The Square Root Diffusivity

这项研究的目标是用简单但严格的方程来模拟复杂的扩散过程。对于单相系统，这些方程已经用平方根扩散系数的形式推导出来。为了满足扩散系数恒定的假设，用含有小浓度差的扩散偶进行了实验研究。正在开发一种计算机程序来预测扩散偶中的浓度分布，该扩散偶包含多达8种合金元素。该研究对高温渗碳、氧化、退火等高温加工工艺具有重要意义。在涂层涡轮叶片和金属基复合材料等高温材料系统中，扩散会导致性能退化。这项研究应该为这些和类似的过程提供有价值的预测能力。

The goal of this research effort is to model complex diffusional processes with simple, but rigorous equations. These equations have already been derived for single phase systems in terms of the square root diffusivity. Experimental studies are made using diffusion couples containing small concentration differences in order to satisfy a constant diffusivity assumption. A computer program is being developed to predict concentration profiles in diffusion couples that contain up to eight alloying elements. This research is important to high temperature processing techniques such as pack cementation, oxidation and annealing. Diffusion causes property degradation in high temperature materials systems such as coated turbine blades and metal-matrix composites. This research should provide valuable predictive capabilities for these and similar processes.