Modeling kinetics of the austenite simultaneous decomposition into two bainitic products in the range of swing back

A model of bainite transformation for two simultaneous reactions in the range of swing back is presented. The bainitic microstructure includes two different sheaves. The sheaves of first type had a midrib in the direction of the plates axes and form a butterfly shape. The second type of sheaves were of the grain boundary nucleated bainite. A mathematical model permitted dividing the kinetic curves and establishing separate time-temperature-transformation (TTT) diagrams for the individual structural components. The experimental data were obtained from dilatometric experiments. The assumptions of the model consist of the exponential relationship of the volume of the individual sub-plates and the autocatalytic coefficients related to the changes of nucleation rates. The results of the computation showed that the lengths of the individually formed sub-plates are dependent on the type of the structural component.