Reversed Transformation in Iron-Based Alloys

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

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 8455

Special Issue Editors


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Guest Editor
Department of Materials Science & Engineering, National Taiwan University (NTU), Taipei 10617, Taiwan
Interests: materials characterizations: scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrum, atom probe tomography; materials mechanical behaviors; microstructure and defect physics; phase transformation in alloys; empirical methods: thermo-calc or artificial neural network
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Institute for Materials Research, Tohoku University, Sendai, Japan
Interests: phase transformation; thermodynamics; crystallography; nanoclustering; steels; nitriding; three-dimensional atom probe

Special Issue Information

Dear Colleagues,

In many iron-based alloys, microstructure and mechanical behavior are tailored by transformation from austenite (FCC) to product phase, which is called forward transformation. Actually, reversed transformation from product phase (BCC, BCT, or HCP) to austenite has also been regarded as a critical reaction to optimize mechanical properties of iron-based alloys. Many fundamental contributions on principles of diffusional and displacive transformation have been made, especially for dual-phase (DP) steel, stainless steel, and iron-based shape memory alloy (Fe-SMA). Recently, due to the blooming of complex-phase (CP) steel, medium/high-Mn steel, hot stamp steel, new Fe-SMA, and novel iron-based alloys, reversed transformation is attracting much more attention in physical metallurgy.

All our efforts have made reversed transformation a great leap in recent decay. Austenite reversion, which can occur via diffusional transformation or displacive transformation, is applied to control mechanical properties in DP/CP steel, medium/high-Mn steel, Q&P steel, and hot-stamp steel. Especially, the size and chemical composition of reversed austenite will determine the stability and plastic mechanisms of retained austenite, making strong but ductile steels. Shape memory effect (SME) or super elasticity (SE) occur via HCP-to-FCC displacive transformation in Fe-SMA. Recently, it was found that Fe-28Ni-17Co-11.5Al-2.5Ta-0.05B (at.%) exhibiting a superelastic strain of more than 13% is achieved by BCT-to-FCC transformation. Moreover, coupling-reversed transformation with various metallurgical principles such as precipitation, dislocation engineering, or recrystallization is broadening the road toward advanced alloys with novel properties. The aim of this Special Issue is to provide a premier collection of recent research in reversed transformation in iron-based alloys, including phase transformation, mechanical behavior, materials design, modelling and simulation, characterizations, and future challenges.

Prof. Dr. Hung-Wei (Homer) Yen
Prof. Dr. Goro Miyamoto
Guest Editors

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Keywords

  • Reversed transformation
  • Austenite reversion
  • Shape memory effect
  • Super elasticity
  • Transformation-induced plasticity
  • Twinning-induced plasticity
  • Advanced high-strength steels
  • Austenite memory
  • Austenite grain growth
  • Element partitioning

Published Papers (4 papers)

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Research

8 pages, 4409 KiB  
Article
Overcoming Strength-Ductility Trade-Off at Cryogenic Temperature of Low Carbon Low Alloy Steel via Controlling Retained Austenite Stability
by Xuelin Wang, Zhenjia Xie, Chengjia Shang and Gang Han
Metals 2021, 11(1), 157; https://0-doi-org.brum.beds.ac.uk/10.3390/met11010157 - 15 Jan 2021
Viewed by 1681
Abstract
Stress–strain behavior of a low carbon low alloy multiphase steel with ferrite, tempered bainite, and retained austenite was studied at different cryogenic temperatures. Results indicated that both strength and ductility were enhanced with decreasing tensile testing temperature. The enhancement of both strength and [...] Read more.
Stress–strain behavior of a low carbon low alloy multiphase steel with ferrite, tempered bainite, and retained austenite was studied at different cryogenic temperatures. Results indicated that both strength and ductility were enhanced with decreasing tensile testing temperature. The enhancement of both strength and ductility was attributed to the decreased mechanical stability of retained austenite with decreasing temperature, resulting in sufficient transformation induced plasticity (TRIP) effect for increasing work hardening rate. Full article
(This article belongs to the Special Issue Reversed Transformation in Iron-Based Alloys)
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12 pages, 5461 KiB  
Article
Effect of Starting Microstructures on the Reverse Transformation Kinetics in Low-Carbon Steel
by Junhua Hou and Binbin He
Metals 2020, 10(12), 1601; https://0-doi-org.brum.beds.ac.uk/10.3390/met10121601 - 29 Nov 2020
Cited by 4 | Viewed by 2549
Abstract
The effect of the initial starting microstructures on the austenite reverse transformation kinetics is thoroughly studied in low-carbon steel. The different initial starting microstructures including the ferrite + pearlite, bainite, and martensite are obtained through varied forward transformation. It is found that the [...] Read more.
The effect of the initial starting microstructures on the austenite reverse transformation kinetics is thoroughly studied in low-carbon steel. The different initial starting microstructures including the ferrite + pearlite, bainite, and martensite are obtained through varied forward transformation. It is found that the bainite phase demonstrates highest reverse transformation rate while the ferrite + pearlite shows the lowest transformation rate. The above observation can be explained through the different grain size of the initial starting microstructures as the grain boundaries could act as the nucleation sites for austenite reverse transformation. The explanation is further substantiated based on the consideration of the reverse transformation kinetics from the martensite microstructure with different grain size. Full article
(This article belongs to the Special Issue Reversed Transformation in Iron-Based Alloys)
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9 pages, 8604 KiB  
Article
Enhancing the Robustness and Efficiency in the Production of Medium Mn Steels by Al Addition
by Maokun Bai, Dapeng Yang, Guodong Wang, Joohyun Ryu, Kyooyoung Lee and Hongliang Yi
Metals 2020, 10(11), 1432; https://0-doi-org.brum.beds.ac.uk/10.3390/met10111432 - 28 Oct 2020
Cited by 3 | Viewed by 1320
Abstract
The narrow process window during intercritical annealing and discontinuous yielding have limited the commercialization of medium Mn steels. In this study, a double-annealing process based on the commercial continuous annealing line is proposed. The cold-rolled medium Mn steels were first fully austenitized and [...] Read more.
The narrow process window during intercritical annealing and discontinuous yielding have limited the commercialization of medium Mn steels. In this study, a double-annealing process based on the commercial continuous annealing line is proposed. The cold-rolled medium Mn steels were first fully austenitized and quenched during the first annealing, followed by intercritical annealing for reverted austenite transformation. The microstructure of duplex lath-shaped austenite and ferrite is produced and steel exhibits a desirable continuous yielding during tensile deformation. Al is added into the medium Mn steel to enlarge the process window and to improve the partitioning efficiency of Mn. The produced steel is more robust with temperature fluctuation during the industrial process due to the enlarged intercritical region. Mn partitioning is more efficient owing to the elevated annealing temperature, which results in the improvement of ductility in the Al-added steel with increased austenite stability. Full article
(This article belongs to the Special Issue Reversed Transformation in Iron-Based Alloys)
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11 pages, 4398 KiB  
Article
Transformation-Induced Ductility of Reverse Austenite Evolved by Low-Temperature Tempering of Martensite
by Pengju Du, Peng Chen, Devesh K. Misra, Di Wu and Hongliang Yi
Metals 2020, 10(10), 1343; https://0-doi-org.brum.beds.ac.uk/10.3390/met10101343 - 07 Oct 2020
Cited by 10 | Viewed by 2157
Abstract
A novel steel combining the “quenching and tempering (Q&T)” process was exploited that can achieve the enhancement of austenite by interface migration during tempering the martensitic matrix mixed with films of austenite. A high uniform elongation (12%) combined with high yield tensile strength [...] Read more.
A novel steel combining the “quenching and tempering (Q&T)” process was exploited that can achieve the enhancement of austenite by interface migration during tempering the martensitic matrix mixed with films of austenite. A high uniform elongation (12%) combined with high yield tensile strength (1500 MPa) was obtained, which showed distinct advantages over all the other advanced high strength steels under development for a lightweight car body. Furthermore, the effect of austenite on enhancement of ductility in “Q&T” steels with a martensite matrix was elucidated, which suggested that the ductility was promoted by enhancing boundary sliding and delaying work hardening of the martensitic matrix. Full article
(This article belongs to the Special Issue Reversed Transformation in Iron-Based Alloys)
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