Internal oxidation of metastable metallic materials

Abstract

Abstract The special kind of internal oxidation phenomenon that can take place in pure metals containing a high concentration of defects, particularly thermodynamically stabilized vacancy clusters, is presented. The process starts with dissolution of oxygen into the metal at the free surfaces and continues with diffusion of oxygen atoms into the volume of the metal matrix where they are trapped at numerous defects in the crystal lattice. The increasing oxygen activity at these places causes local oxidation of the matrix and consequently precipitation of fine oxide particles. The results of experimental studies performed with pure copper metal confirmed the formation of microstructures consisting of continuous three-dimensional copper matrix and homogeneous finely dispersed Cu2O particles of submicron size. The volume fraction of precipitated oxides depends on the starting microstructure of the Cu matrix, and on the temperature and time of the internal oxidation process.