Discussions on the correlation between thermodynamics and kinetics during the phase transformations in the TMCP of low-alloy steels

Thermo-mechanical control process (TMCP) plays a key role in the manufacturing of hot-rolled low-alloy steels, as well as the optimization of microstructures and properties. However, the various phase transformations involved in the TMCP of steels and its impact on the microstructures/properties are still not fully understood. In the present work, on the basis of classical theories of phase transformations and previous experimental results, the key parameters controlling the phase transformation processes are analyzed, from which the correlation between thermodynamics and kinetics of the phase transformations are proposed; then, this correlation in the phase transformations of low-alloy steels and its effect on the competing mechanisms of transformations are analyzed; based on well-established theories (i.e. the first-principles calculations and the double well potential in phase field methods), the energetics of the Bain path of Na and the fcc/bcc transformation of Fe are calculated to demonstrate the correlation between thermodynamics and kinetics. Eventually, the current work is summarized and the potential applications of the correlation between thermodynamics and kinetics of phase transformations are proposed.