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

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