The role of carbon diffusion in ferrite on the kinetics of cooperative growth of pearlite: A multi-phase field study

Cooperative growth of pearlite is simulated for eutectoid steel using the multi-phase field method. The model considers diffusion of carbon not only in γ phase, but also in α phase. The lamellar spacing and growth velocity are estimated for different undercoolings and compared with experimental results from the literature and theoretical results from analytical models. The important finding of this work is that carbon diffusion in ferrite and growth of cementite from the ferrite increase the kinetics of the pearlitic transformation by a factor of four as compared to growth from austenite only, which is assumed by the classic Zener–Hillert model. This growth mode therefore must be considered to be the dominating growth mode and it explains at least some of the differences between experiment and theory, where diffusion in ferrite is excluded.