Molecular dynamics study of carbon diffusion in austenite

The molecular dynamics method is applied to investigate carbon interstitial diffusion in austenite at low carbon content. An approximation that carbon atoms can interact with each other only indirectly (via neighbouring iron atoms) is used. Sets of Arrhenius parameters of interstitial carbon jump frequencies identified by the four-frequency model are determined. Comparison of the molecular dynamics results with experimental data analysis in the context of the four-frequency model is performed. It is shown that the four-frequency model may not be adequate to describe the carbon diffusion process. To improve the analytical model the specific role of the transition probabilities during association and dissociation of the first nearest neighbour carbon pairs through the second neighbour sites should be considered. The direct repulsion between the carbon first neighbour positions should be also taken into account in molecular dynamics simulation.