Thermodynamic and kinetic analysis of dynamic strain-induced transformation during hot deformation in plain carbon steels

Thermodynamic and kinetic analysis of dynamic strain-induced transformation (DSIT) is presented in this paper. Thermodynamic analysis indicates that DSIT above the Ae3 could not be massive transformation because the required stored energy is higher than that accumulated by hot deformation. Numerical simulations on ferrite growth kinetics indicate that ferrite nuclei can quickly grow to a size of more than 1 μm at a temperature just above the Ar3 when paraequilibrium is maintained at the γ/α interface, suggesting that paraequilibrium is the most possible mechanism for DSIT.

► Mechanism of dynamic ferrite transformation in steels is clarified.
► A massive ferrite transformation above Ae3 is thermodynamically impossible.
► Ferrite nucleus can grow to a size more than 1mm in 0.5 s by paraequilibrium.
► Paraequilibrium is the most possible mechanism for the dynamic transformation.