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Metals
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Medium-Mn Steels, a Promising Type of the 3rd Generation Steels
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Medium-Mn Steels, a Promising Type of the 3rd Generation Steels

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

Deadline for manuscript submissions: closed (31 March 2019) | Viewed by 29255

Special Issue Editor

Prof. L. Pentti Karjalainen

E-Mail Website1 Website2
Guest Editor
Centre for Advanced Steels Research, University of Oulu, FI-90014 Oulu, Finland
Interests: advanced steels; microstructures; mechanical properties; testing; fatigue; applications

Special Issue Information

Dear Colleagues,

As demonstrated more than a decade ago, ferrite-austenite and martensite-austenite steel microstructures can provide enhanced strength-ductility combinations, improved with the increasing austenite fraction. In addition to the amount of austenite, its stability under deformation is of high importance concerning the transformation-induced plasticity and possible twinning-induced plasticity effects and thereby high ductility.

Fully austenitic TWIP-steels have outstanding properties in terms of strength and ductility combination, but there is a serious problem in terms of mass production of these steel: the high costs not only of the raw materials, but also of the production process. Further, certain embrittlement phenomena have limited their application. For these reasons, the Mn content in the steel needs to be reduced to an industrially appropriate level.

Indeed, medium-Mn steels containing 3%–11% Mn have reached much attention lately. Excellent properties of medium-Mn steels were invented and reported already in the early 1970s, but the interest has recently exploded with respect, particularly, to automotive applications. As such, a material, medium-Mn high-strength and ultra-high strength steels was developed in order to enable lightweight car body design and improved passenger safety features. However, the optimization of medium-Mn steel has, up to now, not been fully addressed due to the complexity of their mechanical properties, which are sensitively dependent on their chemical composition and processing conditions. Despite the apparent success in achieving the desired base metal mechanical properties, very few studies have been performed on the effects of fabrication processes, such as welding, forming, etc.

The exploitation of medium-Mn steels is far from mature and the subject is both scientifically and technologically fascinating. In order to provide an overview on the current state-of-the-art of these advanced steels, a Special Issue of Metals is commissioned and we invite contributions covering different aspects of medium-Mn steels.

Prof. L. Pentti Karjalainen
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 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

  • Medium-Mn steel
  • Alloying
  • Processing
  • Austenite
  • Retained austenite stability
  • Strength
  • Ductility
  • Fabrication properties
  • Automotive applications

Published Papers (7 papers)

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Research

19 pages, 4846 KiB  
Article
Microstructure–Property Relationships in Thermomechanically Processed Medium-Mn Steels with High Al Content
by Adam Grajcar, Andrzej Kilarski and Aleksandra Kozlowska
Metals 2018, 8(11), 929; https://doi.org/10.3390/met8110929 - 09 Nov 2018
Cited by 31 | Viewed by 3529
Abstract
Detailed studies on microstructure–property relationships of thermomechanically processed medium-Mn steels with various manganese contents were carried out. Microscopic techniques of different resolution (LM, SEM, TEM) and X-Ray diffraction methods were applied. Static tensile tests were performed to characterize mechanical properties of the investigated [...] Read more.
Detailed studies on microstructure–property relationships of thermomechanically processed medium-Mn steels with various manganese contents were carried out. Microscopic techniques of different resolution (LM, SEM, TEM) and X-Ray diffraction methods were applied. Static tensile tests were performed to characterize mechanical properties of the investigated steels and to determine the tendency of retained austenite to strain-induced martensitic transformation. Obtained results allowed to characterize the microstructural aspects of strain-induced martensitic transformation and its effect on the mechanical properties. It was found that the mechanical stability of retained austenite depends significantly on the manganese content. An increase in manganese content from 3.3% to 4.7% has a significant impact on the microstructure, stability of γ phase and mechanical properties of the investigated steels. The initial amount of retained austenite was higher for the 3Mn-1.5Al steel in comparison to 5Mn-1.5%Al steel—17% and 11%, respectively. The mechanical stability of retained austenite is significantly affected by the morphology of this phase. Full article
(This article belongs to the Special Issue Medium-Mn Steels, a Promising Type of the 3rd Generation Steels)
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9 pages, 3343 KiB  
Article
Tensile Deformation Behavior of Medium Manganese Steels with High Carbon Concentrations and Austenitic Microstructures
by Guoqing Luan, Olena Volkova and Javad Mola
Metals 2018, 8(11), 902; https://doi.org/10.3390/met8110902 - 04 Nov 2018
Cited by 2 | Viewed by 2690
Abstract
Tensile properties of the Fe–1.44C–8Mn–1.9Al (mass %) steel with a fully austenitic microstructure, obtained by rapid quenching from the austenite range, was determined at room temperature. Tensile tests were performed using specimens prepared in two different routes involving an exchanged sequence of machining [...] Read more.
Tensile properties of the Fe–1.44C–8Mn–1.9Al (mass %) steel with a fully austenitic microstructure, obtained by rapid quenching from the austenite range, was determined at room temperature. Tensile tests were performed using specimens prepared in two different routes involving an exchanged sequence of machining and heat treatment as the last processing steps prior to tensile tests. In spite of the occurrence of deformation twinning, total tensile elongations in both processing routes remained below 18%. Abrupt stress drops during tensile tests suggested the occurrence of discontinuities in tensile specimens. Detailed examination of the fracture surface indicated a mixed intergranular–transgranular fracture mode. Furthermore, a high density of surface cracks was observed near the outer surface in the gauge section of fractured tensile specimens. The origin of surface cracks could not be identified. The coincidence of surface cracks with the grain boundaries, especially those nearly perpendicular to the tensile direction, is thought to be responsible for the accelerated grain boundary decohesion and the premature fracture of tensile specimens. Full article
(This article belongs to the Special Issue Medium-Mn Steels, a Promising Type of the 3rd Generation Steels)
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10 pages, 3557 KiB  
Article
Microstructural Analysis and Tribology Behavior of a Medium-Mn Steel with Mo
by Benito Del Río López, Ana García Diez, José Luís Mier Buenhombre, Carolina Camba Fabal and Almudena Filgueira Vizoso
Metals 2018, 8(10), 745; https://doi.org/10.3390/met8100745 - 21 Sep 2018
Cited by 3 | Viewed by 2579
Abstract
This paper presents an alternative to the materials traditionally used in the manufacture of coal mills for coating wedges. For this purpose, we designed and tested ten new austenitic steels with medium manganese content. The thermal structural stability and hardness were evaluated after [...] Read more.
This paper presents an alternative to the materials traditionally used in the manufacture of coal mills for coating wedges. For this purpose, we designed and tested ten new austenitic steels with medium manganese content. The thermal structural stability and hardness were evaluated after different heat treatments. The steels were subjected to hyperquenching and tempering between 100 and 900 °C. A metallographic analysis of each sample was then performed to determine their thermal stability, and the Brinell hardness was measured. Later, wedges of two alternatives and reference-material alloys were manufactured and installed in three types of mills. Their mass loss was determined after 25 months and at an intermediate time during that period. One steel was selected as an alternative material. Full article
(This article belongs to the Special Issue Medium-Mn Steels, a Promising Type of the 3rd Generation Steels)
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18 pages, 28885 KiB  
Article
Microstructure, Mechanical Properties and Welding of Low Carbon, Medium Manganese TWIP/TRIP Steel
by Pavel Podany, Christopher Reardon, Martina Koukolikova, Radek Prochazka and Ales Franc
Metals 2018, 8(4), 263; https://doi.org/10.3390/met8040263 - 12 Apr 2018
Cited by 15 | Viewed by 4626
Abstract
Manganese twinning induced plasticity (TWIP) steels are attractive materials for the automotive industry thanks to their combination of strength and excellent toughness. This article deals with basic microstructural and mechanical properties of sheet metal of two heats of low-carbon medium-manganese steel with different [...] Read more.
Manganese twinning induced plasticity (TWIP) steels are attractive materials for the automotive industry thanks to their combination of strength and excellent toughness. This article deals with basic microstructural and mechanical properties of sheet metal of two heats of low-carbon medium-manganese steel with different aluminium levels. Microstructure observation was carried out using optical and scanning electron microscopy. Electron backscatter diffraction (EBSD) and X-ray diffraction were used for phase analysis. In an experiment that focused on the weldability of both materials, sheet metals were laser-welded using various laser power settings, with and without shielding gas. Various combinations of joints between materials of the two heats and sheet metal conditions were tested (work-hardened upon cold rolling + annealed). Mechanical properties of the weld joints were determined using miniature tensile testing and conventional hardness measurement. The strengths of miniature specimens of the weld metal were very close to the strength of the base material. Full article
(This article belongs to the Special Issue Medium-Mn Steels, a Promising Type of the 3rd Generation Steels)
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13 pages, 9506 KiB  
Article
Microstructure and Tensile-Shear Properties of Resistance Spot-Welded Medium Mn Steel
by Qiang Jia, Lei Liu, Wei Guo, Yun Peng, Guisheng Zou, Zhiling Tian and Y. Norman Zhou
Metals 2018, 8(1), 48; https://doi.org/10.3390/met8010048 - 11 Jan 2018
Cited by 45 | Viewed by 5023
Abstract
The medium Mn steels are gaining increasing attention due to their excellent combination of mechanical properties and material cost. A cold-rolled 0.1C5Mn medium Mn steel with a ferrite matrix plus metastable austenite duplex microstructure was resistance spot-welded with various welding currents and times. [...] Read more.
The medium Mn steels are gaining increasing attention due to their excellent combination of mechanical properties and material cost. A cold-rolled 0.1C5Mn medium Mn steel with a ferrite matrix plus metastable austenite duplex microstructure was resistance spot-welded with various welding currents and times. The nugget size rose with the increase of heat input, but when the welding current exceeded the critical value, the tensile-shear load increased slowly and became unstable due to metal expulsion. The fusion zone exhibited a lath martensite microstructure, and the heat-affected zone was composed of a ferrite/martensite matrix with retained austenite. The volume fraction of retained austenite decreased gradually from the base metal to the fusion zone, while the microhardness presented a reverse varying trend. Interfacial failure occurred along the interface of the steel sheets with lower loading capacity. Sufficient heat input along with serious expulsion brought about high stress concentration around the weld nugget, and the joint failed in partial interfacial mode. Pull-out failure was absent in this study. Full article
(This article belongs to the Special Issue Medium-Mn Steels, a Promising Type of the 3rd Generation Steels)
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27514 KiB  
Article
Effects of Phase Evolution on Mechanical Properties of Laser-Welded Ferritic Fe-Al-Mn-C Steel
by Minjung Kang, Young-Min Kim, Heung Nam Han and Cheolhee Kim
Metals 2017, 7(12), 523; https://doi.org/10.3390/met7120523 - 24 Nov 2017
Cited by 6 | Viewed by 4230
Abstract
In the present study, the evolution of microstructure in laser-welded joints of ferrite-based dual-phase Fe-Al-Mn-C steel sheets was analyzed and its effect on the mechanical properties of the joints was investigated. Laser welding was performed using different powers and welding speeds to attain [...] Read more.
In the present study, the evolution of microstructure in laser-welded joints of ferrite-based dual-phase Fe-Al-Mn-C steel sheets was analyzed and its effect on the mechanical properties of the joints was investigated. Laser welding was performed using different powers and welding speeds to attain different heat inputs. Electron backscatter diffraction (EBSD) examinations and hardness measurements were used to characterize the microstructure of the welds. The tensile properties were found to depend on the heat input, but joint strength exceeding that of the base metal (BM) were obtained at low heat inputs. However, the fracture location shifted from the base metal to the heat-affected zone (HAZ) as the heat input was increased. The HAZ consisted of a mixture of austenite, ferrite and martensite, and its width increased with increasing the heat input. It was supposed that the incompatibility between the ferrite, austenite and martensite phases led to early void formation and fracturing of the phase interfaces in the wide HAZ. Full article
(This article belongs to the Special Issue Medium-Mn Steels, a Promising Type of the 3rd Generation Steels)
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13687 KiB  
Article
Microstructures and Mechanical Properties of 7Mn Steel Manufactured by Different Rolling Processes
by Bin Hu and Haiwen Luo
Metals 2017, 7(11), 464; https://doi.org/10.3390/met7110464 - 01 Nov 2017
Cited by 21 | Viewed by 5038
Abstract
We investigated both the microstructures and tensile properties of 7Mn steel, which was either hot-rolled, warm-rolled or cold-rolled before intercritical annealing at 700 °C for 5 h. It can be concluded that the warm-rolled and annealed microstructures are a kind of mixture of [...] Read more.
We investigated both the microstructures and tensile properties of 7Mn steel, which was either hot-rolled, warm-rolled or cold-rolled before intercritical annealing at 700 °C for 5 h. It can be concluded that the warm-rolled and annealed microstructures are a kind of mixture of hot rolled and cold rolled ones. They are composed of ferrite and retained austenite, the latter having a wide size distribution and two types of morphologies: equiaxed and lamellar. These retained austenite grains are expected to transform to martensite in a more sustainable way—the warm-rolled and annealed steel exhibits the best combination of ultimate tensile strength and total elongation among the three studied steels and a shorter yield point elongation than the cold-rolled one. Full article
(This article belongs to the Special Issue Medium-Mn Steels, a Promising Type of the 3rd Generation Steels)
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