**4. Conclusions**

The results of this study clearly show the effect of the heating rate and initial microstructure on the nucleation and growth of austenite during intercritical and supercritical temperature. In ferrite-pearlite microstructures, slower heating rates, nucleation and growth reactions are preferred. Fast heating rates have a strong influence on the carbide dissolution during intercritical and supercritical annealing treatments. The transformation behavior of austenite after supercritical annealing at small Δ*T* (*T-TAc3*) and fast cooling rates always resulted in a multi-phase complex microstructure. At higher Δ*T*'s a duplex microstructure with more martensite and less bainite was observed. The PAGS was not strongly influenced by fast heating rates and short holding times. The best combination of mechanical properties was obtained at small Δ*T* when the balance of martensite and bainite was optimum.

**Author Contributions:** All the authors contributed to this work. J.P.P. obtained his M.Sc. degree with this work; R.L.-M. conducted the EBSD-IQ and SEM analysis; O.G.-R. performed the mechanical testing; and C.I.G. was the academic advisor and wrote the manuscript.

**Acknowledgments:** The authors would like to thank TERNIUM-MEXICO for providing the commercial samples used on this study and the financial support. Also the authors would like to thank the members of the Ferrous Physical Metallurgy-MEMS Department at the University of Pittsburgh for their support.

**Conflicts of Interest:** The authors have not conflict of interest.
