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Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface

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A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Structural Integrity of Metals".

Deadline for manuscript submissions: 31 May 2024 | Viewed by 8355

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Special Issue Editors

Prof. Dr. Francesca Borgioli

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Department of Industrial Engineering (DIEF), Università di Firenze, via di S. Marta 3, 50139 Firenze, Italy
Interests: surface modification of metals and alloys; low-temperature nitriding of stainless steels; oxynitriding of titanium alloys; material characterization
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Dr. Denis Benasciutti

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Department of Engineering, University of Ferrara, via Saragat 1, 44122 Ferrara, Italy
Interests: structural integrity assessment; vibration fatigue; multiaxial fatigue; metal plasticity; finite element analysis
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Prof. Dr. Umberto Prisco

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Department of Chemical, Materials and Production Engineering, University of Napoli Federico II, Piazzale Tecchio, 80, 80125 Napoli, Italy
Interests: mechanical properties; mechanical testing; metal forming; plasticity; processing of materials; additive manufacturing; metal cutting
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Prof. Dr. Tomasz Tański

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Department of Engineering Materials and Biomaterials, Faculty of Mechanical Engineering, Silesian University of Technology, 44-100 Gliwice, Poland
Interests: nanotechnology; thin layers; material properties; structure; heat; surface; plastic treatment
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Special Issue Information

Dear Colleagues,

Metals and alloys continue to play a paramount role in the design and construction of load-bearing structures and mechanical components. Ferrous and non-ferrous alloys find countless applications in various industrial areas, including automotive, aerospace, marine, construction, and manufacturing fields.

When it comes to guarantee the structural integrity and safety of critical parts, a variety of protection and strengthening mechanisms—not only at the bulk level, but also at the surface—may be exploited, not to mention the role of the manufacturing process in establishing the material microstructure and, in turn, its strength. Topics that can be covered are rather broad and may include, but are not limited to, the modification of alloy elements and the formation of new alloys such as high-entropy alloys; heat treatments; advanced manufacturing techniques such as additive manufacturing; and surface engineering techniques such as shot-peening, diffusion treatments, and coatings.

This Special Issue aims to present up-to-date methods and approaches for preserving and improving the structural integrity of metallic components, with a look at phenomena occurring at the bulk and surface level while considering the role of the manufacturing process as it correlates to the microstructure. For this purpose, researchers are invited to submit original articles and review articles illustrating both theoretical and experimental studies.

Prof. Dr. Francesca Borgioli
Dr. Denis Benasciutti
Prof. Dr. Umberto Prisco
Prof. Dr. Tomasz Tański
Guest Editors

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

structural integrity
metal fatigue
alloying
heat treatment
metal manufacturing
additive manufacturing
surface engineering

Published Papers (9 papers)

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Research

Jump to: Review

14 pages, 8934 KiB

Open AccessArticle

Effect of Oxygen on Static Recrystallization Behaviors of Biomedical Ti-Nb-Zr Alloys

by Chan-Byeol Han and Dong-Geun Lee

Metals 2024, 14(3), 333; https://doi.org/10.3390/met14030333 - 14 Mar 2024

Viewed by 636

Abstract

Titanium alloys that are used in biomedical applications must possess biocompatibility and a low elastic modulus so that they protect host bone tissue without causing stress shielding. As the elastic modulus of beta Ti alloys is close to that of bone (10–30 GPa), these alloys are considered potential orthopedic implant materials. The elastic modulus of the single β-phase Ti-39Nb-6Zr (TNZ40) alloy is approximately 40 GPa, whereas the strength is lower than that of other types of Ti alloys. Interstitial oxygen in a Ti matrix is well known to improve the matrix strength by solid-solution hardening. The desired mechanical properties can be optimized using a thermo-mechanical procedure to maintain a low elastic modulus. In order to enhance the strength, TNZ40 alloys were fabricated with different amounts of oxygen. The TNZ-0.16O and TNZ-0.26O alloys were cold swaged into 11 mm diameter bars, subjected to solution treatment at 900 °C and 950 °C for 2 h, and furnace-cooled to room temperature. As a result, recrystallized grains were clearly observed in the β matrix. The TNZ-0.26O alloy that was cold-worked by swaging followed by solution treatment at 900 °C exhibited the best mechanical properties (Vickers hardness: 247 HV, ultimate tensile strength: 777 MPa, elongation at rupture: 18.6%, and compressive strength: 1187 MPa). This study reports the effects of oxygen content on the recrystallization behavior and mechanical properties of these alloys. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)

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12 pages, 7855 KiB

Open AccessArticle

Suppression of Inhomogeneous Plastic Deformation in Medium-Carbon Tempered Martensite Steel

by Hai Qiu, Rintaro Ueji and Tadanobu Inoue

Metals 2024, 14(3), 306; https://doi.org/10.3390/met14030306 - 04 Mar 2024

Viewed by 884

Abstract

The Lüders phenomenon is one type of inhomogeneous plastic deformation occurring in the elastic-to-plastic transition region, and it is an undesirable plastic deformation behavior. Although conventional measures based on the chemical composition design, plasticity processing principle, or utilization of composited microstructures are used to suppress this phenomenon in engineering, demerits are present, such as high cost and low fracture behavior. The Lüders phenomenon begins with the formation of plastic bands (inhomogeneous yielding) at one or several local sites. If yielding simultaneously occurs everywhere rather than at several local sites, the formation of local plastic bands will be inhibited; as a result, the Lüders deformation will be suppressed. Based on this idea, a new approach was proposed in which the number of local yield sites was increased by heat treatments. A medium-carbon tempered martensite steel (Fe-0.3C-1.5Mn, in wt%) was used to verify the validity of the new approach, and the optimum heat-treatment conditions for the balance of mechanical property and deformation behavior were determined. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)

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17 pages, 8510 KiB

Open AccessArticle

Development and Performance Evaluation of a Mechanical Connection for Steel and Shape Memory Alloy Bars

by Min-Kyu Song, Eunsoo Choi and Jong-Han Lee

Metals 2024, 14(3), 300; https://doi.org/10.3390/met14030300 - 02 Mar 2024

Viewed by 699

Abstract

Shape memory alloys (SMAs) demonstrate a shape memory effect and superelasticity that can provide recovery performance to structural members. In this study, a round SMA bar was designed to replace the conventional deformed steel bar, particularly within the plastic hinge section of structural members. To integrate the SMA bar and the existing steel bar, a mechanical coupler was proposed by utilizing the advantages of both one-touch and threaded couplers. Uniaxial tensile tests were conducted to analyze the performance of the proposed coupler and the mechanical properties of the SMA–steel connected bar. Stress and strain relationships were examined for steel bars mechanically connected with the SMA bar and for SMA bars before and after exhibiting the shape memory effect. To induce the shape memory effect, SMA should be heated above the finished austenite temperature. Due to the difficulty of accurately measuring strain on the heated bar using traditional contact methods, we employed digital image correlation technology for precise strain measurement of the heated SMA bar. The experimental results indicate the effective application of SMA bars within the plastic hinge region of structural members using the proposed mechanical coupler. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)

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22 pages, 7995 KiB

Open AccessArticle

Fatigue Reliability Assessment for Orthotropic Steel Decks: Considering Multicrack Coupling Effects

by Jing Liu, Yang Liu, Guodong Wang, Naiwei Lu, Jian Cui and Honghao Wang

Metals 2024, 14(3), 272; https://doi.org/10.3390/met14030272 - 25 Feb 2024

Viewed by 627

Abstract

Multiple fatigue cracks are generally present in practical engineering due to the existence of welding; the size and number of cracks of orthotropic steel bridge decks are greatly uncertain. The component failure conditions caused by these cracks may have correlations. Currently, it is still a challenging issue to develop a physical model of multiple fatigue crack propagation in bridge decks and perform a fatigue reliability assessment, which is also the motivation that drives the innovation of this study. A fatigue reliability evaluation method is presented for orthotropic steel bridge decks, considering the coupling effect of multiple cracks and the randomness of vehicle loading. A numerical simulation method for multifatigue crack growth is developed by combining the ABAQUS and FRANC3D programs. The equivalent crack depth under different spacing and depths of collinear cracks is calculated by using numerical simulation and the multicrack equivalent characterization method. The critical damage accumulation function of multiple fatigue cracks is established using linear elastic fracture mechanics. Subsequently, the critical damage accumulation function of multiple fatigue cracks is established based on linear elastic fracture mechanics. In order to solve the time-consuming problem of traditional Monte Carlo method, the iHL-RF method and AK-MCS method are developed for fatigue reliability analysis. The results show that compared with the single-crack model, the fatigue reliability of orthotropic steel deck will be crucially reduced considering the coupling effect of double cracks. The MCS, iHL-RF and AK-MCS methods can effectively solve the fatigue reliability analysis problem. Compared with the MCS method, the reliability calculation time based on AK-MCS method is significantly reduced. The AK-MCS method-based method reduces the time for calculating the reliability of orthotropic steel decks by 50% compared with the iHL-RF method. The reliability analysis of orthotropic steel deck bridge based on AK-MCS method is proved to be efficient and accurate. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)

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15 pages, 10346 KiB

Open AccessFeature PaperArticle

Synergic Effects of Nanosecond Laser Ablation and PVD-Coating on Cemented Carbides: Assessment on Surface and Mechanical Integrity

by Shiqi Fang, Luis Llanes, Y. B. Guo and Dirk Bähre

Metals 2024, 14(1), 34; https://doi.org/10.3390/met14010034 - 28 Dec 2023

Viewed by 898

Abstract

Emerging laser precision machining, particularly using pulsed lasers, enlightens the innovation and functionalization of cemented carbides. These backbone materials of the tooling industry are usually considered difficult to machine or shape using conventional mechanical approaches. The coating of cemented carbide tools, deemed to improve their mechanical and thermal properties, is a common supplementary surface treatment prior to their application. This work aims to study the synergic effects of nanosecond laser ablation and coating deposition on the surface, as well as the mechanical integrity of cemented carbides. In this regard, two plain WC–Co grades with different metallic binder content (10%_wtCo and 15%_wtCo) were first processed by a short-pulsed nanosecond laser. Subsequently, an AlTiN film was physically vapor-deposited on the laser-processed surfaces. The resulting surface integrity was assessed in terms of topographical, morphological, and microstructural changes. Mechanical integrity was evaluated in terms of indentation and sliding contact responses using Vickers hardness and scratch tests, respectively, the latter including frictional, penetrating, and sliding performances under selected surface processing conditions. In general, the nanosecond laser ablation proved to be beneficial for the mechanical integrity of coated cemented carbides in most studied cases, as it increased surface hardness, reduced penetration depth, and hindered damage during sliding. This was the case despite a slight increase in surface roughness, as well as minor morphological and microstructural changes at the coating–substrate interface, discerned. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)

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17 pages, 31245 KiB

Open AccessArticle

Effect of Nanostructuring on Operational Properties of 316LVM Steel

by Olga Rybalchenko, Natalia Anisimova, Natalia Martynenko, Georgy Rybalchenko, Alexey Tokar, Elena Lukyanova, Dmitry Prosvirnin, Mikhail Gorshenkov, Mikhail Kiselevskiy and Sergey Dobatkin

Metals 2023, 13(12), 1951; https://doi.org/10.3390/met13121951 - 28 Nov 2023

Viewed by 646

Abstract

In this study, high-pressure torsion (HPT) was used to process austenitic 316LVM stainless steel at 20 °C and 400 °C. The effects of HPT on the microstructure, mechanical, and functional properties of the steel were investigated. By applying both HPT modes on the 316LVM steel, a nanocrystalline state with an average size of the structural elements of ~46–50 nm was achieved. The density of the dislocations and twins present in the austenite phase varied depending on the specific HPT conditions. Despite achieving a similar structural state after HPT, the deformation temperatures used has different effects on the mechanical and functional properties of the steel. After HPT at 20 °C, the yield strength of the 316L steel increased by more than nine times up to 1890 MPa, and the fatigue limit by more than two times up to 550 MPa, when compared to its coarse-grained counter-parts. After HPT at 20 °C, the 316LVM steel exhibited better ductility, higher low-cycle fatigue resistance, greater resistance to corrosion, and improved in vitro biocompatibility compared to processing at 400 °C. The reasons for the deterioration of the properties after HPT at 400 °C are discussed in the article. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)

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14 pages, 4559 KiB

Open AccessFeature PaperArticle

Effects of Solid-Solution Carbon and Eutectic Carbides in AISI 316L Steel-Based Tungsten Carbide Composites on Plasma Carburizing and Nitriding

by Shinichiro Adachi, Takuto Yamaguchi, Keigo Tanaka, Takashi Nishimura and Nobuhiro Ueda

Metals 2023, 13(8), 1350; https://doi.org/10.3390/met13081350 - 27 Jul 2023

Cited by 3 | Viewed by 975

Abstract

AISI 316L stainless-steel-based tungsten carbide composite layers fabricated via laser metal deposition are used for additive manufacturing. Heat treatment practices such as low-temperature plasma carburizing and nitriding improve the hardness and corrosion resistance of austenitic stainless steels via the formation of expanded austenite, known as the S phase. In the present study, practices to enhance the hardness and corrosion resistances of the stainless-steel parts in the composite layers have been investigated, including single plasma carburizing for 4 h and continuous plasma nitriding for 3.5 h following carburizing for 0.5 h at 400 and 450 °C. The as-deposited composite layers contain solid-solution carbon and eutectic carbides owing to the thermal decomposition of tungsten carbide during the laser metal deposition. The eutectic carbides inhibit carbon diffusion, whereas the original solid-solution carbon contributes to the formation of the S phase, resulting in a thick S phase layer. Both the single carburizing and continuous processes are effective in improving the Vickers surface hardness and corrosion resistance of the composite layers despite containing the solid-solution carbon and eutectic carbides. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)

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Review

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36 pages, 12230 KiB

Open AccessReview

Fracture Behaviour of Aluminium Alloys under Coastal Environmental Conditions: A Review

by Ibrahim Alqahtani, Andrew Starr and Muhammad Khan

Metals 2024, 14(3), 336; https://doi.org/10.3390/met14030336 - 15 Mar 2024

Viewed by 991

Abstract

Aluminium alloys have been integral to numerous engineering applications due to their favourable strength, weight, and corrosion resistance combination. However, the performance of these alloys in coastal environments is a critical concern, as the interplay between fracture toughness and fatigue crack growth rate under such conditions remains relatively unexplored. This comprehensive review addresses this research gap by analysing the intricate relationship between fatigue crack propagation, fracture toughness, and challenging coastal environmental conditions. In view of the increasing utilisation of aluminium alloys in coastal infrastructure and maritime industries, understanding their behaviour under the joint influences of cyclic loading and corrosive coastal atmospheres is imperative. The primary objective of this review is to synthesise the existing knowledge on the subject, identify research gaps, and propose directions for future investigations. The methodology involves an in-depth examination of peer-reviewed literature and experimental studies. The mechanisms driving fatigue crack initiation and propagation in aluminium alloys exposed to saltwater, humidity, and temperature variations are elucidated. Additionally, this review critically evaluates the impact of coastal conditions on fracture toughness, shedding light on the vulnerability of aluminium alloys to sudden fractures in such environments. The variability of fatigue crack growth rates and fracture toughness values across different aluminium alloy compositions and environmental exposures was discussed. Corrosion–fatigue interactions emerge as a key contributor to accelerated crack propagation, underscoring the need for comprehensive mitigation strategies. This review paper highlights the pressing need to understand the behaviour of aluminium alloys under coastal conditions comprehensively. By revealing the existing research gaps and presenting an integrated overview of the intricate mechanisms at play, this study aims to guide further research and engineering efforts towards enhancing the durability and safety of aluminium alloy components in coastal environments. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)

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23 pages, 8319 KiB

Open AccessFeature PaperReview

Very High Cycle Fatigue of Welds: A Review

by Andrew England, Athanasios Toumpis and Yevgen Gorash

Metals 2023, 13(11), 1860; https://doi.org/10.3390/met13111860 - 07 Nov 2023

Cited by 1 | Viewed by 1358

Abstract

The design life of welded structures and components extends into the very high cycle fatigue (VHCF) regime across various applications. However, the availability of data on the fatigue behaviour of welded joints in the VHCF regime is limited, particularly when compared to the low and high cycle fatigue regimes. The development of ultrasonic fatigue testing equipment has accelerated fatigue testing and allowed for the VHCF properties of welds to be investigated in a feasible timeframe. In the present review, the emerging research concerning the VHCF behaviour of welds of various steels and non-ferrous alloys are individually explored. Overall, it is observed that welded joints have significantly lower fatigue strength than the base metal in the VHCF regime and that welding defects have a considerable influence on fatigue strength. Through the discussion of the relevant literature, important findings concerning the effects of specimen geometry and fatigue improvement methods are underlined. Furthermore, the guidance provided within design standards is compared, and some examples of VHCF failures of in-service components are highlighted. Finally, perspectives on future directions of investigation are put forward with the aim of encouraging further research in the field of VHCF of welds. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)

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