The Square Root Diffusivity

小行星9401044 该计划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。 方程已经推导出单一和选定的多相系统的“平方根扩散率”，材料的动力学性质。 这些方程对正在学习复杂合金与二元合金的区别的学生以及从事合金和工艺设计的工程师都有价值。 该方程显示了如何测量复杂合金的平方根扩散率，如何最大限度地减少相互扩散速率和Kirkendall孔隙率，以及如何改变在相互扩散区形成的相。 结合电子探针和图像分析的镍基高温合金的实验程序被用来测试方程的准确性，并揭示新的原则，多组分，多相系统中的扩散。 %扩散会导致涂层涡轮机叶片、金属基复合材料和用于高温应用的其他材料的性能下降。 此外，扩散在高温处理期间是重要的，例如，包埋渗、渗碳和退火。 ***

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. ***