Effect of retained austenite on impact toughness and fracture behavior of medium carbon submicron-structured bainitic steel

Zhou, Songbo; Hu, Feng; Zhou, Wenda; Cheng, Lin; Hu, Chengyang; Wu, Kaiming

doi:10.1016/j.jmrt.2021.07.011

Cited by 57 publications

(22 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…These excellent properties are attributed to the reasonable ratio of BF to RA [ 14 ]. The ultra-high strength comes from a submicron-sized BF lath and the solid solution strengthening of alloy elements; the toughness depends on the stability of RA [ 15 ]. There was a substantial amount of martensite in the one-step bainitic transformation process where the hard-brittle martensite did not effectively absorb energy and passivate cracks and had no obvious effect on the impact toughness of the steel.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Nanomechanics of Retained Austenite in Medium-Carbon Low-Temperature Bainitic Steel: A Critical Analysis of a One-Step versus a Two-Step Treatment

Zhou

Wang

et al. 2022

Materials

Self Cite

View full text Add to dashboard Cite

A two-step bainitic treatment with a final isothermal temperature below MS was adopted to obtain bainitic steel with abundant retained austenite (RA). Nanoindentation testing was used to investigate the stability of RA in bainite steel and clarify the effect of RA on the deformation of medium-carbon steel. The results showed that, in contrast to the traditional one-step approach, a greater amount of nanoscale RA film was obtained using the two-step treatment. This was due to a lower final bainitic transformation temperature, which induced a higher carbon concentration in the untransformed austenite in the stasis stage; this resulted in untransformed austenite with a higher carbon content existing as RA rather than forming martensite in the subsequent cooling process. In addition, it was determined that the increased stability of RA during the two-step transformation delayed the pop-in point.

show abstract

Section: Discussionmentioning

confidence: 99%

“…The 2θ scanning angles varied from 40° to 110° with a stepping angle of 0.033°. Finally, the volume fraction of RA was calculated by measuring the integrated intensities of the (111), (200), (220), and (311) austenite peaks and comparing them with the (110), (200), (211), and (202) martensite peaks [ 15 ].…”

Section: Methodsmentioning

confidence: 99%

Nanomechanics of Retained Austenite in Medium-Carbon Low-Temperature Bainitic Steel: A Critical Analysis of a One-Step versus a Two-Step Treatment

Zhou

Wang

et al. 2022

Materials

Self Cite

View full text Add to dashboard Cite

show abstract

“…After oil quenching, a large residual stress will be generated, which makes the steel easily produce cracks. After being subjected to a small impact, the unstable retained austenite will transform into untempered fresh martensite [22,23]. The fresh martensite makes the crack expand rapidly and greatly reduces the plasticity and toughness.…”

Section: Mechanical Performance Analysismentioning

confidence: 99%

Effect of Austempering on Mechanical Properties of Nb/V Microalloyed Bainitic Bearing Steel

et al. 2022

View full text Add to dashboard Cite

In this study, a multi-element microalloyed GCr15Si1MoNbV bainitic bearing steel was designed by adding trace amounts of Nb and V. The bainite/martensite/retained austenite/undissolved carbide multiphase bearing steel with a short heat-treated cycle and remarkable comprehensive mechanical properties was prepared via low-temperature austempering, which was compared with a traditional quenched and tempered martensitic microstructure. The results showed that the comprehensive mechanical properties of the low-temperature bainitic microstructure of the Nb/V microalloyed bearing steel were better than those of a traditional tempered martensitic microstructure. In addition, as the isothermal temperature increased, the impact toughness of experimental steel was significantly improved, and the hardness decreased slightly. The tensile strength was improved with the increase in isothermal time. As the isothermal temperature increased, the bainite content of the experimental steel rose, and the stability of the retained austenite enhanced due to more carbon atoms being partitioned into it. The research work in this paper made a preliminary exploration for the application of Nb/V microalloyed bainitic bearing steel in the bearing field and provided some basic data for reference.

show abstract

“…[23] In many investigations, it was stated that M/A constituents are the favorable site for crack nucleation and damage initiation. [13,24] Also, coarse retained blocky austenite during fracture transforms to martensite, preferentially in areas of low-carbon concentrations. [24] Another structural feature that may be connected to the crack nucleation process is the occurrence of coarse carbide or carbides colonies.…”

Section: Introductionmentioning

confidence: 99%

“…[13,24] Also, coarse retained blocky austenite during fracture transforms to martensite, preferentially in areas of low-carbon concentrations. [24] Another structural feature that may be connected to the crack nucleation process is the occurrence of coarse carbide or carbides colonies. [25] On the other hand, filmy austenite is a feature that positively influences the fracture process and hinders crack propagation.…”

Section: Introductionmentioning

confidence: 99%

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

View full text Add to dashboard Cite

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.

show abstract

Effect of retained austenite on impact toughness and fracture behavior of medium carbon submicron-structured bainitic steel

Cited by 57 publications

References 44 publications

Nanomechanics of Retained Austenite in Medium-Carbon Low-Temperature Bainitic Steel: A Critical Analysis of a One-Step versus a Two-Step Treatment

Nanomechanics of Retained Austenite in Medium-Carbon Low-Temperature Bainitic Steel: A Critical Analysis of a One-Step versus a Two-Step Treatment

Effect of Austempering on Mechanical Properties of Nb/V Microalloyed Bainitic Bearing Steel

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

Contact Info

Product

Resources

About