Pearlite in Multicomponent Steels: Phenomenological Steady-State Modeling

Yan, Jia-Yi; Ågren, John; Jeppsson, Johan

doi:10.1007/s11661-020-05679-3

Cited by 10 publications

(5 citation statements)

References 52 publications

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“…22) Similarly, the phenomenon also applied under δ -pearlite growth, as the slope of experiment v and S shows n < − 2 and gradually deviate at long-time carburization specimens. Of course, although the solute drag effect as well as the interfacial mobility depleting the driving force should be also considered, 23) composition change is the principal reason why the calculated v B is larger than the experimental v. From these results, it is possible to control the unidirectional lamellar structure of δ -pearlite.…”

Section: Growth Kinetics Of δ -Pearlitementioning

confidence: 97%

<i>δ</i>–pearlite Reaction by Carburization in Fe–Cr Binary Alloy

Nakada

2022

ISIJ Int.

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The eutectoid transformation of δ -ferrite → γ -austenite + carbide by carburization was studied comprehensively with Fe-Cr binary alloy. It was observed that δ -pearlite consisted of γ -austenite and M 23 C 6 carbide formed with unidirectional lamellar structure parallel to the carburization direction, and consequently the γ -austenite transformed to α'-martensite on quenching. The reconstruction of the parent γ -austenite orientation revealed that the both of austenite and M 23 C 6 phases have a preference growth along [011] direction while keeping a cube-on-cube orientation relationship within δ -pearlite. The growth rate of δ -pearlite followed parabolic kinetics, and thus, the interlamellar spacing of δ -pearlite was gradually increased according to the Zener-Hillert model. Furthermore, the δ -pearlite formation mechanism was discussed under PE (para-equilibrium), NPLE (non-partitioning local equilibrium), and PLE (partitioning local equilibrium) conditions. As a result, it was concluded that the PLE model with long-range Cr diffusion through the interface diffusion is dominant, which leads to the redistribution of Cr between austenite and M 23 C 6 at the eutectoid reaction front.

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Section: Growth Kinetics Of δ -Pearlitementioning

confidence: 97%

<i>δ</i>–pearlite Reaction by Carburization in Fe–Cr Binary Alloy

Nakada

2022

ISIJ Int.

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“…where x is the mole fraction of carbon in the alloy, R is the universal gas constant in J mol −1 K −1 , and T is the temperature in K. Equation (19) can then be rearranged to give an expression for the time required to precipitate cementite, t θ . Takahashi and Bhadeshia concluded that 0.01 was a reasonable value for ξ(t), as this gave a "detectable" volume fraction of cementite.…”

Section: Predicting Cementite Formation Kineticsmentioning

confidence: 99%

“…This then questions whether predictions can be accurately extrapolated past these systems to alloys with more than three components. Some of the more recent of these models [19,21] predicted the behaviour of quaternary alloys reasonably well; however, the accuracy of these predictions showed a notable decrease. Thermo-Calc predictions are also very slow, when compared to the rapidness of empirical and semi-empirical models, making the software undesirable when a large number of CCT predictions are required.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the majority of these packages are not open source, thereby limiting their accessibility. The CCT predictions made by Thermo-Calc are built on computational thermodynamics and diffusion kinetics by adopting models developed by Lange et al [18] for ferrite, Yan et al [19] for pearlite, Leach et al [20] and Leach et al [21] for bainite and Widmanstätten ferrite, and Stormvinter et al [22], Hanumantharaju [23] and Huyan et al [24] for martensite. Most of these models were calibrated using either binary or binary and ternary alloys.…”

Section: Introductionmentioning

confidence: 99%

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A Rapid, Open-Source CCT Predictor for Low-Alloy Steels, and Its Application to Compositionally Heterogeneous Material

Collins

Piemonte

Taylor

et al. 2023

Metals

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The ability to predict transformation behaviour during steel processing, such as primary heat treatments or welding, is extremely beneficial for tailoring microstructures and properties to a desired application. In this work, a model for predicting the continuous cooling transformation (CCT) behaviour of low-alloy steels is developed, using semi-empirical expressions for isothermal transformation behaviour. Coupling these expressions with Scheil’s additivity rule for converting isothermal to non-isothermal behaviour, continuous cooling behaviour can be predicted. The proposed model adds novel modifications to the Li model in order to improve CCT predictions through the addition of a carbon-partitioning model, thermodynamic boundary conditions, and a Koistinen–Marburger expression for martensitic behaviour. These modifications expanded predictions to include characteristic CCT behaviour, such as transformation suppression, and an estimation of the final constituent fractions. The proposed model has been shown to improve CCT predictions for EN3B, EN8, and SA-540 B24 steels by better reflecting experimental measurements. The proposed model was also adapted into a more complex simulation that considers the chemical heterogeneity of the examined SA-540 material, showing a further improvement to CCT predictions and demonstrating the versatility of the model. The model is rapid and open source.

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“…Our previous research showed that increasing the heating rate of Fe-C-Cr bearing steel with an initial microstructure of lamellar pearlite also abnormally improved the austenitization rate [ 17 ]. For the lamellar pearlite, the lamellar spacing and the interfacial diffusion of the solutes should influence the pearlite to austenite transformation rate [ 18 ]. As the lamellae of pearlite have certain orientations, the relationship between the austenite growth direction and lamellar orientation also influences the transformation rate.…”

Section: Introductionmentioning

confidence: 99%

Prediction of the Non-Isothermal Austenitization Kinetics of Fe-C-Cr Low Alloy Steels with Lamellar Pearlite Microstructure

Zhang

et al. 2022

Materials

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The austenitization of low alloy steels during rapid heating processes was involved in many kinds of advanced heat treatment technologies. Most of the previous research on the austenitization kinetics was focused on the spherical pearlite microstructures, which were different from the lamellar pearlite microstructures. In the present research, to predict the non-isothermal austenitization process of an Fe-C-Cr steel with lamellar pearlite, a novel 3-dimensional (3D) cellular automata model, which considered the influences of the coupling diffusion of Cr and C, and the interfacial diffusion between pearlite lamellae and the pearlite lamellar orientation, was established based on the thermodynamic equilibrium data obtained from the Thermo-Calc software and the simulation results of the DICTRA module. To clarify the influences of the heating rate on the austenitization kinetics and validate the simulation results, the austenitization processes of a Fe-1C-1.41Cr steel for different heating rates were studied with a series of dilatometric experiments. The good agreements between the cellular automata simulation results and the experimental results showed that the newly proposed cellular automata model is reasonable. The experimental results show an obvious change of the transition activity energies from the low to high heating rates. The transition from partitioning local equilibrium (PLE) to non-partitioning local equilibrium (NPLE) mechanisms was proved with DICTRA simulations. Basing on the simulation results, the influences of the pearlite lamellae orientation on the austenitization kinetics and the topological aspects of austenite grains were evaluated. In addition, the topological aspects of the rapidly austenitized grains were also compared to the normal grains.

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Pearlite in Multicomponent Steels: Phenomenological Steady-State Modeling

Cited by 10 publications

References 52 publications

<i>δ</i>–pearlite Reaction by Carburization in Fe–Cr Binary Alloy

<i>δ</i>–pearlite Reaction by Carburization in Fe–Cr Binary Alloy

A Rapid, Open-Source CCT Predictor for Low-Alloy Steels, and Its Application to Compositionally Heterogeneous Material

Prediction of the Non-Isothermal Austenitization Kinetics of Fe-C-Cr Low Alloy Steels with Lamellar Pearlite Microstructure

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