Simulation of TiC Precipitation in Ti-added Low Carbon Steel

Precipitation of TiC from austenite or ferrite in Ti-added low carbon steels is simulated using an N-model. The time-dependent nucleation rate is calculated from classical nucleation theory, assuming that nucleation occurs preferentially along dislocations and the critical nucleus is a parallelpiped with {100}TiC facets. The growth rate is calculated using the mean field approximation assuming that the transport of solute (Ti) along dislocations accelerates the growth. Results show that at the first stage precipitation proceeds rapidly almost to the final volume fraction. Then, the precipitation enters the second stage in which neither the particle density nor the size vary appreciably, which continues quite a long time until the particle density begins to decrease, i.e. coarsening begins (the third stage). From comparison with isothermal holding experiments conducted at 1000°C for austenite and 580°C for ferrite, the precipitate/matrix interfacial energy which includes the interaction of a nucleus with the strain field of dislocation is evaluated to be 0.20–0.25 J/m2 for austenite, which are comparable with the values reported by other authors, whereas it is 0.35–0.50 J/m2 for the side facet of a TiC particle in ferrite.