The Bainite in Low Carbon Low Alloy High Strength Steels

Ohmori, Yasuya; Ohtani, Hiroo; Kunitake, Tatsuro

doi:10.2355/tetsutohagane1955.57.10_1690

Cited by 25 publications

(28 citation statements)

References 4 publications

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“…In the upper part of the temperature range of bainite formation (above approximately 400°C for En 24), the transformation is very slow and incomplete, according to the experimental curves. In the literature, this phenomenon has been reported for many experimental data; [7,27,28] however, no conclusive explanation has been given as to the reason the transformation to bainite in the high temperature range is incomplete in such steels with a low Si and Al content. Based on its morphology, the bainite formed in this temperature range is sometimes called granular bainite.…”

Section: Resultsmentioning

confidence: 91%

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: Resultsmentioning

confidence: 91%

Modeling Start Curves of Bainite Formation

Bohemen

2009

Metall Mater Trans A

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“…In some areas, the interspaces transform with the cooperative mode of the eutectoid reaction. [2,4] In other cases, a plate splits up into several thinner plates, as for the plate indicated by the vertical arrow in Figure 11, and these plates can diverge to fill a wider space and in a section may look like a broom. Figure 12 is a higher magnification of the small packet close to the bottom of Figures 7 through 9.…”

Section: Observationsmentioning

confidence: 99%

“…IT is well known that bainitic ferrite formed in the upper temperature range is lath shaped; [1][2][3] i.e., the length is much larger than the width, which, in turn, is much larger than the thickness. One may, thus, talk about broad faces, short edges, and long edges, as illustrated in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Widening of Laths in Bainite

Yin

Hillert

Borgenstam

2017

Metall Mater Trans A

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Units of bainite in Fe-C alloys from the upper temperature range inherit their shape from Widmansta¨tten plates of ferrite, which are lathlike. The thickness increases by long-range diffusion of carbon and the length by short-range diffusion of carbon from the advancing edge of the tip. Both have been studied extensively and are fairly well understood. Widening growth seems to have been much neglected, but a study of some aspects of widening is now presented. The present report is the last one in a series of four morphological studies of bainite, isothermally formed in Fe-C alloys with 0.3 or 0.7 mass pct carbon, mainly in the upper temperature range. It contains a number of morphological observations made on cross sections of packets of bainite, and it elucidated a number of interesting questions about bainite and resulted in some proposals. The ferrite plates in a packet are nucleated as a group on a grain boundary, not each one separately on the side of a prior plate. Lengthening occurs by advancement of a short edge that is formed in close contact to the grain boundary. Widening of laths does not start spontaneously. It is initiated by a modification of the structure of the long edge of the lath. When it then moves, the lattice of the new ferrite is rotated relative to the ferrite formed by lengthening and the habit plane is different. In a section through the length direction, it is difficult to recognize what part of ferrite has formed by widening growth. Furthermore, it is proposed that the individual plates in a microstructure, previously used to illustrate subunits formed by repeated nucleation, were nucleated on a hidden grain boundary.

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“…The temperature range of this structure, therefore, is within that of proeutecoid ferrite formation and can be separated from the C-curve for bainite. 65,66) Thus in the present paper, this structure will be defined as "Widmanstätten ferrite" and will be separated from bainitic ferrite.…”

Section: Widmanstätten Ferrite and Bainite Transformationsmentioning

confidence: 99%

Advances in Physical Metallurgy and Processing of Steels. Microstructural Evolutions with Precipitation of Carbides in Steels.

Ohmori

2001

ISIJ International

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The studies on the crystallographic features of diffusional transformation of austenite in various steels have been reviewed. A primary ferrite forming at an austenite grain boundary is related to at least one of the austenite grains separated by the boundary with the Bain correspondence. In the case of the microstructures containing both ferrite and carbides such as pearlite, degenerate pearlite, interphase precipitation of alloy carbides, and upper and lower bainites, the crystallographic relationships between ferrite and carbides provide further information to elucidate the transformation mechanisms. In the present report, therefore, the orientation relationships between ferrite, carbide and austenite as well as the habit planes of platelike transformation products and the mechanisms of transformations are discussed.

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The Bainite in Low Carbon Low Alloy High Strength Steels

Cited by 25 publications

References 4 publications

Modeling Start Curves of Bainite Formation

Modeling Start Curves of Bainite Formation

Widening of Laths in Bainite

Advances in Physical Metallurgy and Processing of Steels. Microstructural Evolutions with Precipitation of Carbides in Steels.

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