Model for estimation of transformation kinetics from the dilatation data during a cooling of hypoeutectoid steels

The purpose of this paper is to depict a method for quantitatively relating the dilatation curves to the proeutectoid ferrite and the pearlite transformation kinetics during a continuous cooling of the hypoeutectoid steels. If the volume fractions of phases can be quantitatively related to the dilatation data, the dilatometric technique may be efficiently applicable to the investigation of the phase transformation kinetics. In the present work, a model directly extracting the information of the proeutectoid ferrite and the pearlite transformation from the dilatation curve for the hypoeutectoid steels was developed. The volume fraction of the phases was calculated from the dilatation curve by using the linear thermal contraction coefficients, the lattice parameters and the compositions of phases under the paraequilibrium condition. The proposed model was based on the carbon enrichment of the austenite and the difference in unit volume of phases during the phase transformation. The model was applied to the determination of the phase transformation kinetics from the dilatation curves and verified by comparing the model results with the experimental results of the hypoeutectoid steels. It was shown that there were excellent agreements between the calculation results and the experiments results. (C) 2003 Elsevier B.V. All rights reserved.