Enhancing technological prospect of nanostructured bainitic steels by the control of thermal stability of austenite

Królicka, Aleksandra; Żak, Andrzej; Caballero, Francisca G.

doi:10.1016/j.matdes.2021.110143

Cited by 18 publications

(9 citation statements)

References 162 publications

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“…However, this requires further research and consideration in the future, especially in terms of industrial conditions. Also, another prospect is the development of new grades of bainitic steel for continuous cooling processes with enhanced thermal stability [30].…”

Section: Resultsmentioning

confidence: 99%

Decomposition mechanisms of continuously cooled bainitic rail in the critical heat-affected zone of a flash-butt welded joints

Królicka

Żak

Kuziak

et al. 2021

Materials Science-Poland

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The joining process of bainitic rails is significant in terms of their industrialization in high-speed and heavy-loaded railways. This paper demonstrates the microstructure changes in the critical zone of the welded joint, which is responsible for the greatest deterioration in mechanical properties. Extensive progress in the decomposition of the retained austenite and bainitic ferrite occurs in the low-temperature heat-affected zone (LTHAZ) of the flash-butt welded joint of low-carbon bainitic rail. The decomposition products of the retained austenite were mainly a mixture of cementite and ferrite. The cementite was mainly precipitated at the boundary of the bainitic ferrite laths, which indicates lower thermal stability of the filmy austenite. Moreover, it was found that a part of the refined blocky retained austenite was decomposed into the ferrite and nanometric cementite, while another remained in the structure. The decomposition mechanisms are rather heterogeneous with varying degrees of decomposition. A relatively high proportion of dislocations and stress fields prove the occurrence of residual stresses formed during the welding process.

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Section: Resultsmentioning

confidence: 99%

Decomposition mechanisms of continuously cooled bainitic rail in the critical heat-affected zone of a flash-butt welded joints

Królicka

Żak

Kuziak

et al. 2021

Materials Science-Poland

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“…On the other hand, it should also be mentioned that the EBSD technique used did not reveal the presence of austenite with film-like morphology due to its nanoscale dimensions, which is characterized by higher stability and carbon concertation compared to blocky morphology. [65] On the other hand, the XRD profile did not reveal any significant content of austenite in the fracture area, thus it may be concluded that it underwent a martensitic transformation.…”

Section: The Microstructure Evolution Prior the Crack Tipmentioning

confidence: 91%

The Role of Microstructure Morphology on Fracture Mechanisms of Continuously Cooled Bainitic Steel Designed for Rails Application

Królicka

Lesiuk

Kuziak

et al. 2022

Metall Mater Trans A

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The low-carbon bainitic steel after a continuous cooling process was subjected to fracture toughness investigations using the J-integral approach. The research was focused on the determination of microstructural factors influencing the fracture processes considering the crystallographic units, as well as dimensions and morphology of phases. It was found that the fracture surface is characterized by complex fracture mechanisms (quasi-cleavage, transcrystalline cleavage–ductile, and ductile mode). It was found that the main features influencing the cracking processes are bainitic ferrite packets and prior austenite grain boundaries. The changes in the crack path were also related to the changes in the misorientation angles, and it was found that changes in the crack path direction occur mainly for the bainitic ferrite packets (HABs). Also, the fracture process zone induced by the crack tip was identified. At a distance of about 4 to 5 µm from the fracture, the retained blocky austenite transformed into martensite was observed. Due to the high carbon content in the retained austenite, the transformed martensite was brittle and was the site of microcracks nucleation. Another origin of microcracks nucleation were M/A constituents occurred in the initial microstructure. In the crack tip area, the reduced dislocation density in the bainitic ferrite, which was caused by the formation of sub-grains, was also determined. Finally, the prospective improvement of the fracture toughness of bainitic steels was determined.

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“…Such a behavior requires research for improvement. Softening is a phenomenon linked to the direct decomposition of austenite, into a mixture of ferrite and cementite during tempering [81,82] at temperatures above 550 • C for these compositions [72]. The blocky morphology of the retained austenite is most favorable than film-like austenite against this phenomenon due to its lower carbon concentration [81].…”

Section: Low/medium C Content Cfb Steels: Transformation On Continuou...mentioning

confidence: 99%

“…Softening is a phenomenon linked to the direct decomposition of austenite, into a mixture of ferrite and cementite during tempering [81,82] at temperatures above 550 • C for these compositions [72]. The blocky morphology of the retained austenite is most favorable than film-like austenite against this phenomenon due to its lower carbon concentration [81]. The addition of a 0.2 wt.% of V has been reported to suppress it, but its influence on a probable "indirect" decomposition of austenite, i.e., its destabilization leading to fresh martensite upon cooling, remains unclear [72].…”

Section: Low/medium C Content Cfb Steels: Transformation On Continuou...mentioning

confidence: 99%

Viewpoints on Technological Aspects of Advanced High-Strength Bainitic Steels

Morales-Rivas

2022

Metals

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The development of advanced high-strength bainitic steels has been preceded and linked to different metallurgical advances, both in the field of fundamental materials science and in technological fields closer to the production and final application. The diversity and abundance of documents in literature has favored the co-existence of extensive terminology in the context of advanced high-strength steels and bainitic steels. In this work, the concept of advanced high-strength bainitic steels is briefly revisited from a wide perspective, with the aim of highlighting the main limitations and challenges for further development of these microstructures.

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Enhancing technological prospect of nanostructured bainitic steels by the control of thermal stability of austenite

Cited by 18 publications

References 162 publications

Decomposition mechanisms of continuously cooled bainitic rail in the critical heat-affected zone of a flash-butt welded joints

Decomposition mechanisms of continuously cooled bainitic rail in the critical heat-affected zone of a flash-butt welded joints

The Role of Microstructure Morphology on Fracture Mechanisms of Continuously Cooled Bainitic Steel Designed for Rails Application

Viewpoints on Technological Aspects of Advanced High-Strength Bainitic Steels

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