Growth Kinetics of Proeutectoid Ferrite in Fe-0.1C-1.5Mn-1Si Quaternary and Fe-0.1C-1.5Mn-1Si-0.2Al Quinary Alloys

The growth kinetics of proeutectoid ferrite in the early stages of transformation were studied in Fe-0.1C-1.5Mn-1Si (mass pct) quaternary and Fe-0.1C-1.5Mn-1Si-0.2Al quinary alloys. The observed kinetic transition temperatures from partitioned slow growth to unpartitioned fast growth of ferrite in both alloys are in good agreement with predictions using a local equilibrium model for multicomponent systems. The measured parabolic growth rate constants were smaller than those calculated assuming paraequilibrium in the unpartitioned growth region, but the difference between the measured and the calculated growth rate constants gradually diminished with a decreasing reaction temperature. The dissipation of driving force, derived from the diffusion of the substitutional solute within the transformation interface, possibly constitutes a major part of the discrepancy between the measured and the calculated growth kinetics.