Special Issue "Physical Metallurgy of High Performance Steels"

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

Deadline for manuscript submissions: 31 October 2018

Special Issue Editor

Guest Editor
Prof. Dong-Woo Suh

Graduate Institute of Ferrous Technology (GIFT), Pohang University of Science and Technology (POSTECH), Korea
Website | E-Mail
Interests: phase transformation in ferrous alloys; alloy design and microstructure control for advanced high strength steel; degradation of ferrous alloys in non-friendly environment

Special Issue Information

Dear Colleagues,

Ever since human being started using alloys of iron, steels always have served as a backbone material for our society. It is possible because of endless evolution, making them exceptionally responsive to changes in social environments. Physical metallurgy primarily concerns the microstructure and mechanical properties of materials with their relationships. In this context, it is an essential subject for the persistent evolution of alloys of iron, creating a variety of novel high-performance steels. Recently, getting into more intensive competition with other structural alternatives, such as light metals or plastics, alloys of iron are required to make another quantum leap. This Special Issue attempts to compile efforts in the latest advances in the development of high-performance steels, particularly putting emphasis on fundamental and practical issues in physical metallurgy. Contributions are expected to navigate the everlasting evolution of steels in the future.

Prof. Dr. Dong-Woo Suh
Guest Editor

Manuscript Submission Information

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Keywords

  • Steels

  • Microstructure

  • Mechanical behavior

  • Alloy design

  • Thermo-mechanical process

  • Phase transformation

Published Papers (5 papers)

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Research

Open AccessArticle The Effect of Gadolinium on the Microstructures and Charpy Impact Properties of Super Duplex Stainless Steels
Metals 2018, 8(7), 474; https://doi.org/10.3390/met8070474
Received: 21 May 2018 / Revised: 10 June 2018 / Accepted: 19 June 2018 / Published: 21 June 2018
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Abstract
Super duplex stainless steels (SDSSs), exhibiting excellent strength and corrosion resistance, serve as the attractive materials in a variety of industries. However, improvements in their ductility and impact-toughness are required in extreme environments. In this study, the effects of gadolinium on the microstructures
[...] Read more.
Super duplex stainless steels (SDSSs), exhibiting excellent strength and corrosion resistance, serve as the attractive materials in a variety of industries. However, improvements in their ductility and impact-toughness are required in extreme environments. In this study, the effects of gadolinium on the microstructures and Charpy impact properties of super duplex stainless steels were investigated. A base super duplex stainless steel (BDSS) and a gadolinium-added super duplex stainless steel (GDSS) were successfully fabricated using an air casting method. The oxygen content and grain size of SDSSs were found to decrease because of high reactivity of gadolinium with oxygen. Moreover, the average inclusion size and area of GDSS also decreased even with a slight decrease in the average distance between inclusions. Both the BDSS and GDSS exhibited typical Charpy impact transition behavior from −196 °C to 200 °C. Moreover, the GDSS impact energies using Charpy test were higher than those of BDSS over the entire temperature range. Moreover, the ductile-to-brittle transition temperature (DBTT) of SDSSs calculated from the fracture appearance transition temperature (FATT) significantly decreased by over 20 °C with the addition of gadolinium. Full article
(This article belongs to the Special Issue Physical Metallurgy of High Performance Steels)
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Open AccessArticle Hardening Embrittlement and Non-Hardening Embrittlement of Welding-Heat-Affected Zones in a Cr-Mo Low Alloy Steel
Metals 2018, 8(6), 405; https://doi.org/10.3390/met8060405
Received: 8 May 2018 / Revised: 23 May 2018 / Accepted: 27 May 2018 / Published: 1 June 2018
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Abstract
The embrittlement of heat affected zones (HAZs) resulting from the welding of a P-doped 2.25Cr-1Mo steel was studied by the analysis of the fracture appearance transition temperatures (FATTs) of the HAZs simulated under a heat input of 45 kJ/cm with different peak temperatures.
[...] Read more.
The embrittlement of heat affected zones (HAZs) resulting from the welding of a P-doped 2.25Cr-1Mo steel was studied by the analysis of the fracture appearance transition temperatures (FATTs) of the HAZs simulated under a heat input of 45 kJ/cm with different peak temperatures. The FATTs of the HAZs both with and without tempering increased with the rise of the peak temperature. However, the FATTs were apparently lower for the tempered HAZs. For the as-welded (untempered) HAZs, the FATTs were mainly affected by residual stress, martensite/austenite (M/A) islands, and bainite morphology. The observed embrittlement is a hardening embrittlement. On the other hand, the FATTs of the tempered HAZs were mainly affected by phosphorus grain boundary segregation, thereby causing a non-hardening embrittlement. The results demonstrate that the hardening embrittlement of the as-welded HAZs was more severe than the non-hardening embrittlement of the tempered HAZs. Consequently, a post-weld heat treatment should be carried out if possible so as to eliminate the hardening embrittlement. Full article
(This article belongs to the Special Issue Physical Metallurgy of High Performance Steels)
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Open AccessArticle Strain Hardening Behavior and Microstructure Evolution of High-Manganese Steel Subjected to Interrupted Tensile Tests
Metals 2018, 8(2), 122; https://doi.org/10.3390/met8020122
Received: 18 January 2018 / Revised: 5 February 2018 / Accepted: 7 February 2018 / Published: 10 February 2018
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Abstract
Strain hardening behavior and the corresponding microstructure evolution of the high-manganese steel with additions of Si and Al were investigated in this study. Thermomechanically processed and solution-heat-treated sheet steels were compared under conditions of interrupted tensile tests. Relationships between microstructure and strain hardening
[...] Read more.
Strain hardening behavior and the corresponding microstructure evolution of the high-manganese steel with additions of Si and Al were investigated in this study. Thermomechanically processed and solution-heat-treated sheet steels were compared under conditions of interrupted tensile tests. Relationships between microstructure and strain hardening were assessed for different strain levels using light microscopy and scanning electron microscopy techniques. It was found that the deformation of both steels at low strain levels was dominated by dislocation glide before the occurrence of mechanical twinning. The amount of twins, slip lines, and bands was increasing gradually up to the point of necking. As the strain level increased, dislocation density within twinning areas becomes higher, which enhances the strength, the work hardening exponent, and the work hardening rate of the investigated high-manganese sheet steels. Full article
(This article belongs to the Special Issue Physical Metallurgy of High Performance Steels)
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Open AccessArticle Microstructural, Mechanical, and Electrochemical Analysis of Duplex and Superduplex Stainless Steels Welded with the Autogenous TIG Process Using Different Heat Input
Metals 2017, 7(12), 538; https://doi.org/10.3390/met7120538
Received: 1 November 2017 / Revised: 23 November 2017 / Accepted: 27 November 2017 / Published: 1 December 2017
Cited by 2 | PDF Full-text (16967 KB) | HTML Full-text | XML Full-text
Abstract
Duplex Stainless Steels (DSS) and Superduplex Stainless Steels (SDSS) have a strong appeal in the petrochemical industry. These steels have excellent properties, such as corrosion resistance and good toughness besides good weldability. Welding techniques take into account the loss of alloying elements during
[...] Read more.
Duplex Stainless Steels (DSS) and Superduplex Stainless Steels (SDSS) have a strong appeal in the petrochemical industry. These steels have excellent properties, such as corrosion resistance and good toughness besides good weldability. Welding techniques take into account the loss of alloying elements during the process, so this loss is usually compensated by the addition of a filler metal rich in alloying elements. A possible problem would be during the welding of these materials in adverse conditions in service, where the operator could have difficulties in welding with the filler metal. Therefore, in this work, two DSS and one SDSS were welded, by autogenous Tungsten Inert Gas (TIG), i.e., without addition of a filler metal, by three different heat inputs. After welding, microstructural, mechanical, and electrochemical analysis was performed. The microstructures were characterized for each welding condition, with the aid of optical microscopy (OM). Vickers hardness, Charpy-V, and cyclic polarization tests were also performed. After the electrochemical tests, the samples were analyzed by scanning electron microscopy (SEM). The SDSS welded with high heat input kept the balance of the austenite and ferrite, and toughness above the limit value. The hardness values remain constant in the weld regions and SDSS is the most resistant to corrosion. Full article
(This article belongs to the Special Issue Physical Metallurgy of High Performance Steels)
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Graphical abstract

Open AccessArticle Effect of Grain Size on Grain Boundary Segregation Thermodynamics of Phosphorus in Interstitial-Free and 2.25Cr-1Mo Steels
Metals 2017, 7(11), 470; https://doi.org/10.3390/met7110470
Received: 27 September 2017 / Revised: 23 October 2017 / Accepted: 31 October 2017 / Published: 2 November 2017
Cited by 2 | PDF Full-text (4562 KB) | HTML Full-text | XML Full-text
Abstract
Several grain sizes were obtained by heat treatment at different temperatures for interstitial-free (IF) and 2.25Cr-1Mo steels. Samples of the steels with different grain sizes were aged at 600 and 680 °C for IF steel and 520 and 560 °C for 2.25Cr-1Mo steel
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Several grain sizes were obtained by heat treatment at different temperatures for interstitial-free (IF) and 2.25Cr-1Mo steels. Samples of the steels with different grain sizes were aged at 600 and 680 °C for IF steel and 520 and 560 °C for 2.25Cr-1Mo steel for sufficient time to achieve their equilibrium grain boundary segregation. The grain boundary concentrations of phosphorus were examined using Auger electron spectroscopy. At the same aging temperature, the boundary segregation of phosphorus increased with increasing grain size. The effect of grain size on equilibrium grain boundary segregation thermodynamics was analyzed based on the information of both grain size and phosphorus boundary concentration. The segregation enthalpy increased with increasing grain size and simultaneously the segregation entropy became less negative. Moreover, the segregation entropy (∆S) and enthalpy (∆H) of phosphorus in both IF and 2.25Cr-1Mo steels exhibited a unified linear relationship, being expressed as ∆S = 0.85∆H − 38.06, although it segregated to different types of grain boundaries (ferrite grain boundaries in IF steel and prior austenite grain boundaries in 2.25Cr-1Mo steel). With the aid of the acquired thermodynamic parameters and grain boundary segregation theories, the equilibrium segregation concentrations at different aging temperatures were modeled under different grain sizes for both steels. Full article
(This article belongs to the Special Issue Physical Metallurgy of High Performance Steels)
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