Previous research had suggested that the binding energy of C–vacancy complexes was of the order of 35 to 55kJ/mol in face-centered cubic Fe-based alloys. In addition to point-defect anelasticity, data on the self-diffusion of Fe in face-centered cubic Fe were quantitatively consistent with the present results on point-defect structure modeling. Quenching, cold working and electron irradiation increased the height of the damping peaks which were associated with C motion. This was consistent with a contribution of C–vacancy complexes to the relaxation strength of the peaks. The effect of increasing the C content, upon Fe self-diffusion in face-centered cubic Fe, was to decrease the activation energy for self-diffusion and increased the diffusivity. This implied a C-vacancy binding energy of about 40kJ/mol. First-principles gradient-corrected density functional calculations were used to determine directly the binding energy of nearest-neighbor C–vacancy pairs in face-centered cubic Fe. A value of about 35kJ/mol was obtained.

Carbon–Vacancy Interactions in Austenitic Alloys. J.A.Slane, C.Wolverton, R.Gibala: Materials Science and Engineering A, 2004, 370[1-2], 67-72