sekerka, but the time-dependent concentration gradient G t C, interface velocity V i and diffusion length l should replace the corresponding steady-state concentration gradient G C,interface velocity V,diffusion length D L/V in Mullins and Sekerka solution.