ANALYSIS OF THE γ → α TRANSFORMATION IN A C-MN STEEL BY DILATOMETRY, LASER SCANNING CONFOCAL MICROSCOPY AND PHASE FIELD MODELLING

摘要

This paper deals with the kinetics of the austenite to ferrite (γ → α) transformation during controlled cooling of C-Mn steel. A phase field model is used to simulate the γ → α transformation. The coupled differential equations governing the phase field development, characterising the phase of the system at each point in space and time, and the solute diffusion are presented. The numerical solution of the equations yields the time evolution of the microstructure. The γ → α transformation kinetics is also investigated experimentally, using dilatometry and laser scanning confocal microscopy. A remarkably good agreement between the experimental and simulated development of the phase fractions, as a function of temperature and time, is obtained using realistic values for the physical material parameters featured in the model. Moreover, the simulated microstructure is shown to have the same characteristics as the experimental one. The interface velocity is investigated in more detail.