A kinetic 10-frequency model for interstitial diffusion via octahedral interstices in a face-centred cubic lattice was developed. The specific role of the transition probabilities during the association and dissociation of the first-nearest neighbour interstitial pairs via the second-nearest neighbour sites was considered. The model was applied to C diffusion in austenite. Molecular dynamics was used to investigate C interstitial diffusion at low C-contents. The assumption that C atoms could interact with each other only indirectly (via neighbouring Fe atoms) was made. The Arrhenius parameters of interstitial C jump frequencies which were consistent with the 10-frequency model were determined. A comparison of the molecular dynamics results was made with experimental data at 1273K within the context of the 10-frequency model. It was shown that a small direct repulsion between C atoms at first-nearest neighbour sites should be included. It was found that the initial increase (with increasing C content) in both the tracer and chemical diffusion coefficients was a result of increased rates of dissociation of C, from first- and second-nearest neighbour pairs to third-nearest neighbour sites.

Kinetic and Molecular Dynamics Analysis of Carbon Diffusion in Austenite. A.V.Evteev, E.V.Levchenko, I.V.Belova, G.E.Murch: Philosophical Magazine, 2007, 87[28], 4335-57