New experimental evidence on the incomplete transformation phenomenon in steel

Caballero, Francisca G.; García‐Mateo, C.; Santofimia, M.J.; Miller, M.K.; Andrés, Carlos García de

doi:10.1016/j.actamat.2008.08.041

Cited by 146 publications

(73 citation statements)

References 29 publications

(29 reference statements)

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“…[9], which describes the relationship between K 1 C and B, is combined with Eq. [11], it follows that K 1 C = (170 kJ mol À1 À Q b )/(705 K), which is indicated by the solid line in Figure 8(b). The values of K 1 C can be evaluated from the B values listed in Table II using Eq.…”

Section: A Correlation Between B and Q Bmentioning

confidence: 91%

“…Calculations with Eq. [11] using N = 3 and 11 are indicated by the dashed lines in Figure 8(a), and it is seen that all data are within this range.…”

Section: A Correlation Between B and Q Bmentioning

confidence: 93%

“…The controversy between the two transformation mechanisms is an ongoing debate in literature. [8][9][10][11] Although diffusional models implicitly predict C-curve kinetics of bainite in accordance with experimental observations, many model parameters have to be chosen in the calculations, including an arbitrary incubation time. [12] On the other hand, kinetic simulations based on Bhadeshia's displacive transformation model predict a bainite start curve with a flat top.…”

Section: Introductionmentioning

confidence: 99%

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Modeling Start Curves of Bainite Formation

Bohemen

2009

Metall Mater Trans A

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It is demonstrated that calculations with a physically based model give an accurate description of the start curve of bainite formation in a wide range of steels. The temperature dependence of the overall kinetics, which determines the characteristic C shape of the start curve, is controlled by both the undercooling below the start temperature (T h À T) and an effective activation energy Q b . A systematic analysis of the model parameters extracted from the best fits of published time-temperature-transformation (TTT) data reveals a material-independent relationship, which means that the activation energy is in accordance with known details of the dislocationbased nucleation model of bainite. It is shown that the C shape of the start curve can be determined for a given alloying content using an empirical relationship derived for Q b and, in combination with the material-independent relationship, the kinetics of bainite can be predicted at all temperature levels.

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Section: A Correlation Between B and Q Bmentioning

confidence: 91%

“…Calculations with Eq. [11] using N = 3 and 11 are indicated by the dashed lines in Figure 8(a), and it is seen that all data are within this range.…”

Section: A Correlation Between B and Q Bmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Modeling Start Curves of Bainite Formation

Bohemen

2009

Metall Mater Trans A

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“…APT was successfully used to study solute redistribution in these steels. [8,9,18,26] However, to achieve this microstructure, heat treatment for 24 to 48 hours or longer is required, which makes these steels economically unviable for many applications outside the heavy section products. In addition, high C content poses a significant problem for welding of this steel.…”

mentioning

confidence: 99%

Understanding the Behavior of Advanced High-Strength Steels Using Atom Probe Tomography

Pereloma

Beladi

Zhang

et al. 2011

Metall Mater Trans A

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The key evidence for understanding the mechanical behavior of advanced high strength steels was provided by atom probe tomography (APT). Chemical overstabilization of retained austenite (RA) leading to the limited transformation-induced plasticity (TRIP) effect was deemed to be the main factor responsible for the low ductility of nanostructured bainitic steel. Appearance of the yield point on the stress-strain curve of prestrained and bake-hardened transformationinduced plasticity steel is due to the unlocking from weak carbon atmospheres of newly formed during prestraining dislocations.

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“…Thus, it can be assumed that after completion of bainitic transformation the amount of residual austenite should be very low. However, due to incomplete reaction phenomena a part of austenite usually remains untransformed in the microstructure [17].…”

Section: Resultsmentioning

confidence: 99%

The Comparative Study of the Microstructure and Phase Composition of Nanoausferritic Ductile Iron Alloy Using SEM, TEM, Magnetometer, and X-Ray Diffraction Methods

et al. 2017

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In this paper the microstructure and phase composition of ausferritic ductile iron alloy were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction methods. In order to obtain the nanoausferritic microstructure in the alloy, the austempering heat treatment was performed at relatively low temperature. As a result, a specific kind of microstructure, containing nanocrystalline ausferrite and retained austenite blocks, was obtained in each heat-treated sample. The volume fractions of phases were determined using different methods: MicroMeter software for scanning electron micrographs, stereological analysis for transmission electron micrographs, quantitative analysis of the X-ray diffraction spectra and magnetometer measurements. All methods revealed a high amount of retained austenite which varied as a function of the austempering treatment parameters. It was shown that the quantitative phase composition measured by X-ray diffraction and magnetometer, in all samples investigated, differs significantly from the stereological measurements and image analysis performed through the MicroMeter software. The possible reasons of the observed differences were discussed.

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New experimental evidence on the incomplete transformation phenomenon in steel

Cited by 146 publications

References 29 publications

Modeling Start Curves of Bainite Formation

Modeling Start Curves of Bainite Formation

Understanding the Behavior of Advanced High-Strength Steels Using Atom Probe Tomography

The Comparative Study of the Microstructure and Phase Composition of Nanoausferritic Ductile Iron Alloy Using SEM, TEM, Magnetometer, and X-Ray Diffraction Methods

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