Modelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity, and coarsening

The growth of niobium carbide in austenite involves the diffusion of both niobium and carbon. These elements diffuse at very different rates. A model is presented for the overall transformation kinetics of niobium carbide precipitation in austenite that takes into account the multicomponent nature of the diffusion process while at the same time allo,vs for the curvature of the transformation front. The inclusion of the curvature (capillarity) effect has, in a numerical scheme, permitted the precipitation and coarsening reactions to be treated in a single model. The model is compared with published experimental data.