Dislocation Substructures in Hot-deformed Ni-based Alloys: Simulation for Structure Evolution of Hot-worked Austenite in Low Carbon Steels

Adachi, Yoshitaka; Tomida, Toshiro; Hinotani, Shigeharu

doi:10.2355/isijinternational.40.suppl_s194

Cited by 25 publications

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“…Almost homogeneous distribution of equiaxed and cellar arrays of dislocations are observed, which are very similar to those observed in cold-rolled fcc alloys 33) as well as hot-rolled Ni30%Fe. 34,35) The average cell diameter is approximately 0.4 mm. Although the misorientation angle between neighboring cells is mostly very small, some of the cell walls in the present experiment show large misorientation over 10°a s shown in Fig.…”

Section: Ni-30%fe Model Alloymentioning

confidence: 99%

Grain Refinement of C–Mn Steel to 1 μm by Rapid Cooling and Short Interval Multi-pass Hot Rolling in Stable Austenite Region

et al. 2008

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Section: Ni-30%fe Model Alloymentioning

confidence: 99%

Grain Refinement of C–Mn Steel to 1 μm by Rapid Cooling and Short Interval Multi-pass Hot Rolling in Stable Austenite Region

et al. 2008

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“…Entwisle 22) and Magee 23) reported that kinetics of isothermally formed martensite depends largely on the grain size when it is down to 20 mm, and Wang et al 14) thought that nucleus density required by an athermal nucleation mechanism could be achieved only when the dispersed austenite grain size is as small as 1 mm. Adachi et al 18) even presented experimental evidence that the sizes of dislocation cells produced by austenitic deformation above 800°C were around 1 mm. The prior austenite grain size ranges from 15 to 28 mm in our investigation, thus, it could be estimated that this critical size is at least less than 10 mm, most likely in the scale of a few micrometers or even smaller, since the prior austenite grain sizes of industrial TRIP steels are usually quite fine.…”

Section: Mechanism For Influence Of Intercritical Deformation On Bainmentioning

confidence: 99%

“…The ferrite nucleated to form parallel and closely spaced arrays within one prior austenite grain. By using the similar model alloy, Adatchi et al 18) made the more detailed observation that deformation substructure are microbands below 700°C whilst equiaxed dislocation cell structures above 800°C. All of these previous researches support that austenitic deformation may produce such deformation microstructures as microbands and dislocation cells.…”

Section: Mechanism For Influence Of Intercritical Deformation On Bainmentioning

confidence: 99%

Effect of Intercritical Deformation on Bainite Formation in Al-containing TRIP Steel

Luo¹,

Zhao²,

Kruijver³

et al. 2003

ISIJ International

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The Influence of intercritical deformation, cooling rate and prior austenite grain size on bainite formation were investigated by dilatometry tests. Intercritical deformation (0-40 %) performed in steels with a prior austenite grain size of 15-28 mm leads to formation of more ferrite during the cooling and less bainite during the subsequent isothermal stage, and even almost no bainite is formed after 40 % strain. Fast cooling after deformation can suppress ferrite transformation. Relaxation following deformation can significantly, but not completely, reduce such effect of deformation due to the occurrence of recovery and recrystallization, particularly for the finer prior austenite grain size. When the prior austenite grain size was changed from 26.8 to 16.8 mm, bainite formation was suppressed. The mechanism for influence of deformation on bainite formation was discussed on the basis that deformation could refine the austenitic microstructure. Further, it is suggested that there is a critical size of austenite grains or subunits after deformation for the formation of bainite.KEY WORDS: TRIP steels; bainite formation; intercritical deformation; austenite grain size; cooling rate; relaxation.by relaxation for either 0 or 60 s; next, cooled to the bainitic stage (400°C) at 20 or 50°C/s and held for 10 min. Finally, they were quenched to room temperature by helium gas.The quenched samples were cut through cross-sections in the middle of deformed samples, and polished as normal, then etched with 5 % nital and rinsed with water followed by etching in a 10 % sodium metabisulphite solution. This etching is intended to better distinguish between upper bainite and ferrite for quantification of phase fractions because both of them will appear as a light color under the optical microscope after nital etching. Contrastively, such etching can reveal ferrite as light gray, bainite/martensite as black and retained austenite (if preserved) as white. 6,7) In addition, nital and saturated picric acid were also used to reveal the prior austenite grain boundaries and ferrite subgrain boundaries. Image analysis software of Leica was used to quantify the volume fractions of ferrite in the quenched specimens and austenite grain sizes achieved from the solution at 950 and 1 100°C. There are three points in the process at which austenite fractions is determined to follow transformations taking place during the whole process, as shown in Fig. 1. Intercritical austenite fraction before the deformation, i.e. f v 1 g , is derived from the optical measurement of the ferrite fractions of interruptedly quenched samples. Similarly, the austenite fraction before bainite formation, i.e. f v 2 g in Fig.1, is also calculated from the measurements on the ferrite fractions of samples after the whole processing. The remained austenite fraction just after bainite formation, i.e. f v 3 g , is calculated from the dilation signals which will be discussed later. X-ray diffractometry is used to measure the quantity of retained austenite in some quenched spe...

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“…[3][4][5] Also we simulated the effect of the gradual variation in orientation within an austenite grain, which developed during the process of deformation, on the orientation distribution characteristics of statically transformed ferrite, and compared the results of this simulation with the experimental observations. In this simulation, the K-S relationship between the deformed austenite and statically transformed ferrite was assumed.…”

Section: Introductionmentioning

confidence: 99%

“…9) Using this concept, the deformed grain structure of austenite has frequently been evaluated using Ni-30Fe alloy. [3][4][5] This alloy is known to have a stacking fault energy similar to that of low carbon austenite at high temperature.…”

mentioning

confidence: 99%

The Orientation Distribution of Ferrite Grains Dynamically and Statically Transformed from Heavily Deformed Austenite

Kang

Lee

2004

Mater. Trans.

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The orientation distribution of ferrite grains formed by dynamic and static transformation was examined using the electron backscattered diffraction technique. The orientation of ferrite grains, transformed both dynamically and statically from deformed austenite, showed a large deviation from the Kurdjumov-Sachs (K-S) orientation relationship. The deformed austenite grain structure modeled using Ni-30Fe alloy showed inhomogeneous and localized deformations within the austenite grains. A large orientation variation was observed across this localized deformation zone, and the large deviation of the ferrite orientation from the K-S relationship was attributed to the nucleation of ferrite from this localized deformation region.

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Dislocation Substructures in Hot-deformed Ni-based Alloys: Simulation for Structure Evolution of Hot-worked Austenite in Low Carbon Steels

Abstract: The dislocation substructure in compressively deformed fcc 70Ni-30Fe and 67Ni-30Fe-3Ti alloys was investigated to understand or model microstructural evolution in austenite of low carbon steels during hot deformation. These Ni-

Cited by 25 publications

References 0 publications

Grain Refinement of C–Mn Steel to 1 μm by Rapid Cooling and Short Interval Multi-pass Hot Rolling in Stable Austenite Region

Grain Refinement of C–Mn Steel to 1 μm by Rapid Cooling and Short Interval Multi-pass Hot Rolling in Stable Austenite Region

Effect of Intercritical Deformation on Bainite Formation in Al-containing TRIP Steel

The Orientation Distribution of Ferrite Grains Dynamically and Statically Transformed from Heavily Deformed Austenite

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