Effect of Retained Austenite on Formability of High Strength Sheet Steels.

Matsumura, Osamu; Sakuma, Yasuharu; Ishii, Yoshio; Zhao, Jiaqi

doi:10.2355/isijinternational.32.1110

Cited by 99 publications

(58 citation statements)

References 2 publications

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“…To calculate the stress (s) effect, the following equation is derived 28) .............. (6) where c 11 and c 12 are the elastic constants. e 2 is the strain tensor normal to the diffraction plane and is resulting from the change of interplanar spacing.…”

Section: Mechanical Stability Measured By Synchrotronmentioning

confidence: 99%

“…6,7,19) In the present work, the austenite fraction was determined under stress condition. To clarify the effect of orientation between the applied stress and the diffraction planes, the in situ XRD measurements are also performed using synchrotron radiation diffraction technique.…”

Section: Introductionmentioning

confidence: 99%

“…Detailed insight in the stability range of retained austenite is thus regarded to be of the highest importance for controlling the materials properties. Numerous modelings 3,4) and experiments [5][6][7][8][9] show that the factors influencing the stability of retained austenite in TRIP steels include the chemical composition in austenite, 6,7) size 4,5) and shape 9) of the grain and dislocation density, 8) etc. In the present study, the effect of carbon concentration in retained austenite is highlighted.…”

Section: Introductionmentioning

confidence: 99%

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Thermal and Mechanical Stability of Retained Austenite in Aluminum-containing Multiphase TRIP Steels.

et al. 2002

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Stability of retained austenite is the key issue to understand transformation-induced plasticity (TRIP) effect. In this work, both thermal stability and mechanical stability are investigated by thermo-magnetic as well as in situ conventional X-ray diffraction and micro synchrotron radiation diffraction measurements. The thermal stability in a 0.20C-1.52Mn-0.25Si-0.96Al (wt%) TRIP steel is studied in the temperature range between 5 and 300 K under a constant magnetic field of 5 T. It is found that almost all austenite transforms thermally to martensite upon cooling to 5 K and M S and M f temperatures are analyzed to be 355 and 115 K. Transformation kinetics on the fraction versus temperature relation are well described by a model based on thermodynamics. From the in situ conventional X-ray and synchrotron diffraction measurements in a 0.17C-1.46Mn-0.26Si-1.81Al (wt%) steel, the volume fraction of retained austenite is found to decrease as the strain increases according to Ludwigson and Berger relation. The diffraction measurements also show that the mechanical stability depends on the orientation of the grain with respect to the direction of the applied stress, and the austenite grains at an angle of 45°or 60°were found to be more stable than those at lower or higher angles. Both thermal and diffraction experiments show an increase in the average carbon concentration of the remaining austenite with lowering temperature or increasing stress. Thermal and mechanical stability of retained austenite is therefore attributed to the carbon distribution over different austenite grains.

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Section: Mechanical Stability Measured By Synchrotronmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermal and Mechanical Stability of Retained Austenite in Aluminum-containing Multiphase TRIP Steels.

et al. 2002

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“…Due to the absence of fine carbides, the steels have a high resistance to cleavage fracture and void formation. Then, there is the possibility of improving simultaneously the strength and toughness because of the ultrafine grain size (20-40 nm) of the bainitic ferrite plates and of further enhancing the ductility by a transformation induced plasticity effect (TRIP) 3) that increases the strain-hardening rate. It is well established that the strain induced transformation of austenite to martensite takes place between the M S temperature (martensite start temperature), and the M d temperature, above which the austenite becomes completely stable.…”

Section: Introductionmentioning

confidence: 99%

The Role of Retained Austenite on Tensile Properties of Steels with Bainitic Microstructures

García‐Mateo¹,

Caballero²

2005

Mater. Trans.

213

103

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In high-carbon, silicon-rich steels it is possible to obtain a very fine bainitic microstructure by transformation at low temperatures (200-300 C). This microstructure consists of slender ferrite plates, with thicknesses of several tens of nm, in a matrix of retained austenite. Whereas strength is mainly provided by to the fine scale of the ferrite plates (stronger phase), ductility is mostly controlled by the retained austenite (softer phase). Further improvement in ductility is achieved by strain induced transformation of austenite to martensite, the so called TRIP effect. In order to take full advantage of this effect, the mechanical stability of the austenite, i.e., its capability to transform to martensite under strain, must not be too low nor excessively high.Two main aspects of the mechanical stability of the retained austenite, morphology and chemical composition, have been studied to determine the role that these play on the ductility behaviour of the bainitic steels studied. It is suggested that the chemical composition has the strongest effect on the ductility of these new high strength alloys.

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“…They are evaluated to have excellent recyclability as well as high strength and ductility, 1,7) and thus are expected to be widely applied as structural materials for automobiles in the future.…”

mentioning

confidence: 99%

Effects of Tramp Elements on Formability of Low-carbon TRIP-aided Multiphase Cold-rolled Steel Sheets

Lee¹,

Kim²,

Lee³

et al. 2004

ISIJ International

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Effect of Retained Austenite on Formability of High Strength Sheet Steels.

Abstract: Effects of retained austenite on press formability were investigated, using austempered 0.4C-Si-1 .2Mn sheet steels with high tensile strength of more than 980 MPa.The

Cited by 99 publications

References 2 publications

Thermal and Mechanical Stability of Retained Austenite in Aluminum-containing Multiphase TRIP Steels.

Thermal and Mechanical Stability of Retained Austenite in Aluminum-containing Multiphase TRIP Steels.

The Role of Retained Austenite on Tensile Properties of Steels with Bainitic Microstructures

Effects of Tramp Elements on Formability of Low-carbon TRIP-aided Multiphase Cold-rolled Steel Sheets

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