Effect of bainitic transformation during BQ&amp;P process on the mechanical properties in an ultrahigh strength Mn-Si-Cr-C steel

Gui, Xuchun; Gao, Guhui; Guo, Hongjian; Zhao, Feifan; Tan, Zhunli; Bai, Bin

doi:10.1016/j.msea.2016.12.097

Cited by 59 publications

(21 citation statements)

References 44 publications

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“…This is followed by a partitioning step at T q or higher than T q to promote carbon diffusion from supersaturated martensite to untransformed austenite, thereby stabilizing RA to room temperature . In our previous studies, we introduced the Q&P process in isothermal bainitic transformation in Mn–Si–Cr medium‐carbon steel. The study indicated that the blocky austenite phase was successfully converted to filmy RA and carbon‐depleted martensite.…”

Section: Introductionmentioning

confidence: 99%

Bainitic Austempering Incorporating Quenching and Partitioning for Favorable Tuning of Microstructure and Mechanical Properties

Gao

Tan

Luo

et al. 2020

steel research int.

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A novel aspect of combining bainitic austempering with quenching and the partitioning process is addressed herein to obtain a favorable microstructure with desired mechanical properties. In this regard, Mn-Si-Cr-Al steel is first intercritically annealed at 840 C and quenched to 140 C after isothermal treatment at 360 C for 15 min and then partitioned at 360 C for 30 min. Multiphase microstructure containing ferrite, bainite, martensite, and retained austenite (RA) is obtained. Uniform elongation and total elongation increase appreciably from 11.5% to 20.5% and 21.0% to 28.3%, respectively, while maintaining nearidentical levels of tensile strength, compared with traditional bainitic austempering. The significant enhancement of tensile properties is attributed to the increase in volume fraction and mechanical stability of RA.

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Section: Introductionmentioning

confidence: 99%

Bainitic Austempering Incorporating Quenching and Partitioning for Favorable Tuning of Microstructure and Mechanical Properties

Gao

Tan

Luo

et al. 2020

steel research int.

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“…Researchers (Alberto & Santos, 2013;Zhao et al, 2016;Hidalgo et al, 2017) have shown the possibility of obtaining carbide-free bainite from different processing routes such as austempering below-Ms. Others included a tempering step after the Q&P treatment in order to achieve better mechanical properties (Wang et al, 2009;Zhong et al, 2011;Jafari et al, 2018). The quenching-partitioningtempering (QPT), quenching and partitioning with a prior martensite microstructure (Ding et al, 2014) and the Bainite quenching and partitioning (BQ&P) (Gui et al, 2017) are examples of innovations. These processes have resulted in different microstructures, resulting in the presence of phases including martensite, ferrite, bainite and retained austenite.…”

Section: Introductionmentioning

confidence: 99%

Multiple etchings methodology: a new approach in multiphase steel characterization

Mendonça

Nogueira

Lovo

et al. 2020

Journal of Microscopy

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Summary Following the first and second generations, the challenge in obtaining a better balance between strength and elongation is still the main characteristic of the third generation of advanced high‐strength steels (AHSS). With this, the use of multiphase microstructures has increased over the last few years. It can be difficult to characterize all the phases with only optical microscopy (OM), so the use of scanning electron microscopy (SEM) is essential for accuracy in cases where researchers lack experience. To expand the possibilities, this research proposed a new approach that would allow experienced researchers to characterize multiphase steels using only OM. A high silicon steel was austempered slightly below martensite start (Ms) temperature for three different time periods in order to obtain different quantities of martensite, bainite and retained austenite. X‐ray diffraction was carried out in order to confirm and obtain retained austenite volume fractions, and the results indicated that shorter holding times were not enough to enrich and stabilize retained austenite. Then, each samples was etched with four different etchants. Results showed that the new multiple etchings methodology (MEM) allowed a better visualization of all the phases when viewed together. Beraha martensitc revealed nontempered martensitic microstructures. Sodium metabisulfite revealed retained austenite. LePera and Nital were the best at revealing the evolution of the microstructure over time, even with the changes which occurred due to martensite tempering. SEM images confirmed the results obtained via MEM. Lay Description For improving safety, environmental protection, mechanical resistance and others issues, many different steel grades have been studied. These grades were named depending on their mechanical properties. The current generation is the third, which is still searching for one of the main antagonists in material science: the best balance between mechanical resistance (how strong it is) and elongation (how long it can be stretched to). In order to achieve this goal, many researchers are studying variations in the production processes. During production, the materials are able to internally change their basic microstructure, named phases. In the past, steels were usually produced to have only a few phases. Today's advanced high strength steels (AHSS) can have many. Each of these phases has its own characteristics. The main focus of this research was to give a new way of identify these phases using an optical microscope. For revealing these phases, etchants are normally used. The etchants used in this research are capable of tinting each of these phases with a different colour or tone. So the purpose of this work was to suggest a new approach in order to allow for more precise identification of the phases in the steel. The results were positive, showing that looking at the samples as a whole is better than the traditional methods. Also, different etchants’ characteristics were observed during the changes obtained by thi...

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“…Another approach is to develop thermo-mechanically rolled fine-grained steel with a mixed microstructure consisting of martensite and/or bainite and a considerable amount of stabilized retained austenite (RA) [11,12]. In the last few years, many reports about the development of quenching and partitioning (Q&P) processes for the production of heat-treated steel with the optimal combination of high strength and ductility [13][14][15][16][17][18][19] can be found. All studies emphasize the key role of RA and its morphology, size, and distribution.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Retained Austenite in Fine Grained Inductive Heat Treated Spring Steel

et al. 2019

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Advanced thermomechanical hot rolling is becoming a widely used technology for the production of fine-grained spring steel. Different rapid phase transformations during the inductive heat treatment of such steel causes the inhomogeneous mixture of martensitic, bainitic, and austenitic phases that affects the service properties of the steel. An important task is to assess the amount of retained austenite and its distribution over the cross-section of the inductive quenched and tempered wire in order to evaluate the mechanical properties of the material. Three different analytical methods were used for the comparative quantitative assessment of the amount of retained austenite in both the core and rim areas of the sample cross-section: neutron diffraction—for the bulk of the material, Mössbauer spectroscopy—for measurement in a surface layer, and the metallographic investigations carried by the EBSD. The methods confirmed the excessive amount of retained austenite in the core area that could negatively affect the plasticity of the material.

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Effect of bainitic transformation during BQ&P process on the mechanical properties in an ultrahigh strength Mn-Si-Cr-C steel

Cited by 59 publications

References 44 publications

Bainitic Austempering Incorporating Quenching and Partitioning for Favorable Tuning of Microstructure and Mechanical Properties

Bainitic Austempering Incorporating Quenching and Partitioning for Favorable Tuning of Microstructure and Mechanical Properties

Multiple etchings methodology: a new approach in multiphase steel characterization

Assessment of Retained Austenite in Fine Grained Inductive Heat Treated Spring Steel

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