The ion-beam mixing of SiC-coated Fe, Cr, Ni, Cu, and stainless steel was investigated, by means of Auger electron spectroscopy, to determine the role of thermodynamics in the process. Both inert (Ar') and reactive (N') ions were used at either 30 keV or 160keV incident energy. A mechanism involving thermally activated motion of bombardment-induced defects appeared relevant to the onset of a chemical bias in the mixing. Further, the formalism established for describing ion mixing, based on Darken's analysis of chemical interdiffusion coefficients, provided a quantitative interpretation of the results.