Kinetic Transitions during Non-Partitioned Ferrite Growth in Fe-C-Mn Alloys

Abstract

Ferrite growth behavior in Fe-C-Mn alloys has been studied using controlled decarburization experiments. Two types of kinetic transition are considered. A first transition is proposed which involves a change from ParaEquibrium (PE) contact conditions at short times to Local-Equilibrium with Negligible Partitioning at longer times (LENP). This transition is attributed to the gradual build up of an alloying element spike due to the diffusion of Mn across the interface. The cross-interface mobility of Mn is estimated based on the experimental results. In some alloys, we observe a transition to extended PE states at high temperatures. A simple model which quantitatively describes the experimental observations over a range of composition and temperature is proposed. A key feature of this model is the introduction of an alloying element capacity of the moving ferrite/austenite interface, X*. The introduction of this quantity is purely guided by the experimental data and, at present, there is no physically based method for calculating it.

Evolution of cementite composition along the processing of cold-rolled and annealed Dual-Phase steels

“…Pandit [26,47] are rationalized in order to predict thermodynamically the composition of the pearlite's constituents and thus explain the measured compositions inside cementite in the as-transformed state (Sample 1). To our knowledge, we are the first to bring experimental evidence of the validity of such a thermodynamical prediction for hypoeutectoid steels in anisothermal condition.…”

Solute drag modeling for ferrite growth kinetics during precipitation experiments

“…∆E is half the dierence between the solute chemical potentials in austenite µ γ X and in ferrite µ α X . The binding energy parameter has been used to express the segregation behavior of the substitutional element at the interface [12,14,15,45,46,47]. However, this parameter as calculated with this approach 6 depends on the conditions under which the calculations are made.…”

Multiscale Modeling of Phase Transformations in Steels

“…As a first step of this validation, systematic laboratory experiments were conducted using Fe model alloys where ferrite growth was monitored using the method of controlled decarburization. 34,35 These experiments consist of reheating the specimen into the austenite single-phase region in an atmosphere of wet hydrogen. The oxygen potential of this atmosphere is high enough to remove carbon from the specimen but too low to oxidize iron.…”