1. Kinetic Parameters and Activation Energy of Pearlitic and Bainitic Transformations Calculated by Analyzing the TTT Diagrams of Undercooled Austenite

Based on the analysis of the experimental C-shaped TTT diagrams of undercooled austenite, the study proposes a method for calculating the kinetic parameters of the Avrami equation and for determining the activation energy for pearlitic and bainitic transformations. To this effect, upon the TTT curve digitization, the kinetic curves were plotted for the volume fraction of undercooled austenite at different transformation temperatures. Case-specific n and A parameters were calculated for the Avrami equation. Temperature dependence of the A parameter makes it possible to determine the activation energy for pearlitic and bainitic transformations. The temperature dependence of activation energy is shown to be fitted with a hyperbolic curve. An equation is suggested to describe the activation energy as a function of austenite supercooling. The parameters thus obtained make it possible to describe the temperature time kinetics of the pearlitic and bainitic transformations.