Effect of Austenitizing Temperature on Mechanical Properties of the Mixed Bainite - Martensite Microstructure in CrMoV Steel

Abbaszadeh, Parsa; Kheirandish, Shahram; Sadrnia, Hassan

doi:10.1590/1980-5373-mr-2017-0469

Cited by 15 publications

(8 citation statements)

References 23 publications

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“…The image obtained via scanning electron microscopy (SEM) (Fig. 6C) clearly shows transition carbides inside bainite grains, indicating the formation of lower bainite (LI et al ., 2010; Abbaszadeh et al ., 2017). Also, some carbides were precipitated in the whole martensite matrix, proving the tempering of martensite.…”

Section: Resultsmentioning

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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Section: Resultsmentioning

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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“…However, the mechanical properties of upper bainite-martensite decrease. Parsa Abbaszadeh [23] thought that the mixed microstructures containing 12-28% bainite showed higher yield strength than single martensitic because there is a plastic constraint effect induced by the surrounding relatively rigid martensite, leading to improved strength of bainite. The research above serves to study the effects of multiphase on the mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Ni on Bainite/Martensite Transformation and Mechanical Properties of Deposited Metals Obtained from Metal-Cored Wire

Wang

et al. 2021

Metals

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The multi-pass deposited metals were prepared by metal-cored wire with low (2.5 wt%) and high (4.0 wt%) Ni to research the effect of Ni on the bainite/martensite transformation. Results showed that deposited metals exhibited a multiphase structure comprised of bainite, martensite and residual austenite, which is not only explained from SEM/TEM, but also identified and quantified each phase from crystallographic structure through XRD and EBSD. With Ni content increasing, the fraction of martensite increases from 37% to 41%, and that of bainite decreases from 61% to 55% accordingly because 4% Ni element narrows the temperature range of the bainite transformation ~20 °C. The 7.8% residual austenite exhibited block and sheet in the deposited metal with low Ni, while the fraction of residual austenite was 3.26% as a film with high Ni, caused by different transformation mechanisms of bainite and martensite. The tensile strengths of deposited metals were 1042 ± 10 MPa (2.5% Ni) and 1040 ± 5 MPa (4% Ni), respectively. The yield strength of deposited metals with high Ni was 685 ± 18 MPa, which was higher than low Ni due to the high fraction of martensite. The impact values of deposited metals with high Ni content decreased because the volume fraction of bainite and residual austenite and area fraction of large-angle grain boundary were lower.

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“…The possibility of stabilizing austenite by controlling the carbon enrichment, during the partitioning step, differentiates the Q&P from the traditional QT process. Additionally, superior mechanical properties of Q&P steels have been obtained in comparison to steels with conventional heat treatment/microstructures such as bainitic or martensitic microstructures 10,12 .…”

Section: Introductionmentioning

confidence: 99%

Improvement of wear resistance in a pearlitic rail steel via quenching and partitioning processing

Masoumi

Echeverri

Tschiptschin

et al. 2019

Sci Rep

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Improvement of wear resistance and mechanical performance of rails used in heavy-haul railway are essential to reduce railroad maintenance costs. A novel heat treatment based on quenching and partitioning (Q&P) processing was proposed to improve the wear resistance of a hypereutectoid pearlitic rail. 50% of austenite was transformed into martensite under an interrupted quenching from full austenitization temperature to 140 °C. A multiphase microstructure resulted from the quenching and partitioning process, consisting of tempered martensite, bainite, retained austenite, and pearlite colonies. The partitioning step was performed in the range of 350–650 °C. Microstructure characteristics were investigated using scanning electron microscopy, microhardness measurements, X-ray and electron backscattered diffraction. Uniaxial tensile and pin-on-disc tests were also performed to evaluate the mechanical properties and wear resistance. The best combination of wear resistance and mechanical performance was obtained in samples partitioned at 450 and 550 °C, which may be applied in the railway industries.

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Effect of Austenitizing Temperature on Mechanical Properties of the Mixed Bainite - Martensite Microstructure in CrMoV Steel

Cited by 15 publications

References 23 publications

Multiple etchings methodology: a new approach in multiphase steel characterization

Multiple etchings methodology: a new approach in multiphase steel characterization

The Influence of Ni on Bainite/Martensite Transformation and Mechanical Properties of Deposited Metals Obtained from Metal-Cored Wire

Improvement of wear resistance in a pearlitic rail steel via quenching and partitioning processing

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