**3. Modeling of Austenite–Ferrite Transformation Kinetics**

Over the past few decades, extensive research has been devoted to the study of austenite–ferrite transformation kinetics. Among the several proposed theories, diffusion-controlled theory is the most important one. For the Fe-C-M (M stands for the substitutional element) system, there are two proposed thermodynamic equilibrium conditions, i.e., para equilibrium (PE) and local equilibrium (LE).
