A Model for Oxide Film Evolution on Alloys and Prediction of Resulting Layer Structure

Abstract

Alloys and their oxides are a very important class of materials on which modern society depends. Yet, today we do not have an adequate fundamental physical-chemical model of how oxides evolve on alloys under oxidizing conditions. This physical chemical understanding will effect our ability to design a wide range of materials from electronic devices to the improved protective oxide films on alloys. The fundamental progress, in both physics and chemistry, made on several critical questions, •What interface(s) control alloy oxidation and how? •What parameters provide the driving potential for oxidation? •How does this potential respond to temperature (T), pressure (P) and compositional changes? will be discussed. Progress on these questions have allowed models to be proposed to predict alloy oxidation behavior under any set of conditions. These models are already providing some predictive power in how the oxide overlayer and passive film structure develop. By using surface studies of the oxidation behavior of the following alloys and their thin films: Cu-Mn, Ag-Mn, Ni-Ti, Ni-Zr, Ti-Cu and Ti-Al, we have been able to delineate the factors which are most important to the oxide formation process and provide insight into the prediction of oxide layer structures. These will be illustrated with actual experimental results on selected alloys.