An atomistic model for the graphite–alumina/liquid iron system: Monte-Carlo simulations on carbon dissolution

A Monte-Carlo (MC) simulation study has been carried out at 1600 °C on graphite-alumina/liquid iron system with an aim to develop an atomistic model with optimum interaction parameters. The atomistic model of the graphite/liquid iron system was extended to include alumina molecules in the solid graphitic lattice. A molecule of alumina was represented as a rigid unified group of five atoms and occupied five neighbouring lattice sites. Using a canonical ensemble, simulations were carried out for a range of compositions and alumina interaction parameters. As non-wetting of alumina by liquid iron was expected to significantly affect carbon dissolution from graphite-alumina mixtures, interaction between alumina and iron was assumed to be strongly repulsive. Dissolution of carbon from alumina-graphite into liquid iron was monitored and compared with the experimental results. Even for a wide choice of alumina interaction parameters, it was not possible to get a good fit between simulation and experimental results. Another attempt was made to incorporate non-wetting at an atomic level by modifying the nature of interactions on the solid/liquid interface. While these simulations produced a much better agreement with experiment, some gaps still persisted at high alumina concentrations. A third attempt was then made to simulate non-wetting behaviour in terms of mutual exclusion of alumina and iron from their immediate neighbourhood. An excellent fit was obtained with experimental results in the entire composition range. In addition, alumina interaction parameters were found to have no effect on carbon dissolution and were therefore redundant. The optimum interaction parameters for the graphite-alumina/liquid iron system are: J1(C-C) = -J,J1(C-Fe) = 0.6J,J1(Fe-Fe) = J and no interaction parameters for alumina.