MODELING OF OXIDATION IN METAL-MATRIX COMPOSITES

Oxidation in metal matrix composites (MMCs) is modeled by Fickian diffusion of oxygen in both the oxide layer and metal matrix. The oxidation process and the resulting immobilized oxygen at the interface is accounted for by the introduction of a jump discontinuity in the oxygen concentration across the interface. The problems of a uniformly growing oxide layer from the surface of a semi-infinite solid, outward oxygen diffusion and oxidation from a cylindrical cavity, as well as inward oxygen diffusion and oxidation from the surface of a cylinder, are considered as benchmark problems in oxidation of MMCs. In addition to the modeling results, a series of experimental results of oxidation of a unidirectional SiC/Ti matrix MMC are presented. The measured oxide thicknesses at different times and temperatures are used to calibrate and validate the model under development. While the present paper deals only with the oxidation problem, the coupled oxidation-thermomechanical problem, and especially the influence of oxidation on fatigue life of MMCs, will be presented in a future communication.