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Metals
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Bainite and Martensite Transformation in Steel
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Bainite and Martensite Transformation in Steel

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: closed (20 January 2020) | Viewed by 11686

Special Issue Editors

Prof. Stéphane Godet

E-Mail Website
Guest Editor
Materials Engineering, Characterization, Synthesis and Recycling (4MAT), Université libre de Bruxelles (ULB), 50 Avenue FD Roosevelt CP 165/63, 1050 Brussels, Belgium
Interests: alloy design; phase transformations; steels; additive manufacturing; textures; cristallography
Prof. Mohamed Gouné

E-Mail Website
Guest Editor
Université de Bordeaux, Bordeaux, France
Interests: phase transformation in steels; relationship between microstructure and mechanical properties; transformation interfaces

Special Issue Information

Dear Colleagues,

Although the discovery of martensite in steels dates back to 1890 and the work of German microscopist Adlof Martens, and although martensitic steels have been produced by mankind as early as 13 centuries BC, bainitic and martensitic transformations are still the topic of vivid research and vigorous debates.  This quest for a better understanding of the thermodynamics, kinetics and crystallography of those transformations in steels has opened the way to the development of new steel families that are becoming more and more relevant for the industrial world, the automotive industry in particular.

This special issue aims at reviewing the current challenges in the understanding, characterization and modeling of bainite and martensite in steels. It is devoted to the latest research in the development of innovative thermo-mechanical processing of complex-phase or multiphase steels. Fundamental research on the characterization of the thermodynamics, kinetics and crystallography of those transformations are also welcome.

Prof. Stéphane Godet
Prof. Mohamed Gouné
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Martensite
  • Bainite
  • Thermodynamics
  • Kinetics
  • Crystallography
  • Multiphase steels
  • Mechanical properties

Published Papers (3 papers)

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Research

16 pages, 4257 KiB  
Article
Bainite Transformation-Kinetics-Microstructure Characterization of Austempered 4140 Steel
by Jian G. Zhu, Xichen Sun, Gary C. Barber, Xue Han and Hao Qin
Metals 2020, 10(2), 236; https://doi.org/10.3390/met10020236 - 10 Feb 2020
Cited by 9 | Viewed by 5284
Abstract
Bainite transformation is a kinetic process that involves complex solid diffusion and phase structure evolution. This research systematically studies the bainite transformation of austempered 4140 steel in a wide range of isothermal temperatures, in which four bainite phases structures were generated: upper bainite; [...] Read more.
Bainite transformation is a kinetic process that involves complex solid diffusion and phase structure evolution. This research systematically studies the bainite transformation of austempered 4140 steel in a wide range of isothermal temperatures, in which four bainite phases structures were generated: upper bainite; mixed upper bainite and lower bainite; lower bainite and mixed lower bainite and martensite. The kinetics of bainite transformation has been described with a linear trend using an Avrami n-value. It was found that the bainitic ferrite sheaves grow with widthwise preference. The sheaves are stable when half-grown and are variable in length, due to austenite size limit or soft/hard impingement, or autocatalytic nucleation, or these conditions combined. The full-grown upper/lower bainite sheaves were found to be 1.9 μm/1.2 μm in width under the conditions of this study. Each individual bainite sheave is lath-like instead of wedge-like. The upper bainite sheaves mostly appear as broad-short-coarse lath, while the lower bainite sheaves appear as narrow-long-fine lath. The overall bainite transformation activation energy ranges from 50–167 kJ/mol. Full article
(This article belongs to the Special Issue Bainite and Martensite Transformation in Steel)
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15 pages, 5979 KiB  
Article
Effect of Austenitizing Temperature and Prior Martensite on Ultra-Fine Bainite Transformation Kinetics
by Zhiyong Li, Pengfei Li, Yang Luo, Xiyue Zhou, Liang Qi, Shengci Li and Zhigang Wang
Metals 2019, 9(12), 1309; https://doi.org/10.3390/met9121309 - 5 Dec 2019
Cited by 6 | Viewed by 2687
Abstract
An evaluation method for bainite transformation kinetics was established by theoretical derivation, dilatometric curve analysis, and microstructure observation. The isothermal transformation of ultra-fine bainite under different austenitizing temperatures and contents of prior martensite was studied using a DIL805L dilatometer. The kinetic parameters (activation [...] Read more.
An evaluation method for bainite transformation kinetics was established by theoretical derivation, dilatometric curve analysis, and microstructure observation. The isothermal transformation of ultra-fine bainite under different austenitizing temperatures and contents of prior martensite was studied using a DIL805L dilatometer. The kinetic parameters (activation energy Q*, autocatalytic factor λ, temperature rate constant κ, unit volume transformation rate, and the number density of nucleation sites Ni) of ultra-fine bainite transformation under different austenitizing temperatures and contents of prior martensite were calculated based on the displacement growth bainite dynamics model. It was found that the autocatalytic factor λ is linear with the austenite grain size d, and the number density of nucleation sites Ni is closely related to the average volume of the bainite subunit Vb. Moreover, the formation of prior martensite and its increase can increase the number of nucleation sites and the nucleation rate of the ultra-fine bainite; thus, the ultra-fine bainite transformation can be accelerated. Full article
(This article belongs to the Special Issue Bainite and Martensite Transformation in Steel)
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16 pages, 2616 KiB  
Article
Quantitative Assessment of the Time to End Bainitic Transformation
by Miguel A. Santajuana, Adriana Eres-Castellanos, Victor Ruiz-Jimenez, Sebastien Allain, Guillaume Geandier, Francisca G. Caballero and Carlos Garcia-Mateo
Metals 2019, 9(9), 925; https://doi.org/10.3390/met9090925 - 23 Aug 2019
Cited by 14 | Viewed by 3065
Abstract
Low temperature bainite consists of an intimate mixture of bainitic ferrite and retained austenite, usually obtained by isothermal treatments at temperatures close to the martensite start temperature and below the bainite start temperature. There is widespread belief regarding the extremely long heat treatments [...] Read more.
Low temperature bainite consists of an intimate mixture of bainitic ferrite and retained austenite, usually obtained by isothermal treatments at temperatures close to the martensite start temperature and below the bainite start temperature. There is widespread belief regarding the extremely long heat treatments necessary to achieve such a microstructure, but still there are no unified and objective criteria to determine the end of the bainitic transformation that allow for meaningful results and its comparison. A very common way to track such a transformation is by means of a high-resolution dilatometer. The relative change in length associated with the bainitic transformation has a very characteristic sigmoidal shape, with low transformation rates at the beginning and at end of the transformation but rapid in between. The determination of the end of transformation is normally subjected to the ability and experience of the “operator” and is therefore subjective. What is more, in the case of very long heat treatments, like those needed for low temperature bainite (from hours to days), differences in the criteria used to determine the end of transformation might lead to differences that might not be assumable from an industrial point of view. This work reviews some of the most common procedures and attempts to establish a general criterion to determine the end of bainitic transformation, based on the differential change in length (transformation rate) derived from a single experiment. The proposed method has been validated by means of the complementary use of hardness measurements, X-ray diffraction and in situ high energy X-ray diffraction. Full article
(This article belongs to the Special Issue Bainite and Martensite Transformation in Steel)
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