Effect of Austempering Route on Microstructural Characterization of Nanobainitic Steel

Lan, Huifang; Du, Linxiu; Zhou, Na; Li, Xianghua

doi:10.1007/s40195-013-0006-2

Cited by 33 publications

(20 citation statements)

References 17 publications

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“…Tomita and co-workers attributed the increased strength properties to several factors, including martensite grain refining, due to partitioning of austenite by bainitic ferrite prior to martensite transformation, the predominant role of the major martensite plates, and strain-hardening of the bainitic ferrite, induced by the martensite transformation [18]. These explanations were also adopted by other researchers [13,[16][17][18]. However, the contribution of supersaturated carbon to hardening was excluded in this model.…”

Section: Introductionmentioning

confidence: 86%

“…When an austempering treatment is applied, wherein the austenised steel is firstly soaked for a short period in a salt bath of lower-bainite transformation and is subsequently quenched to room temperature, the resultant microstructure is a mixture of bainite, martensite and retained austenite [3,[12][13][14][15][16][17]. The new heat treatments were reported to bring about higher hardness and strength properties than the QT treatments, while the strengthening mechanisms have not been fully understood up to date.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

Luo

Kitchen

Abubakri

2017

Metals

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Ultrahigh strength steel 56NiCrMoV7 was austempered at 270 • C for different durations in order to investigate the microstructure evolution, carbon partitioning behaviour and hardness property. Detailed microstructure has been characterised using optical microscopy and field emission gun scanning electron microscopy. A newly developed X-ray diffraction method has been employed to dissolve the bainitic/martensitic ferrite phase as two sub-phases of different tetragonal ratios, which provides quantitative analyses of the carbon partitioning between the resultant ferrites and the retained austenite. The results show that, a short-term austempering treatment was in the incubation period of the bainite transformation, which resulted in maximum hardness being equivalent to the oil-quenching treatment. The associated microstructure comprises fine carbide-free martensitic and bainitic ferrites of supersaturated carbon contents as well as carbon-rich retained austenite. In particular, the short-term austempering treatment helped prevent the formation of lengthy martensitic laths as those being found in the microstructure of oil-quenched sample. When the austempering time was increased from 20 to 80 min, progressive decrease of the hardness was associated with the evolution of the microstructure, including progressive coarsening of bainitic ferrite, carbide precipitating inside high-carbon bainitic ferrite and its subsequent decarbonisation.

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Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

Luo

Kitchen

Abubakri

2017

Metals

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“…В процессе проведения остальных пяти режимов обработки, ко-гда Т изо ниже М н , могут образовываться следующие структурные со-ставляющие: атермический [11] и изотермический мартенсит, нижний бейнит [12][13][14], нижний бескарбидный бейнит, мартенсит охлаждения. Качественное и количественное разделение такого типа структурных составляющих -сложная задача, поэтому является темой отдельного исследования.…”

Section: результаты и их обсуждениеunclassified

Change the Microstructure of Sparingly Alloyed Steel Depending on the Speed of Continuous Cooling and Temperature of Isothermal Holding

Юрченко¹,

Панов²,

Simonov³

2017

PNIPU

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“…A novel quenching-partitioning-tempering (Q-P-T) treatment was applied to 0.2C-1.5Mn-1.5Si-0.6Cr-0.05Nb (wt%) steel, and it resulted in about 10 vol% retained austenite in the steel, compared to about nil percent retained austenite after the traditional quenching-tempering treatment, which can influence the stress-strain property considering the possible strain-induced austenite-martensite transformation [6]. Low-temperature nanobanitic structure was obtained for the steel with 0.85 wt% C, through two-step austempering, which gave a high tensile strength of 1955 MPa with a total elongation of 7% [7]. The effect of a relatively high isothermal temperature (400°C) on the microstructure of a low-carbon, high-Al low-Si steel was studied, and the bainite structure produced a high product of tensile strength and elongation as 17,685 MPa% [8].…”

Section: Introductionmentioning

confidence: 99%

Effect of Austempering–Partitioning on the Bainitic Transformation and Mechanical Properties of a High-Carbon Steel

Han

Chen

2015

Acta Metall. Sin. (Engl. Lett.)

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The 1.1C-1.5Si-1.1Mn-1.4Cr-0.5Mo-0.6Al-0.6Co (in wt%) steel was treated, respectively, by isothermal austempering process and newly developed austempering-partitioning-tempering process (A-P-T). After austempering at 250, 280 and 300°C for 38, 20 and 10 h, respectively, the sample microstructures were composed of bainitic ferrite plates and film-like retained austenite with thicknesses between 60 and 150 nm. The highest tensile strength of 2003 MPa and hardness value of 53.9 HRC were obtained for the steel after austempering at 250°C for 38 h, resulting from the combining effect of super-saturated martensite decarburization and stabilization of bainitic formation. After A-P-T treating (heated at 300°C for 8 h following water cooling, and then heated at 300°C for 2 h following air cooling), bamboo leaf-like martensite, primary and secondary bainites and retained austenite were observed. The thickness of the secondary bainitic ferrite plates formed during partitioning is much smaller than that of the primary bainite formed during 300°C austempering. Samples subjected to A-P-T treatment showed improvement in ductility compared to that subjected to austempering.

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Effect of Austempering Route on Microstructural Characterization of Nanobainitic Steel

Cited by 33 publications

References 17 publications

Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

Change the Microstructure of Sparingly Alloyed Steel Depending on the Speed of Continuous Cooling and Temperature of Isothermal Holding

Effect of Austempering–Partitioning on the Bainitic Transformation and Mechanical Properties of a High-Carbon Steel

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