Preparation of nanostructured bainite in medium-carbon alloysteel

Zhang, M.; Wang, T.S.; Wang, Y.H.; Yang, Jian; Zhang, F.C.

doi:10.1016/j.msea.2013.01.046

Cited by 34 publications

(17 citation statements)

References 16 publications

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“…While extensive work has been done on a single alloy containing 0.5 C wt. % [47,49,[60][61][62][63], only in the case of Refs. [56,64], the carbon content was lowered to 0.2 wt.…”

Section: Deformation Of Austenite (Ausforming)mentioning

confidence: 99%

“…Zhang et al [47] showed that ausforming decreased the Ms, thereby enabling isothermal transformation at lower temperatures, thus facilitating the formation of nanostructured bainite. Besides this, decreasing the ausforming temperature and increasing the This same technique has received attention as a means of accelerating the sluggish bainitic transformation of (low temperature) nanostructured bainite and hence, different deformation routes have been tested, not only revealing accelerated transformation kinetics but also achieving an extra refinement of the microstructure [47][48][49][50][51][52][53][54][55][56][57][58][59]. While extensive work has been done on a single alloy containing 0.5 C wt.…”

Section: Deformation Of Austenite (Ausforming)mentioning

confidence: 99%

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Transferring Nanoscale Bainite Concept to Lower C Contents: A Perspective

García‐Mateo

Paul

Somani

et al. 2017

Metals

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Abstract:The major strengthening mechanisms in bainitic steels arise from the bainitic ferrite plate thickness rather than the length, which primarily determines the mean free slip distance. Both the strength of the austenite from where the bainite grows and the driving force of the transformation, are the two factors controlling the final scale of the bainitic microstructure. Usually, those two parameters can be tailored by means of selection of chemical composition and transformation temperature. However, there is also the possibility of introducing plastic deformation on austenite and prior to the bainitic transformation as a way to enhance both the austenite strength and the driving force for the transformation; the latter by introducing a mechanical component to the free energy change. This process, known as ausforming, has awoken a great deal of interest and it is the object of ongoing research with two clear aims. First, an acceleration of the sluggish bainitic transformation observed typically in high C steels (0.7-1 wt. %) transformed at relatively low temperatures. Second, to extend the concept of nanostructured bainite from those of high C steels to much lower C contents, 0.4-0.5 wt. %, keeping a wider range of applications in view.Keywords: bainite; ausforming; kinetics; plate thickness Structural Refinement of Bainitic Steels: General ConsiderationsBainitic steels can be designed on the basis of the theory that predicts the highest temperature at which bainite (Bs) and martensite (Ms) can start to form in a steel of a given composition. These two temperatures constitute the upper and lower limits at which the isothermal heat treatment can be performed to generate bainite.It has been reported that bainitic ferrite plate thickness depends primarily on three parameters, i.e., (1) the strength of the austenite at the transformation temperature, (2) the dislocation density in the austenite and (3) the chemical free energy change accompanying transformation [1][2][3]. In accord, a strong austenite possessing a high dislocation density and a large driving force results in finer plates. Austenite strength and dislocation density refine the structure by increasing the resistance to interface motion, and the thermodynamic driving force refines the structure by increasing the nucleation rate. All three factors-austenite strength, dislocation density and driving force-increase

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“…While extensive work has been done on a single alloy containing 0.5 C wt. % [47,49,[60][61][62][63], only in the case of Refs. [56,64], the carbon content was lowered to 0.2 wt.…”

Section: Deformation Of Austenite (Ausforming)mentioning

confidence: 99%

Section: Deformation Of Austenite (Ausforming)mentioning

confidence: 99%

Transferring Nanoscale Bainite Concept to Lower C Contents: A Perspective

García‐Mateo

Paul

Somani

et al. 2017

Metals

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“…By comparing with that at 250°C, it is found that as the regeneration temperature increases, the strength of the weld decreases, while the elongation increases. For nanostructured bainite, with transformation temperature increasing, the fraction of retained austenite increases [28][29][30]. Therefore, an increasing regeneration temperature can also lead to an increase in the fraction of remaining austenite in the weld.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Microstructure and mechanical properties of nanostructured bainite weld with regeneration

et al. 2014

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Because of the brittle martensite crystalline structure, nanostructured bainitic steel is very difficult to be welded and easily form cracks in the welded joint, which limits the scope of their application. Regeneration treatment can lead to nanostructured bainite formation in the welded joints, preventing further degradation of the welded joint. Detailed changes of microstructures and mechanical properties of the weld are characterized here. Coarse inter-dendrite structures appear in the weld due to welding segregation, and are confirmed to be retained austenite by TEM. Moreover, an extraordinary combination of strength and ductility of the weld is achieved. The ultimate tensile strengths are 1913MPa and 2115MPa when regeneration temperatures are 250 °C and 230 °C. The corresponding elongations are 5.14% and 2.3%. In addition, the tension fracture behaviour and crack propagation mode of the weld are investigated.

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“…F. G. Caballero et al [3][4][5] developed a high-carbon high-silicon bainite steel through isothermal transformation at low temperatures, and a nanobainite steel (high toughness of 30 MPa m 1/2 and high strength of 2500 MPa) with microstructure of the nanoscale bainite plate (50 nm) and RA films can be prepared. M. Zhang et al [6] found that high hardness (592-628 HV) bainite can be obtained in supercooled austenite with medium carbon high-silicon composition during the deformation and following austempering at 250 • C.…”

Section: Introductionmentioning

confidence: 99%

“…The stability and strength of the parent-austenite can be enhanced by adding carbon, manganese or chromium, which in turn reduces the bainite start transformation temperature (Bs). These previous positive achievements have made it possible for bainite transformation at low temperature [6,7].…”

Section: Introductionmentioning

confidence: 99%