Chemo-mechanical coupling effect on bidirectional diffusion process during oxidation

Abstract

The chemo-mechanical coupling effect has been widely investigated due to its important impact on many areas, such as Li-ion batteries, biomechanical engineering, hydrogen embrittlement, etc. Meanwhile, the chemo-mechanical coupling effect on the high temperature oxidation process is drawing increasing attention. During oxidation, stress can be induced in the oxide film and will in turn influence the diffusion process and oxidation kinetics. Understanding the coupling effect between stress and oxidation helps to illuminate the mechanism of material degradation and failure. In this work, a concise physical model is developed for oxidation kinetics at elevated temperatures considering the diffusion-stress coupling effect, where both the inward and outward diffusion are considered. The model prediction shows an excellent agreement with the experimental observation. Based on this physical model, we also proposed a parameter to characterize the effects of cation/anion diffusion as well as a phase diagram to describe the universal diffusion–oxidation growth process.