The Square Root Diffusivity

9401044莫拉尔这个程序的目标是用基于严格的基本原理的简单方程来模拟复杂的扩散过程。对于单相和选定的多相体系，已经根据“平方根扩散系数”(一种材料的动力学属性)推导出了方程式。这些方程式对于正在学习复杂合金与二元合金的不同之处的学生以及从事合金和工艺设计工作的工程师都有价值。这些方程展示了如何测量复杂合金的平方根扩散系数，如何最小化互扩散速率和Kirkendall孔隙率，以及如何改变互扩散区中形成的相。一个结合电子探针和图像分析的镍基高温合金实验程序正被用来检验方程的准确性，并揭示与多组分、多相系统中扩散有关的新原理。%扩散会导致涂层涡轮叶片、金属基复合材料和其他高温使用材料的性能下降。此外，扩散在高温处理过程中也很重要，例如渗碳、渗碳和退火热处理。***

9401044 Morral The goal of this program is to model complex diffusional processes with simple equations that are based on rigorous, fundamental principles. Equations have already been derived for single and selected multiphase systems in terms of the "square root diffusivity," a kinetic property of materials. The equations have value to students who are learning how complex alloys differ from binary alloys and to engineers working on alloy and process design. The equations show how to measure the square root diffusivity of complex alloys, how to minimize interdiffusion rates and Kirkendall porosity, and how to vary the phases that form in interdiffusion zones. An experimental program combining electron microprobe and image analysis of nickel-base superalloys is being used to test the accuracy of the equations and to uncover new principles related to diffusion in multicomponent, multiphase systems. %%% Diffusion causes property degradation in coated turbine blades, metal-matrix composites, and other materials used for high temperature service. In addition, diffusion is important during high temperature processing, for example, pack cementation, carburizing and annealing. ***