Special Issue "Performance of Mechanical Properties of Ultrahigh-Strength Ferrous Steels Related to Strain-Induced Transformation"

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

Deadline for manuscript submissions: 30 September 2019

Special Issue Editor

Guest Editor
Prof. Dr. Koh-ichi Sugimoto

Department of Mechanical Systems Engineering, Shinshu University, 3-1-1 Asahi, Matsumoto 390-0802, Japan
Website 1 | Website 2 | E-Mail
Phone: +81-26-269-5114/+81-26-269-5109
Interests: structural steels and alloys; composites; microstructure; mechanical property; micromechanics; heat-treatment; thermo-mechanical process; cold- and hot stamping; forging; welding; surface treatment

Special Issue Information

Dear Colleagues,

This Special Issue of Metals is dedicated to advanced ultrahigh-strength ferrous steels related to the strain-induced martensite transformation (or transformation-induced plasticity) of metastable retained austenite. Ferrous steels, such as Transformation-Induced Plasticity (TRIP)-aided bainite/martensite steels, quenching and partitioning steels, nanostructured bainite steels, medium manganese steels, etc., are receiving a great deal of attention from both academic and industry sectors, due to their excellent mechanical properties. To apply ferrous steels to a wide range of components and parts, a detailed understanding of the performance of the mechanical properties, such as toughness, fatigue strength, delayed fracture strength, wear property, etc., after heat-treatment, thermo-mechanical process, plastic working (including hot-stamping, hot-forging), welding, surface treatment, etc., will be of great help to steel engineers in future.

For this Special Issue, we are inviting papers on the performance of the mechanical properties of advanced ultra-high-strength ferrous steels subjected to heat-treatment, plastic working, welding, surface treatment, etc. We also welcome novel research on conventional ultra-high-strength ferrous steels containing metastable retained or reverted austenite due to their current significant growth.

Prof. Koh-ichi Sugimoto
Guest Editor

Manuscript Submission Information

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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.

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Keywords

  • Advanced ultrahigh-strength steels
  • Strain-induced transformation
  • Microstructure
  • Mechanical property
  • Heat treatment
  • Thermomechanical process
  • Stamping
  • Forging
  • Welding
  • Surface treatment
  • Applications

Published Papers (6 papers)

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Research

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Open AccessArticle
Influence of the Quenching and Partitioning Process on the Transformation Kinetics and Hardness in a Lean Medium Manganese TRIP Steel
Metals 2019, 9(3), 353; https://doi.org/10.3390/met9030353
Received: 27 February 2019 / Revised: 15 March 2019 / Accepted: 16 March 2019 / Published: 19 March 2019
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Abstract
The quenching and partitioning (Q&P) process of lean medium Mn steels is a novel approach for producing ultra-high strength and good formable steels. First, the steel is fully austenitized, followed by quenching to a specific quenching temperature (TQ) in order [...] Read more.
The quenching and partitioning (Q&P) process of lean medium Mn steels is a novel approach for producing ultra-high strength and good formable steels. First, the steel is fully austenitized, followed by quenching to a specific quenching temperature (TQ) in order to adjust an appropriate amount of initial martensite (α’initial). Subsequently, the steel is reheated to a partitioning temperature (TP) in order to ensure C-partitioning from α’initial to remaining austenite (γremain) and thus retained austenite (RA) stabilization. After isothermal holding, the steel is quenched to room temperature (RT), in order to achieve a martensitic-austenitic microstructure, where the meta-stable RA undergoes the strain-induced martensitic transformation by the so-called transformation induced plasticity (TRIP) effect. This paper systematically investigates the influence of the Q&P process on the isothermal bainitic transformation (IBT) kinetics in a 0.2C-4.5Mn-1.3Al lean medium Mn steel by means of dilatometry. Therefore, the Q&P annealing approach was precisely compared to the TRIP-aided bainitic ferrite (TBF) process, where the samples were directly quenched to the temperature of the IBT after full austenitization. The results indicated an accelerated IBT for the Q&P samples, caused by the formation of α’initial during quenching below the martensite start (MS) temperature. Furthermore, a significant influence of the annealing parameters, such as TQ and TP, was observed with regard to the transformation behavior. For further characterization, light optical microscopy (LOM) and scanning electron microscopy (SEM) were applied, showing a microstructure consisting of a martensitic-bainitic matrix with finely distributed RA islands. Saturation magnetization method (SMM) was used to determine the amount of RA, which was primarily depending on TQ. Furthermore, the hardness according to Vickers revealed a remarkable impact of the annealing parameters, such as TQ and TP, on the predicted mechanical properties. Full article
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Open AccessArticle
Effect of Deformation Temperature on the Portevin-Le Chatelier Effect in Medium-Mn Steel
Received: 24 November 2018 / Revised: 17 December 2018 / Accepted: 18 December 2018 / Published: 20 December 2018
Cited by 1 | PDF Full-text (4715 KB) | HTML Full-text | XML Full-text
Abstract
Experimental investigations of the plastic instability phenomenon in a hot-rolled medium manganese steel were performed. The effects of tensile deformation in a temperature range of 20–140°C on the microstructure, mechanical properties, and flow stress serrations were analyzed. The Portevin–Le Chatelier (PLC) phenomenon was [...] Read more.
Experimental investigations of the plastic instability phenomenon in a hot-rolled medium manganese steel were performed. The effects of tensile deformation in a temperature range of 20–140°C on the microstructure, mechanical properties, and flow stress serrations were analyzed. The Portevin–Le Chatelier (PLC) phenomenon was observed for the specimens deformed at 60 °C, 100 °C, and 140 °C. It was found that the deformation temperature substantially affects the type and intensity of serrations. The type of serration was changed at different deformation temperatures. The phenomenon was not observed at room temperature. The plastic instability occurring for the steel deformed at 60 °C was detected for lower strain levels than for the specimens deformed at 100 °C and 140 °C. The increase of the deformation temperature to 100 °C and 140 °C results in shifting the PLC effect to a post uniform deformation range. The complex issues related to the interaction of work hardening, the transformation induced plasticity (TRIP) effect, and the PLC effect stimulated by the deformation temperature were addressed. Full article
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Open AccessArticle
Evolution of Microstructure and Hardness of High Carbon Steel under Different Compressive Strain Rates
Metals 2018, 8(8), 580; https://doi.org/10.3390/met8080580
Received: 20 June 2018 / Revised: 23 July 2018 / Accepted: 24 July 2018 / Published: 26 July 2018
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Abstract
Understanding the effect of high strain rate deformation on microstructure and mechanical property of metal is important for addressing its performance as high strength material. Strongly motivated by the vast industrial application potential of metals having excellent hardness, we explored the phase stability, [...] Read more.
Understanding the effect of high strain rate deformation on microstructure and mechanical property of metal is important for addressing its performance as high strength material. Strongly motivated by the vast industrial application potential of metals having excellent hardness, we explored the phase stability, microstructure and mechanical performance of an industrial grade high carbon steel under different compressive strain rates. Although low alloyed high carbon steel is well known for their high hardness, unfortunately, their deformation behavior, performance and microstructural evolution under different compressive strain rates are not well understood. For the first time, our investigation revealed that different strain rates transform the metastable austenite into martensite at different volume, simultaneously activate multiple micromechanisms, i.e., dislocation defects, nanotwining, etc. that enhanced the phase stability and refined the microstructure, which is the key for the observed leap in hardness. The combination of phase transformation, grain refinement, increased dislocation density, formation of nanotwin and strain hardening led to an increase in the hardness of high carbon steel. Full article
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Open AccessArticle
Effect of Deformation Temperature on Mechanical Properties and Deformation Mechanisms of Cold-Rolled Low C High Mn TRIP/TWIP Steel
Metals 2018, 8(7), 476; https://doi.org/10.3390/met8070476
Received: 22 May 2018 / Revised: 19 June 2018 / Accepted: 20 June 2018 / Published: 22 June 2018
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Abstract
The microstructure and mechanical properties of cold-rolled Fe-18Mn-3Al-3Si-0.03C transformation induced plasticity/twinning induced plasticity (TRIP/TWIP) steel in the temperature range of 25 to 600 °C were studied. The experimental steel exhibited a good combination of ultimate tensile strength (UTS) of 905 MPa and total [...] Read more.
The microstructure and mechanical properties of cold-rolled Fe-18Mn-3Al-3Si-0.03C transformation induced plasticity/twinning induced plasticity (TRIP/TWIP) steel in the temperature range of 25 to 600 °C were studied. The experimental steel exhibited a good combination of ultimate tensile strength (UTS) of 905 MPa and total elongation (TEL) of 55% at room temperature. With the increase of deformation temperature from 25 to 600 °C, the stacking fault energy (SFE) of the experimental steel increased from 14.5 to 98.8 mJm−2. The deformation mechanism of the experimental steel is controlled by both the strain induced martensite formation and strain induced deformation twinning at 25 °C. With the increase of deformation temperature from 25 to 600 °C, TRIP and TWIP effect were inhibited, and dislocation glide gradually became the main deformation mechanism. The UTS decreased monotonously from 905 to 325 MPa and the TEL decreased (from 55 to 36%, 25–400 °C) and then increased (from 36 to 64%, 400–600 °C). The change in mechanical properties is related to the thermal softening effect, TRIP effect, TWIP effect, DSA, and dislocation slip. Full article
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Open AccessArticle
The Impact of Strain Heterogeneity and Transformation of Metastable Austenite on Springback Behavior in Quenching and Partitioning Steel
Metals 2018, 8(6), 432; https://doi.org/10.3390/met8060432
Received: 3 May 2018 / Revised: 29 May 2018 / Accepted: 5 June 2018 / Published: 7 June 2018
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Abstract
Multiple strengthening methods, such as high dislocation density, high twin density, small grain size, and metastable austenite phase can give high strength to ultra-high strength steels (UHSSs). However, the high strength of UHSSs often results in a greater tendency for springback when applied [...] Read more.
Multiple strengthening methods, such as high dislocation density, high twin density, small grain size, and metastable austenite phase can give high strength to ultra-high strength steels (UHSSs). However, the high strength of UHSSs often results in a greater tendency for springback when applied in manufacturing vehicle components. In the present study, two types of UHSSs, dual-phase (DP) steel and quenching and partitioning (QP) steel are investigated to study the springback behavior during the bending process. Results indicated that both the strain heterogeneity and the transformation of retained austenite impacted the springback behavior. The springback angle of the DP steel increased with the increase in bending angle, which was caused by the increasing degree of strain heterogeneity. However, the springback angle of the QP steel decreased to a 14.75° when QP specimens were strained at a 104° bending angle due to the inhibiting effect of the phase transformation. This indicated that there was preferential phase transformation in the thickness direction in the retained austenite of the outer and inner zones. The phase transformation caused low strain heterogeneity, which resulted in a lower tendency for springback. The results suggested that QP steel could possess lower springback at a proper bending angle. Full article
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Review

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Open AccessFeature PaperReview
An Overview of Fatigue Strength of Case-Hardening TRIP-Aided Martensitic Steels
Metals 2018, 8(5), 355; https://doi.org/10.3390/met8050355
Received: 19 April 2018 / Revised: 3 May 2018 / Accepted: 5 May 2018 / Published: 15 May 2018
Cited by 1 | PDF Full-text (10822 KB) | HTML Full-text | XML Full-text
Abstract
Surface-hardened layer characteristics and fatigue strength properties of transformation-induced plasticity-aided martensitic steels subjected to heat-treatment or vacuum carburization followed by fine-particle peening are revealed for automotive applications specially for powertrain parts. The as-heat-treated steels without the case-hardening process possess excellent impact toughness and [...] Read more.
Surface-hardened layer characteristics and fatigue strength properties of transformation-induced plasticity-aided martensitic steels subjected to heat-treatment or vacuum carburization followed by fine-particle peening are revealed for automotive applications specially for powertrain parts. The as-heat-treated steels without the case-hardening process possess excellent impact toughness and fatigue strength. When the steels are subjected to fine-particle peening after heat-treatment, the fatigue limits of smooth and notched specimens increase considerably, accompanied with low notch sensitivity. Vacuum carburization and subsequent fine-particle peening increases further the fatigue strength of the steels, except notch fatigue limit. The increased fatigue limits are principally associated with high Vickers hardness and compressive residual stress just below the surface, resulting from the severe plastic deformation and the strain-induced martensitic transformation of metastable retained austenite, as well as low surface roughness and fatigue crack initiation depth. Full article
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