Special Issue "Bainite and Martensite: Developments and Challenges"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 May 2017)

Special Issue Editor

Guest Editor
Dr. Carlos Garcia-Mateo

Physical Metallurgy Department, Spanish National Center for Metallurgical Research, Madrid 28040, Spain
Website | E-Mail
Interests: phase transformations in steels; bainite; microstructural characterization; microstructure-mechanical properties relationships; alloy design

Special Issue Information

Dear Colleagues,

Nowadays, when modern high strength steels come to play, it is not strange to find that their microstructure contains austenite and either bainite or martensite, a combination of both, or more sophisticated variations such as Q&P and nanostructured bainitic steels.

There is no doubt that there are certain similarities in the mechanisms ruling such transformations, and therefore it is not surprising that parameters at play controlling the mechanical properties also overlap.

The development of new and powerful scientific techniques and equipment (EBSD, APT, HRTEM, etc.) allow us to gain fundamental insights that help to establish some of the principles by which those microstructures are known. The developments accompanying such findings lead to further developments and intensive research providing the required metallurgical support.

There is a very significant number of publications and some scattered conferences and workshops devoted to these type steels. However, there is no forum that brings together the latest developments, taking place in the framework of these microstructures and their properties.

Papers on recent advances and review articles, particularly related to the most challenging aspects of the use of bainitic and martensitic microstructures, in any of their forms, are invited for inclusion in this Special Issue on "Bainite and Martensite: Developments and Challenges".

Dr. Carlos Garcia-Mateo
Guest Editor

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 papers will be 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 1000 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

  • Phase transformation
  • Modelling
  • Alloy and process design
  • Thermal treatment
  • Mechanical and in-use properties
  • Crystallography
  • Microstructural (advanced) characterization

Published Papers (10 papers)

View options order results:
result details:
Displaying articles 1-10
Export citation of selected articles as:

Research

Jump to: Review, Other

Open AccessArticle In-Situ Investigation of Strain-Induced Martensitic Transformation Kinetics in an Austenitic Stainless Steel by Inductive Measurements
Metals 2017, 7(7), 271; doi:10.3390/met7070271
Received: 31 May 2017 / Revised: 10 July 2017 / Accepted: 12 July 2017 / Published: 13 July 2017
PDF Full-text (5234 KB) | HTML Full-text | XML Full-text
Abstract
An inductive sensor developed by Philips ATC has been used to study in-situ the austenite (γ) to martensite (α′) phase transformation kinetics during tensile testing in an AISI 301 austenitic stainless steel. A correlation between the sensor output signal and the volume fraction
[...] Read more.
An inductive sensor developed by Philips ATC has been used to study in-situ the austenite (γ) to martensite (α′) phase transformation kinetics during tensile testing in an AISI 301 austenitic stainless steel. A correlation between the sensor output signal and the volume fraction of α′-martensite has been found by comparing the results to the ex-situ characterization by magnetization measurements, light optical microscopy, and X-ray diffraction. The sensor has allowed for the observation of the stepwise transformation behavior, a not-well-understood phenomena that takes place in large regions of the bulk material and that so far had only been observed by synchrotron X-ray diffraction. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Open AccessArticle Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7
Metals 2017, 7(7), 258; doi:10.3390/met7070258
Received: 23 May 2017 / Revised: 26 June 2017 / Accepted: 3 July 2017 / Published: 7 July 2017
PDF Full-text (5257 KB) | HTML Full-text | XML Full-text
Abstract
Ultrahigh strength steel 56NiCrMoV7 was austempered at 270 °C for different durations in order to investigate the microstructure evolution, carbon partitioning behaviour and hardness property. Detailed microstructure has been characterised using optical microscopy and field emission gun scanning electron microscopy. A newly developed
[...] Read more.
Ultrahigh strength steel 56NiCrMoV7 was austempered at 270 °C for different durations in order to investigate the microstructure evolution, carbon partitioning behaviour and hardness property. Detailed microstructure has been characterised using optical microscopy and field emission gun scanning electron microscopy. A newly developed X-ray diffraction method has been employed to dissolve the bainitic/martensitic ferrite phase as two sub-phases of different tetragonal ratios, which provides quantitative analyses of the carbon partitioning between the resultant ferrites and the retained austenite. The results show that, a short-term austempering treatment was in the incubation period of the bainite transformation, which resulted in maximum hardness being equivalent to the oil-quenching treatment. The associated microstructure comprises fine carbide-free martensitic and bainitic ferrites of supersaturated carbon contents as well as carbon-rich retained austenite. In particular, the short-term austempering treatment helped prevent the formation of lengthy martensitic laths as those being found in the microstructure of oil-quenched sample. When the austempering time was increased from 20 to 80 min, progressive decrease of the hardness was associated with the evolution of the microstructure, including progressive coarsening of bainitic ferrite, carbide precipitating inside high-carbon bainitic ferrite and its subsequent decarbonisation. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Open AccessFeature PaperArticle High-Temperature Tempered Martensite Embrittlement in Quenched-and-Tempered Offshore Steels
Metals 2017, 7(7), 253; doi:10.3390/met7070253
Received: 31 May 2017 / Revised: 23 June 2017 / Accepted: 3 July 2017 / Published: 6 July 2017
PDF Full-text (10235 KB) | HTML Full-text | XML Full-text
Abstract
Embrittlement induced by high-temperature tempering was investigated in two quenched-and-tempered offshore steels. Electron backscattering diffraction and analysis of Kernel average misorientation were applied to study the coalescence of martensite; transmission Kikuchi diffraction coupled with compositional mapping was used to characterize the martensite/austenite (M/A)
[...] Read more.
Embrittlement induced by high-temperature tempering was investigated in two quenched-and-tempered offshore steels. Electron backscattering diffraction and analysis of Kernel average misorientation were applied to study the coalescence of martensite; transmission Kikuchi diffraction coupled with compositional mapping was used to characterize the martensite/austenite (M/A) phases. It is suggested that the formation of lenticular martensite along prior austenite grain boundaries or packet boundaries primarily explains the embrittlement in conventional S690Q steel, which has a higher carbon content. This embrittlement can be cured by additional heat treatment to decompose martensite into ferrite and cementite. In a newly designed NiCu steel with reduced carbon content, new lath martensite formed along interlath or inter-block boundaries of prior martensite. This microstructure is less detrimental to the impact toughness of the steel. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Open AccessFeature PaperArticle Effect of Ausforming Temperature on the Microstructure of G91 Steel
Metals 2017, 7(7), 236; doi:10.3390/met7070236
Received: 18 May 2017 / Revised: 20 June 2017 / Accepted: 23 June 2017 / Published: 27 June 2017
PDF Full-text (13255 KB) | HTML Full-text | XML Full-text
Abstract
The development of thermomechanical treatments (TMT) has a high potential for improving creep-strength in 9Cr-1Mo ferritic/martensitic steel (ASTM T/P91) to operate at temperatures beyond 600 °C. To maximize the number of nanoscale MX precipitates, an ausforming procedure has been used to increase the
[...] Read more.
The development of thermomechanical treatments (TMT) has a high potential for improving creep-strength in 9Cr-1Mo ferritic/martensitic steel (ASTM T/P91) to operate at temperatures beyond 600 °C. To maximize the number of nanoscale MX precipitates, an ausforming procedure has been used to increase the number of nucleation sites for precipitation inside the martensite lath. Relative to standard heat treatments (consisting of austenitization at about 1040 °C followed by tempering at about 730 °C) this processing concept has enabled achieving a microstructure containing approximately three orders of magnitude higher number density of MX precipitates having a size around four times smaller in ASTM T/P91 steel. On the other hand; this TMT has little effect on the size and number density of M23C6 particles. The optimized microstructure produced by this TMT route proposed is expected to improve the creep strength of this steel. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Figure 1

Open AccessFeature PaperArticle The Nitrocarburising Response of Low Temperature Bainite Steel
Metals 2017, 7(7), 234; doi:10.3390/met7070234
Received: 31 May 2017 / Revised: 21 June 2017 / Accepted: 21 June 2017 / Published: 26 June 2017
PDF Full-text (7736 KB) | HTML Full-text | XML Full-text
Abstract
The nitrocarburising response of low transformation temperature ultrafine and nanoscale bainitic steel was investigated and compared with martensite and pearlite from the same steel composition. It was found that the retained austenite content of the bainitic steel dictated the core hardness after nitrocarburising.
[...] Read more.
The nitrocarburising response of low transformation temperature ultrafine and nanoscale bainitic steel was investigated and compared with martensite and pearlite from the same steel composition. It was found that the retained austenite content of the bainitic steel dictated the core hardness after nitrocarburising. The refined bainitic structure showed improvements in the nitriding depth and hardness of the nitrocarburised layer, compared to coarser grained martensitic and pearlitic structures, possibly due to the fine structure and the distribution of nitride forming elements. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Figure 1

Open AccessArticle Effects of Q&P Processing Conditions on Austenite Carbon Enrichment Studied by In Situ High-Energy X-ray Diffraction Experiments
Metals 2017, 7(7), 232; doi:10.3390/met7070232
Received: 13 May 2017 / Revised: 10 June 2017 / Accepted: 16 June 2017 / Published: 22 June 2017
PDF Full-text (1849 KB) | HTML Full-text | XML Full-text
Abstract
We report the first ultra-fast time-resolved quantitative information on the quenching and partitioning process of conventional high-strength steel by an in situ high-energy X-ray diffraction (HEXRD) experiment. The time and temperature evolutions of phase fractions, their carbon content, and internal stresses were determined
[...] Read more.
We report the first ultra-fast time-resolved quantitative information on the quenching and partitioning process of conventional high-strength steel by an in situ high-energy X-ray diffraction (HEXRD) experiment. The time and temperature evolutions of phase fractions, their carbon content, and internal stresses were determined and discussed for different process parameters. It is shown that the austenite-to-martensite transformation below the martensite start temperature Ms is followed by a stage of fast carbon enrichment in austenite during isothermal holding at both 400 and 450 °C. The analysis proposed supports the concurrent bainite transformation and carbon diffusion from martensite to austenite as the main mechanisms of this enrichment. Furthermore, we give evidence that high hydrostatic tensile stresses in austenite are produced during the final quenching, and must be taken into account for the estimation of the carbon content in austenite. Finally, a large amount of carbon is shown to be trapped in the microstructure. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Open AccessArticle Evaluating Strengthening and Impact Toughness Mechanisms for Ferritic and Bainitic Microstructures in Nb, Nb-Mo and Ti-Mo Microalloyed Steels
Metals 2017, 7(2), 65; doi:10.3390/met7020065
Received: 10 February 2017 / Revised: 17 February 2017 / Accepted: 17 February 2017 / Published: 22 February 2017
PDF Full-text (5419 KB) | HTML Full-text | XML Full-text
Abstract
Low carbon microalloyed steels show interesting commercial possibilities by combining different “micro”-alloying elements when high strength and low temperature toughness properties are required. Depending on the elements chosen for the chemistry design, the mechanisms controlling the strengths and toughness may differ. In this
[...] Read more.
Low carbon microalloyed steels show interesting commercial possibilities by combining different “micro”-alloying elements when high strength and low temperature toughness properties are required. Depending on the elements chosen for the chemistry design, the mechanisms controlling the strengths and toughness may differ. In this paper, a detailed characterization of the microstructural features of three different microalloyed steels, Nb, Nb-Mo and Ti-Mo, is described using mainly the electron backscattered diffraction technique (EBSD) as well as transmission electron microscopy (TEM). The contribution of different strengthening mechanisms to yield strength and impact toughness is evaluated, and its relative weight is computed for different coiling temperatures. Grain refinement is shown to be the most effective mechanism for controlling both mechanical properties. As yield strength increases, the relative contribution of precipitation strengthening increases, and this factor is especially important in the Ti-Mo microalloyed steel where different combinations of interphase and random precipitation are detected depending on the coiling temperature. In addition to average grain size values, microstructural heterogeneity is considered in order to propose a new equation for predicting ductile–brittle transition temperature (DBTT). This equation considers the wide range of microstructures analyzed as well as the increase in the transition temperature related to precipitation strengthening. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Figure 1

Open AccessArticle Phase Equilibrium and Austenite Decomposition in Advanced High-Strength Medium-Mn Bainitic Steels
Metals 2016, 6(10), 248; doi:10.3390/met6100248
Received: 15 September 2016 / Revised: 11 October 2016 / Accepted: 14 October 2016 / Published: 20 October 2016
PDF Full-text (7362 KB) | HTML Full-text | XML Full-text
Abstract
The work addresses the phase equilibrium analysis and austenite decomposition of two Nb-microalloyed medium-Mn steels containing 3% and 5% Mn. The pseudobinary Fe-C diagrams of the steels were calculated using Thermo-Calc. Thermodynamic calculations of the volume fraction evolution of microstructural constituents vs. temperature
[...] Read more.
The work addresses the phase equilibrium analysis and austenite decomposition of two Nb-microalloyed medium-Mn steels containing 3% and 5% Mn. The pseudobinary Fe-C diagrams of the steels were calculated using Thermo-Calc. Thermodynamic calculations of the volume fraction evolution of microstructural constituents vs. temperature were carried out. The study comprised the determination of the time-temperature-transformation (TTT) diagrams and continuous cooling transformation (CCT) diagrams of the investigated steels. The diagrams were used to determine continuous and isothermal cooling paths suitable for production of bainite-based steels. It was found that the various Mn content strongly influences the hardenability of the steels and hence the austenite decomposition during cooling. The knowledge of CCT diagrams and the analysis of experimental dilatometric curves enabled to produce bainite-austenite mixtures in the thermomechanical simulator. Light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to assess the effect of heat treatment on morphological details of produced multiphase microstructures. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Figure 1

Review

Jump to: Research, Other

Open AccessReview Transferring Nanoscale Bainite Concept to Lower C Contents: A Perspective
Metals 2017, 7(5), 159; doi:10.3390/met7050159
Received: 27 March 2017 / Revised: 16 April 2017 / Accepted: 28 April 2017 / Published: 4 May 2017
PDF Full-text (3453 KB) | HTML Full-text | XML Full-text
Abstract
The major strengthening mechanisms in bainitic steels arise from the bainitic ferrite plate thickness rather than the length, which primarily determines the mean free slip distance. Both the strength of the austenite from where the bainite grows and the driving force of the
[...] Read more.
The major strengthening mechanisms in bainitic steels arise from the bainitic ferrite plate thickness rather than the length, which primarily determines the mean free slip distance. Both the strength of the austenite from where the bainite grows and the driving force of the transformation, are the two factors controlling the final scale of the bainitic microstructure. Usually, those two parameters can be tailored by means of selection of chemical composition and transformation temperature. However, there is also the possibility of introducing plastic deformation on austenite and prior to the bainitic transformation as a way to enhance both the austenite strength and the driving force for the transformation; the latter by introducing a mechanical component to the free energy change. This process, known as ausforming, has awoken a great deal of interest and it is the object of ongoing research with two clear aims. First, an acceleration of the sluggish bainitic transformation observed typically in high C steels (0.7–1 wt. %) transformed at relatively low temperatures. Second, to extend the concept of nanostructured bainite from those of high C steels to much lower C contents, 0.4–0.5 wt. %, keeping a wider range of applications in view. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Figure 1

Other

Jump to: Research, Review

Open AccessFeature PaperTechnical Note Tensile Ductility of Nanostructured Bainitic Steels: Influence of Retained Austenite Stability
Metals 2017, 7(1), 31; doi:10.3390/met7010031
Received: 19 December 2016 / Revised: 9 January 2017 / Accepted: 16 January 2017 / Published: 23 January 2017
PDF Full-text (759 KB) | HTML Full-text | XML Full-text
Abstract
High silicon (>1.5%) steels with different compositions were isothermally transformed to bainite at 220 and 250 °C to produce what is often referred to as nanostructured bainite. Interrupted tensile tests were carried out and the retained austenite was measured as a function of
[...] Read more.
High silicon (>1.5%) steels with different compositions were isothermally transformed to bainite at 220 and 250 °C to produce what is often referred to as nanostructured bainite. Interrupted tensile tests were carried out and the retained austenite was measured as a function of strain. Results were correlated with tensile ductility. The role of retained austenite stability is remarkably underlined as strongly affecting the propensity to brittle failure, but also the tensile ductility. A simple quantitative relationship is proposed that clearly delimitates the different behaviours (brittle/ductile) and correlates well with the measured ductility. Conclusions are proposed as to the role of retained austenite fraction and the existence of a threshold value associated with tensile rupture. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Figure 1

Journal Contact

MDPI AG
Metals Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
E-Mail: 
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Metals Edit a special issue Review for Metals
logo
loading...
Back to Top