Influence of bainite reaction on the kinetics of carbon redistribution during the Quenching and Partitioning process

Nishikawa, Arthur Seiji; Santofimia, M.J.; Sietsma, Jilt; Goldenstein, Hélio

doi:10.1016/j.actamat.2017.09.048

Cited by 61 publications

(24 citation statements)

References 34 publications

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“…As the partitioning mechanism is fast, the Pt parameter has in practice little effect except if other physical mechanisms take place. The so-called partitioning process can in fact be hindered by a possible carbide free bainitic transformation in retained austenite [ 3 , 4 , 5 , 6 ], by carbon segregations on martensite defects [ 7 ], and also by carbide precipitation in martensite [ 6 , 8 , 9 , 10 , 11 ]. These two last processes also occur commonly when tempering as-quenched martensitic steels [ 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

In Situ Investigation of the Iron Carbide Precipitation Process in a Fe-C-Mn-Si Q&P Steel

et al. 2018

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Quenching and Partitioning (Q&P) steels are promising candidates for automotive applications because of their lightweight potential. Their properties depend on carbon enrichment in austenite which, in turn, is strongly influenced by carbide precipitation in martensite during quenching and partitioning treatment. In this paper, by coupling in situ High Energy X-Ray Diffraction (HEXRD) experiments and Transmission Electron Microscopy (TEM), we give some clarification regarding the precipitation process of iron carbides in martensite throughout the Q&P process. For the first time, precipitation kinetics was followed in real time. It was shown that precipitation starts during the reheating sequence for the steel studied. Surprisingly, the precipitated fraction remains stable all along the partitioning step at 400 °C. Furthermore, the analyses enable the conclusion that the iron carbides are most probably eta carbides. The presence of cementite was ruled out, while the presence of several epsilon carbides cannot be strictly excluded.

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Section: Introductionmentioning

confidence: 99%

In Situ Investigation of the Iron Carbide Precipitation Process in a Fe-C-Mn-Si Q&P Steel

et al. 2018

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“…Moreover, Nishikawa et al [32] demonstrated that the kinetics of carbon partitioning from martensite to austenite is controlled by carbon diffusion in martensite and little affected by the simultaneous occurrence of bainite reaction by simulation. Therefore, the CCET model assumes that carbon partitioning from martensite to austenite is completed before the austenite starts to decompose.…”

Section: Methodsmentioning

confidence: 99%

Modeling retained austenite in Q&P steels accounting for the bainitic transformation and correction of its mismatch on optimal conditions

Chen

Wang

et al. 2020

Acta Materialia

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Modeling retained austenite in quenching and partitioning (Q&P) steels remains a challenge, and the conventional 'constrained carbon equilibrium' (CCE) model fails to predict the optimal condition for achieving the maximal amount of retained austenite in various systems, which impedes the optimization of the Q&P process. One of the main limitations is that the possible decomposition of austenite to bainite during partitioning is completely ignored by the essential assumptions of the Q&P process and hence the associated CCE model. In this study, a CCET model that combines the conventional CCE model with the T0 model for the bainitic transformation and incorporates the effect of the isothermal bainitic transformation to describe the austenite stability during the Q&P process has been proposed. A detailed comparison between the experimental observation and model predictions demonstrated that the retained austenite could be better described by the CCET model, including its carbon content. The current model therefore provides a more accurate approach for tailoring the amount and stability of retained austenite after the Q&P processing of Fe-C-Mn-Si steels.

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“…In other words, this velocity is critical for the determination of the area of retained austenite around tempered martensite plates, especially for low-carbon steels, in order to design the structural and mechanical properties of the material, since three different phenomena could occur during the partitioning stage: (i) The amount of austenite's carbon enrichment to stabilize it after the final quench; (ii) Nucleation and growth of third phases (e.g., bainitic ferrite); and (iii) Carbide precipitation. Nishikawa et al [27] modeled the influence of the bainite reaction on the kinetics of carbon redistribution during the Q&P process. Simulations indicate that the kinetics of carbon partitioning from martensite to austenite is controlled by carbon diffusion in austenite and is affected only to a small extent by the decomposition of austenite into bainitic ferrite.…”

Section: Carbon Partitioningmentioning

confidence: 99%

Effect of Carbon Partitioning, Carbide Precipitation, and Grain Size on Brittle Fracture of Ultra-High-Strength, Low-Carbon Steel after Welding by a Quenching and Partitioning Process

Forouzan

Guitar

Vuorinen

et al. 2018

Metals

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To improve the weld zone properties of Advanced High Strength Steel (AHSS), quenching and partitioning (Q&P) has been used immediately after laser welding of a low-carbon steel. However, the mechanical properties can be affected for several reasons: (i) The carbon content and amount of retained austenite, bainite, and fresh martensite; (ii) Precipitate size and distribution; (iii) Grain size. In this work, carbon movements during the partitioning stage and prediction of Ti (C, N), and MoC precipitation at different partitioning temperatures have been simulated by using Thermocalc, Dictra, and TC-PRISMA. Verification and comparison of the experimental results were performed by optical microscopy, X-ray diffraction (XRD), Scanning Electron Microscop (SEM), and Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive Spectroscopy (EDS) and Electron Backscatter Scanning Diffraction (EBSD) analysis were used to investigate the effect of martensitic/bainitic packet size. Results show that the increase in the number density of small precipitates in the sample partitioned at 640 °C compensates for the increase in crystallographic packets size. The strength and ductility values are kept at a high level, but the impact toughness will decrease considerably.

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Influence of bainite reaction on the kinetics of carbon redistribution during the Quenching and Partitioning process

Cited by 61 publications

References 34 publications

In Situ Investigation of the Iron Carbide Precipitation Process in a Fe-C-Mn-Si Q&P Steel

In Situ Investigation of the Iron Carbide Precipitation Process in a Fe-C-Mn-Si Q&P Steel

Modeling retained austenite in Q&P steels accounting for the bainitic transformation and correction of its mismatch on optimal conditions

Effect of Carbon Partitioning, Carbide Precipitation, and Grain Size on Brittle Fracture of Ultra-High-Strength, Low-Carbon Steel after Welding by a Quenching and Partitioning Process

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