A Model for the Calculation of the Bainitic Phase Transformation Kinetics from Dilatometric Data

The development of a method for determining phase transformation kinetics for a multistep solid-state transformation from a dilatation curve is described. The dilatation of steels during a continuous cooling or an isothermal holding of an austenite is analyzed. A model is proposed in which the transient dilatation is calculated based on the fraction of the phases present. The model can be applied to calculate the phase transformation kinetics from a dilatation curve of a hypo-eutectoid steel. After verification by comparison with experimental results for an interstitial-free steel, the model is used to calculate the transformation kinetics indicated by the dilatation curves of a bainitic grade steel. Excellent agreement between the model and experiments has been obtained.