Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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13 pages, 9623 KiB  
Article
Effect of Tropical Marine Atmospheric Environment on Corrosion Behaviour of the 7B04-T74 Aluminium Alloy
by Ning Li, Weifang Zhang, Xiaojun Yan, Meng Zhang, Lu Han and Yikun Cai
Metals 2023, 13(5), 995; https://doi.org/10.3390/met13050995 - 21 May 2023
Cited by 2 | Viewed by 1683
Abstract
In this work, the effects of the tropical marine atmospheric environment on the corrosion behaviour of the 7B04-T74 aluminium alloy were systematically investigated by using accelerated testing, together with corrosion kinetic analysis, microstructure observation, product composition analysis, and potentiodynamic polarization curve tests. The [...] Read more.
In this work, the effects of the tropical marine atmospheric environment on the corrosion behaviour of the 7B04-T74 aluminium alloy were systematically investigated by using accelerated testing, together with corrosion kinetic analysis, microstructure observation, product composition analysis, and potentiodynamic polarization curve tests. The weight loss method was used for the corrosion kinetics analysis. The surface morphology and corrosion products transformation law were investigated by OM, SEM, EDS, and XPS. The electrochemical characteristics were studied using potentiodynamic polarization curves. The research indicated that the 7B04-T74 aluminium alloy has eminent corrosion resistance in the tropical marine atmospheric environment. Localized pitting corrosion occurred rapidly in the tropical marine atmosphere. In the later stage of corrosion, the corrosion of aluminium alloy did not become serious. Specifically, no obvious intergranular corrosion was found, which is related to the thermal treatment method. Corrosion products included Al(OH)3, Al2O3, and AlCl3, of which Al(OH)3 is the most notable. Full article
(This article belongs to the Special Issue Corrosion Prediction in Different Environment)
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11 pages, 1840 KiB  
Article
Corrosion of Copper in a Tropical Marine Atmosphere Rich in H2S Resulting from the Decomposition of Sargassum Algae
by Mahado Said Ahmed, Mounim Lebrini, Benoit Lescop, Julien Pellé, Stéphane Rioual, Olivia Amintas, Carole Boullanger and Christophe Roos
Metals 2023, 13(5), 982; https://doi.org/10.3390/met13050982 - 19 May 2023
Cited by 3 | Viewed by 1764
Abstract
The atmospheric corrosion of copper exposed in Martinique (Caribbean Sea) for 1 year was reported. This island suffered the stranding of sargassum algae, which decompose and release toxic gases such as hydrogen sulfide (H2S) or ammonia (NH3). Four sites [...] Read more.
The atmospheric corrosion of copper exposed in Martinique (Caribbean Sea) for 1 year was reported. This island suffered the stranding of sargassum algae, which decompose and release toxic gases such as hydrogen sulfide (H2S) or ammonia (NH3). Four sites in Martinique (France) more or less impacted by sargassum algae strandings were selected. The corrosion rate was studied via mass loss determination. The morphology and properties of the corrosion products were determined using Scanning Electron Microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The samples were exposed for up to 12 months. The mass loss results after 1-year exposure were from 4.8 µm for the least impacted site to 325 µm for the site most affected by sargassum algae. This very high value proves that the presence of sargassum algae caused a significant degradation of copper. The morphological structures and properties of the corrosion products obtained at the impacted and non-impacted sites differed significantly. In the absence of sargassum algae, classical corrosion products of copper were reported such as Cu2O and Cu2Cl(OH)3. In the sites near the stranding of the sargassum algae, the CuS product is the main corrosion product obtained, but copper hydroxylsulfate is created. Full article
(This article belongs to the Section Corrosion and Protection)
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13 pages, 80879 KiB  
Article
Corrosion Behavior of the AZ31 Mg Alloy in Neutral Aqueous Solutions Containing Various Anions
by Duyoung Kwon, Hien Van Pham, Pungkeun Song and Sungmo Moon
Metals 2023, 13(5), 962; https://doi.org/10.3390/met13050962 - 16 May 2023
Cited by 1 | Viewed by 1449
Abstract
This work demonstrates the corrosion behavior of the AZ31 Mg alloy as a function of an immersion time of 48 h in 0.1 M HCl, H2SO4, H3PO4 and HF solutions, in which pH was adjusted to [...] Read more.
This work demonstrates the corrosion behavior of the AZ31 Mg alloy as a function of an immersion time of 48 h in 0.1 M HCl, H2SO4, H3PO4 and HF solutions, in which pH was adjusted to 6 to exclude the contribution of hydrogen ions (H+) and hydroxide ions (OH). In situ observations, open circuit potential (OCP), weight changes and AC impedance measurements were performed with an immersion time of 48 h and the morphologies and chemical compositions of the surface products after 48 h of immersion were analyzed by SEM, EDS and XPS. In the chloride ion (Cl)-containing solution, the corrosion of the AZ31 Mg alloy initiated locally and propagated discontinuously over the surface with immersion time. The OCP value of the AZ31 Mg alloy showed an initial increase from −1.51 VAg/AgCl to −1.47 VAg/AgCl after about 5 h of immersion and then a decrease to −1.51 VAg/AgCl due to corrosion initiation. In the F-containing solution, after 48 h of immersion, the OCP showed an extremely large value of −0.6 VAg/AgCl, while the relatively lower values of −1.52 VAg/AgCl, −1.59 VAg/AgCl were seen in the solutions containing SO42− and PO43, respectively. In the sulfate ion (SO42−)-containing neutral aqueous solution, needle-like surface films were formed and there were no changes in the weight of the AZ31 Mg alloy with immersion time. In the phosphate ion (PO43−)-containing neutral aqueous solution, a vigorous gas evolution occurred, together with the formation of black surface films with cracks, and a high corrosion rate of −13.8018 × 10−3 g·cm−2·day−1 was obtained. In the fluoride ion (F)-containing neutral aqueous solution, a surface film with crystalline grains of MgF2 was formed and the weight of the AZ31 Mg alloy increased continuously with immersion time. In conclusion, the corrosion of the AZ31 Mg alloy occurred uniformly in neutral phosphate solution but locally in chloride solution. No corrosion was observed in either the neutral sulfate or fluoride solutions. Full article
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14 pages, 4704 KiB  
Article
Electrochemical Corrosion Behavior of 310S Stainless Steel in Hot Concentrated Tap Water
by Wen Xian, Zhong Yin, Lele Liu and Moucheng Li
Metals 2023, 13(4), 713; https://doi.org/10.3390/met13040713 - 05 Apr 2023
Cited by 2 | Viewed by 1216
Abstract
The corrosion behavior of 310S stainless steel was investigated in synthetic tap water and Ca2+ and Mg2+-free solutions with different concentration ratios at 80 °C using electrochemical measurement techniques and surface analysis methods. The main purpose was to obtain the [...] Read more.
The corrosion behavior of 310S stainless steel was investigated in synthetic tap water and Ca2+ and Mg2+-free solutions with different concentration ratios at 80 °C using electrochemical measurement techniques and surface analysis methods. The main purpose was to obtain the electrochemical corrosion characteristics under carbonate scale conditions. The specimens displayed a spontaneous passivation state in the solutions with or without Ca2+ and Mg2+ ions. With the enlargement of the concentration ratio of synthetic tap water from 1 to 10 times, the polarization resistance under free corrosion conditions and the pitting potential decreased by about 48% and 327 mV, respectively. The pitting tendency increased with increasing concentration ratio of tap water. The carbonate scales deposited from the synthetic tap water solutions were mainly composed of CaCO3, which led to a slight increase in the polarization resistance and the pitting potential and decrease in the passive current density. Full article
(This article belongs to the Special Issue Applications of Electrochemistry in Corrosion Science and in Practice)
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38 pages, 7189 KiB  
Review
High-Entropy Alloy Coatings Deposited by Thermal Spraying: A Review of Strengthening Mechanisms, Performance Assessments and Perspectives on Future Applications
by Rakesh Bhaskaran Nair, Raunak Supekar, Seyyed Morteza Javid, Wandong Wang, Yu Zou, André McDonald, Javad Mostaghimi and Pantcho Stoyanov
Metals 2023, 13(3), 579; https://doi.org/10.3390/met13030579 - 13 Mar 2023
Cited by 12 | Viewed by 3966
Abstract
Thermal spray deposition techniques have been well-established, owing to their flexibility in addressing degradation due to wear and corrosion issues faced due to extreme environmental conditions. With the adoption of these techniques, a broad spectrum of industries is experiencing continuous improvement in resolving [...] Read more.
Thermal spray deposition techniques have been well-established, owing to their flexibility in addressing degradation due to wear and corrosion issues faced due to extreme environmental conditions. With the adoption of these techniques, a broad spectrum of industries is experiencing continuous improvement in resolving these issues. To increase industrial-level implementation, state-of-the-art advanced materials are required. High-entropy alloys (HEAs) have recently gained considerable attention within the scientific community as advanced materials, mainly due to their exceptional properties and desirable microstructural features. Unlike traditional material systems, high-entropy alloys are composed of multi-component elements (at least five elements) with equimolar or nearly equimolar concentrations. This allows for a stable microstructure that is associated with high configurational entropy. This review article provides a critical assessment of different strengthening mechanisms observed in various high-entropy alloys developed by means of deposition techniques. The wear, corrosion, and oxidation responses of these alloys are reviewed in detail and correlated to microstructural and mechanical properties and behavior. In addition, the review focused on material design principles for developing next-generation HEAs that can significantly benefit the aerospace, marine, oil and gas, nuclear sector, etc. Despite having shown exceptional mechanical properties, the article describes the need to further evaluate the tribological behavior of these HEAs in order to show proof-of-concept perspectives for several industrial applications in extreme environments. Full article
(This article belongs to the Special Issue Wear and Corrosion Behavior of High-Entropy Alloy)
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17 pages, 5148 KiB  
Article
Stress Corrosion Cracking Mechanisms of UNS S32205 Duplex Stainless Steel in Carbonated Solution Induced by Chlorides
by Ulises Martin and David M. Bastidas
Metals 2023, 13(3), 567; https://doi.org/10.3390/met13030567 - 11 Mar 2023
Cited by 4 | Viewed by 3308
Abstract
Herein, the chloride-induced stress corrosion cracking (SCC) mechanisms of UNS S32205 duplex stainless steel (DSS) reinforcing bars in alkaline and carbonated solutions are studied. Electrochemical monitoring and mechanical properties were tested using linear polarization resistance and electrochemical impedance spectroscopy, coupled with the slow [...] Read more.
Herein, the chloride-induced stress corrosion cracking (SCC) mechanisms of UNS S32205 duplex stainless steel (DSS) reinforcing bars in alkaline and carbonated solutions are studied. Electrochemical monitoring and mechanical properties were tested using linear polarization resistance and electrochemical impedance spectroscopy, coupled with the slow strain rate tensile test (SSRT) to evaluate the SCC behavior and unravel the pit-to-crack mechanisms. Pit initiation and crack morphology were identified by fractographic analysis, which revealed the transgranular (TG) SCC mechanism. HCO3 acidification enhanced the anodic dissolution kinetics, thus promoting a premature pit-to-crack transition, seen by the decrease in the maximum phase angle in the Bode plot at low frequencies (≈ 1 Hz) for the carbonated solution. The crack propagation rate for the carbonated solution increased by over 100% compared to the alkaline solution, coinciding with the lower phase angle from the Bode plots, as well as with the lower charge transfer resistance. Pit initiation was found at the TiN nonmetallic inclusion inside the ferrite phase cleavage facet, which developed TG-SCC. Full article
(This article belongs to the Special Issue Corrosion and Protection of Stainless Steels)
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21 pages, 14270 KiB  
Article
Effect of Laser Shock Peening on the Stress Corrosion Cracking of 304L Stainless Steel
by Young-Ran Yoo, Seung-Heon Choi and Young-Sik Kim
Metals 2023, 13(3), 516; https://doi.org/10.3390/met13030516 - 03 Mar 2023
Cited by 6 | Viewed by 1905
Abstract
Storage canisters used in nuclear power plants operating in seaside areas—where the salt content in the atmosphere is high—may be susceptible to chloride-induced stress corrosion cracking (CISCC). Chloride-induced stress corrosion cracking is one of the ways in which dry storage canisters made of [...] Read more.
Storage canisters used in nuclear power plants operating in seaside areas—where the salt content in the atmosphere is high—may be susceptible to chloride-induced stress corrosion cracking (CISCC). Chloride-induced stress corrosion cracking is one of the ways in which dry storage canisters made of stainless steel can degrade. Stress corrosion cracking depends on the microstructure and residual stress, and it is therefore very important to improve the surface properties of materials. Laser shock peening both greatly deforms the material surface and refines grains, and it generates compressive residual stress in the deep part from the surface of the material. This study focused on the effect of laser shock peening on the stress corrosion cracking of 304L stainless steel. The laser shock peening was found to induce compressive residual stress from the surface to a 1 mm depth, and the SCC properties were evaluated by a U-bend test. The results showed that the SCC resistance of laser-peened 304L stainless steel in a chloride environment was enhanced, and that it was closely related to grain size, the pitting potential of the cross section, and residual stress. Full article
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29 pages, 15823 KiB  
Review
Corrosion Behavior of High Entropy Alloys and Their Application in the Nuclear Industry—An Overview
by Tianrun Li, Debin Wang, Suode Zhang and Jianqiang Wang
Metals 2023, 13(2), 363; https://doi.org/10.3390/met13020363 - 10 Feb 2023
Cited by 9 | Viewed by 2457
Abstract
With multiple principal components, high entropy alloys (HEAs) have aroused great interest due to their unique microstructures and outstanding properties. Recently, the corrosion behavior of HEAs has become a scientific hotspot in the area of material science and engineering, and HEAs can exhibit [...] Read more.
With multiple principal components, high entropy alloys (HEAs) have aroused great interest due to their unique microstructures and outstanding properties. Recently, the corrosion behavior of HEAs has become a scientific hotspot in the area of material science and engineering, and HEAs can exhibit good protection against corrosive environments. A comprehensive understanding of the corrosion mechanism of HEAs is important for further design of HEAs with better performance. This paper reviews the corrosion properties and mechanisms of HEAs (mainly Cantor alloy and its variants) in various environments. More crucially, this paper is focused on the influences of composition and microstructure on the evolution of the corrosion process, especially passive film stability and localized corrosion resistance. The corrosion behavior of HEAs as structural materials in nuclear industry applications is emphasized. Finally, based on this review, the possible perspectives for scientific research and engineering applications of HEAs are proposed. Full article
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13 pages, 13119 KiB  
Article
Effect of Superhydrophobic Surface on Corrosion Resistance of Magnesium-Neodymium Alloy in Artificial Hand Sweat
by Changyang Liu, Jiapeng Sun and Guosong Wu
Metals 2023, 13(2), 219; https://doi.org/10.3390/met13020219 - 24 Jan 2023
Cited by 3 | Viewed by 1362
Abstract
A superhydrophobic surface can endow metals with some intriguing characteristics such as self-cleaning behavior. In this study, a simple solution-immersion method based on the concept of predesigned corrosion is developed to enhance the corrosion resistance of a magnesium-neodymium alloy. The Mg alloy is [...] Read more.
A superhydrophobic surface can endow metals with some intriguing characteristics such as self-cleaning behavior. In this study, a simple solution-immersion method based on the concept of predesigned corrosion is developed to enhance the corrosion resistance of a magnesium-neodymium alloy. The Mg alloy is directly soaked in potassium dihydrogen phosphate solution with the addition of ultrasound, and a layer of rough but dense coating is uniformly formed on the Mg-Nd alloy after the immersion process, which is mainly composed of MgHPO4∙3H2O. A superhydrophobic surface with an average wetting angle of 150.5° and a sliding angle of about 4.5° can be obtained on the Mg alloy by further chemical surface modification with perfluorodecyltriethoxysilane. This superhydrophobic surface has an interesting self-cleaning effect as well as good corrosion resistance in artificial hand sweat. In brief, this study provides a feasible way to prepare a superhydrophobic surface on the Mg-Nd alloy and reveals the effect of a superhydrophobic surface on the corrosion behavior of the Mg-Nd alloy, offering new technical insights into the corrosion protection of magnesium alloys. Full article
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37 pages, 17666 KiB  
Article
Effect of σ-Phase on the Strength, Stress Relaxation Behavior, and Corrosion Resistance of an Ultrafine-Grained Austenitic Steel AISI 321
by Vladimir I. Kopylov, Aleksey V. Nokhrin, Natalia A. Kozlova, Mikhail K. Chegurov, Mikhail Yu. Gryaznov, Sergey V. Shotin, Nikolay V. Melekhin, Nataliya Yu. Tabachkova, Ksenia E. Smetanina and Vladimir N. Chuvil’deev
Metals 2023, 13(1), 45; https://doi.org/10.3390/met13010045 - 24 Dec 2022
Cited by 4 | Viewed by 2328
Abstract
This paper reported the results of research into the effect of Equal Channel Angular Pressing (ECAP) temperature and 1-h annealing temperature on mechanical properties, stress-relaxation resistance, and corrosion resistance of austenitic steel AISI 321L with strongly elongated thin δ-ferrite particles in its microstructure. [...] Read more.
This paper reported the results of research into the effect of Equal Channel Angular Pressing (ECAP) temperature and 1-h annealing temperature on mechanical properties, stress-relaxation resistance, and corrosion resistance of austenitic steel AISI 321L with strongly elongated thin δ-ferrite particles in its microstructure. The formation of α′-martensite and fragmentation of austenite grains takes place during ECAP. Ultrafine-grained (UFG) steels demonstrate increased strength. However, we observed a reduced Hall–Petch coefficient as compared with coarse-grained (CG) steels due to the fragmentation of δ-ferrite particles. UFG steel specimens were found to have 2–3 times higher stress-relaxation resistance as compared with CG steels. For the first time, the high stress-relaxation resistance of UFG steels was shown to stem from a internal stress-relaxation mechanism, i.e., the interaction of lattice dislocations with non-equilibrium grain boundaries. Short-time 1-h annealing of UFG steel specimens at 600–800 °C was found to result in the nucleation of σ-phase nanoparticles. These nanoparticles affect the grain boundary migration, raise strength, and stress-relaxation resistance of steel but reduce the corrosion resistance of UFG steel. Lower corrosion resistance of UFG steel was shown to be related to the formation of α′-martensite during ECAP and the nucleation of σ-phase particles during annealing. Full article
(This article belongs to the Special Issue Environmentally-Assisted Degradation of Metals and Alloys)
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15 pages, 5943 KiB  
Article
A Survey on the Oxidation Behavior of a Nickel-Based Alloy Used in Natural Gas Engine Exhaust Valve Seats
by José Henrique Alano, Renato Luiz Siqueira, Claudio Beserra Martins Júnior, Rodrigo Silva, Guilherme dos Santos Vacchi and Carlos Alberto Della Rovere
Metals 2023, 13(1), 49; https://doi.org/10.3390/met13010049 - 24 Dec 2022
Cited by 2 | Viewed by 1662
Abstract
This study reports the oxidation behavior of a Ni-based alloy used in the manufacture of valve seats for automotive engine exhaust systems. Isothermal thermogravimetric analyses were carried out at temperatures of 660, 740, 860, and 900 °C under an oxygen atmosphere for up [...] Read more.
This study reports the oxidation behavior of a Ni-based alloy used in the manufacture of valve seats for automotive engine exhaust systems. Isothermal thermogravimetric analyses were carried out at temperatures of 660, 740, 860, and 900 °C under an oxygen atmosphere for up to 1 h. At 660 and 740 °C, only one stage was observed during the whole time studied. At this stage, the oxide layer was formed mainly by NiO + Cr2O3, following a linear oxidation law with a rate constant (Kl) on the order of magnitude of 10−6 kg/m2s and an apparent activation energy (Ea) of ~47 kJ/mol. At 860 and 900 °C, an identical first stage was observed with a transition to a different stage. In the second stage, the oxidation layer was composed of Cr2O3, and a parabolic oxidation law was followed with a rate constant (Kp) on the order of 10−8 kg2/m4s and Ea of ~128 kJ/mol. Moreover, the Ni-based alloy formed a dense and compact oxide layer after oxidation, with no apparent cavities, pores, or microcracks. Characterization techniques such as Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Raman Spectroscopy were carried out to characterize the formed oxide layer. Full article
(This article belongs to the Special Issue Composition Design and Damage Mechanism of Crystal Superalloys)
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18 pages, 8364 KiB  
Article
Challenges and Latest Developments in Diffusion Bonding of High-Magnesium Aluminium Alloy (Al-5056/Al-5A06) to Stainless Steels
by Amir A. Shirzadi, Chengcong Zhang, Muhammad Zeeshan Mughal and Peiyun Xia
Metals 2022, 12(7), 1193; https://doi.org/10.3390/met12071193 - 13 Jul 2022
Cited by 4 | Viewed by 2692
Abstract
The aim of this work was to investigate the challenges associated with bonding Al-Mg alloys and develop a new method for bonding these alloys to steels. During an extensive R&D project, over 80 attempts, using 11 methods, were made to bond Al-6 wt.% [...] Read more.
The aim of this work was to investigate the challenges associated with bonding Al-Mg alloys and develop a new method for bonding these alloys to steels. During an extensive R&D project, over 80 attempts, using 11 methods, were made to bond Al-6 wt.% Mg alloy (Al-5056/Al-5A06) to two types of stainless steels (heat-resistant 1Cr18Ni9Ti and conventional 316). Wide ranges of temperature (500 °C to 580 °C), pressure (0.5 MPa to 10 MPa) and time (1 min to 2 h) were used when direct diffusion bonding of these alloys. Then, effects of using various interlayers and brazing foils were investigated. The interlayers used in this work were gallium, pure titanium, copper and aluminium foils, aluminium 6061 alloy sheets, aluminium-silicon brazing foils, zinc and zinc alloy foils as well as an active brazing foil (known as Incusil-ABA containing silver, copper, indium and titanium). Several complex and multi-stage processes, using up to 3 different interlayers in the same joint, were also developed and assessed. Examination and assessment of the bonded samples, including failed attempts, paved the way of developing new methods for bonding these dissimilar materials. A number of samples with tensile strengths from 200 MPa to 226 MPa were made by using complex combinations of 2 or 3 interlayers and triple-stage bonding cycles. The highest recorded bond strength was 226 MPa in the as-bonded condition. This value is above the measured yield strength (134 MPa) and about 93% of the measured ultimate strength (243 MPa) of the parent Al-Mg alloy after it was subjected to the same bonding cycle. Since the use of complex processes was not feasible for bonding large components, a simpler and more practical bonding cycle was also developed in the project. Using the simpler process, joints with tensile strengths around 90 MPa could be made. This article also sheds light on the difficulties associated with brazing and soldering aluminium alloys with a high magnesium content. Full article
(This article belongs to the Special Issue Advances in Technology and Applications of Diffusion Bonding)
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13 pages, 6920 KiB  
Article
Effect of Process Control Agent on Microstructures and High-Temperature Oxidation Behavior of a Nickel-Based ODS Alloy
by Zhe Mao, Jing Li, Shi Liu and Liangyin Xiong
Metals 2022, 12(6), 1029; https://doi.org/10.3390/met12061029 - 17 Jun 2022
Viewed by 1683
Abstract
Two nickel-based oxide-dispersion-strengthened (ODS) alloys supplemented with different amounts of process control agent (PCA) were prepared. The microstructures including grains and nanometric oxides and the subsequent oxidation behavior of these ODS alloys were investigated. It was found that the distribution of nanometric oxides [...] Read more.
Two nickel-based oxide-dispersion-strengthened (ODS) alloys supplemented with different amounts of process control agent (PCA) were prepared. The microstructures including grains and nanometric oxides and the subsequent oxidation behavior of these ODS alloys were investigated. It was found that the distribution of nanometric oxides in the nickel-based ODS alloy is uniform and the grains are refined by adding a proper amount of PCA in the mechanical milling, while the blocking effect on the diffusion of active elements Y, Al and Ti among powders takes place with an excessive amount of PCA, resulting in the precipitation of large-size oxides in local areas of the alloy. After oxidation in air at 1000 °C for 200 h, the oxide scales on the surface of both nickel-based ODS alloys are composed of Cr2O3. As Y-rich oxide particles are precipitated in the matrix, the thickness of the oxide scale is significantly reduced compared with non-ODS alloys. However, due to the influence of grain boundaries on the diffusion of elements, the oxide scale on the surface of an alloy with finer grain size is thicker. The oxidation resistance of ODS alloys strongly depends on the exact manufacturing process. Full article
(This article belongs to the Special Issue High Temperature Corrosion or Oxidation of Metals and Alloys)
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13 pages, 3661 KiB  
Article
Effect of Austenitizing Temperature on the Work Hardening Behavior of Air-Hardening Steel LH800
by Xiang Luo, Zhenli Mi, Yanxin Wu, Yonggang Yang, Haitao Jiang and Kuanhui Hu
Metals 2022, 12(6), 1026; https://doi.org/10.3390/met12061026 - 16 Jun 2022
Cited by 1 | Viewed by 1622
Abstract
In this paper, we present the effect of austenitizing temperature on the work hardening behavior of air-hardening steel LH800 by evaluating the influence of austenitizing temperature on microstructure evolution and mechanical properties, using Hollomon, Differential Crussard–Jaoul (DC-J), and Modified C-J (M [...] Read more.
In this paper, we present the effect of austenitizing temperature on the work hardening behavior of air-hardening steel LH800 by evaluating the influence of austenitizing temperature on microstructure evolution and mechanical properties, using Hollomon, Differential Crussard–Jaoul (DC-J), and Modified C-J (MC-J) work hardening models. The results reveal that with an increase in austenitizing temperature, there is an increase in the percentage of martensite, along with an increase in the strength and hardness of the LH800 steel; on the other hand, there is a decrease in the plasticity. Austenitized at 825 °C, LH800 steel exhibits its highest strength and good plasticity, with a tensile strength of 897 MPa and an elongation of 13.6%. The comparison between the three strain hardening models revealed that the Hollomon model was the finest fit for the experimental data utilized and could illustrate the work hardening behavior of LH800 steel most suitably. This model manifests a two-stage work hardening mechanism; the first stage is related to the plastic deformation of ferrite phase, while the second stage deals with the co-deformation of ferrite and martensite/bainite phase. As austenitizing temperature increases, the work hardening ability of LH800 steel diminishes at each stage, the transition strain decreases, and the plastic deformation of martensite starts earlier. Full article
(This article belongs to the Special Issue Development and Performance Optimization of High-Strength Steels)
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12 pages, 6416 KiB  
Article
Structure, Mechanical Properties and Friction Characteristics of the Al-Mg-Sc Alloy Modified by Friction Stir Processing with the Mo Powder Addition
by Tatiana Kalashnikova, Evgeny Knyazhev, Denis Gurianov, Andrey Chumaevskii, Andrey Vorontsov, Kirill Kalashnikov, Natalya Teryukalova and Evgeny Kolubaev
Metals 2022, 12(6), 1015; https://doi.org/10.3390/met12061015 - 15 Jun 2022
Cited by 4 | Viewed by 1770
Abstract
In this study, samples of Al-Mg-Sc alloy were investigated after friction stir processing with the addition of Mo powder. Holes were drilled into 5 mm-thick aluminum alloy sheets into which Mo powder was added at percentages of 5, 10, and 15 wt%. The [...] Read more.
In this study, samples of Al-Mg-Sc alloy were investigated after friction stir processing with the addition of Mo powder. Holes were drilled into 5 mm-thick aluminum alloy sheets into which Mo powder was added at percentages of 5, 10, and 15 wt%. The workpieces with different powder contents were then subjected to four passes of friction stir processing. Studies have shown that at least three tool passes are necessary and sufficient for a uniform Mo powder distribution in the stir zone, but the number of required passes is higher with an increase in the Mo content. Due to the temperature specifics of the processing, no intermetallic compounds are formed in the stir zone, and Mo is distributed as separate particles of different sizes. The average ultimate strength of the composite materials after four passes is approximately 387 MPa in the stir zone, and the relative elongation of the material changes from 15 to 24%. The dry sliding friction test showed that the friction coefficient of the material decreases with the addition of 5 wt% Mo, but with a further increase in Mo content, returns to the original material values. Full article
(This article belongs to the Special Issue Mechanical Properties of Metals Welding Joints)
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25 pages, 8807 KiB  
Article
Biofilm Development on Carbon Steel by Iron Reducing Bacterium Shewanella putrefaciens and Their Role in Corrosion
by Sachie Welikala, Saad Al-Saadi, Will P. Gates, Christopher Panter and R. K. Singh Raman
Metals 2022, 12(6), 1005; https://doi.org/10.3390/met12061005 - 12 Jun 2022
Cited by 4 | Viewed by 2058
Abstract
Microscopic, electrochemical and surface characterization techniques were used to investigate the effects of iron reducing bacteria (IRB) biofilm on carbon steel corrosion for 72 and 168 h under batch conditions. The organic nutrient availability for the bacteria was varied to evaluate biofilms formed [...] Read more.
Microscopic, electrochemical and surface characterization techniques were used to investigate the effects of iron reducing bacteria (IRB) biofilm on carbon steel corrosion for 72 and 168 h under batch conditions. The organic nutrient availability for the bacteria was varied to evaluate biofilms formed under nutritionally rich, as compared to nutritionally deficient, conditions. Focused ion beam-scanning electron microscopy (FIB-SEM) was used to investigate the effect of subsurface biofilm structures on the corrosion characteristics of carbon steel. Hydrated biofilms produced by IRB were observed under environmental scanning electron microscope (ESEM) with minimal surface preparation, and the elemental composition of the biofilms was investigated using energy dispersive spectroscopy (EDX). Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) was used to provide information on the organic and inorganic chemical makeup of the biofilms. Electrochemical techniques employed for assessing corrosion, by open circuit potential, linear polarization and potentiodynamic polarization tests indicated no significant difference in the corrosion resistance for carbon steel in IRB-inoculated, compared to the abiotic solutions of common Postgate C after 72 and 168 h. However, the steel was found to be more susceptible to corrosion when the yeast extract was removed from the biotic environment for the 168 h test. In the absence of yeast nutrient, it is postulated that IRB received energy by transforming the protective film of Fe3+ into more soluble Fe2+ products. Full article
(This article belongs to the Special Issue Advances in Corrosion and Protection of Materials)
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15 pages, 6999 KiB  
Article
Effect of Two-Step High Temperature Treatment on Phase Transformation and Microstructure of V-Bearing Bainitic Steel
by Bo Lv, Dongxin Yin, Dongyun Sun, Zhinan Yang, Xiaoyan Long and Zeliang Liu
Metals 2022, 12(6), 983; https://doi.org/10.3390/met12060983 - 07 Jun 2022
Viewed by 1474
Abstract
The effects of VC precipitation on phase transformation, microstructure, and mechanical properties were studied by controlling two-step isothermal treatment, i.e., austenization followed by intercritical transformation. The results show that the bainite transformation time of 950 °C–860 °C treatment and 950 °C–848 °C treatment [...] Read more.
The effects of VC precipitation on phase transformation, microstructure, and mechanical properties were studied by controlling two-step isothermal treatment, i.e., austenization followed by intercritical transformation. The results show that the bainite transformation time of 950 °C–860 °C treatment and 950 °C–848 °C treatment is shorter than that of 950 °C single-step treatment. This is related to the isothermal ferrite transformation in the intercritical transformation range. The formation of ferrite nuclei increases the density of medium temperature bainite nucleation sites and decrease the bainite nucleation activation energy. At the same time, a large number of VC particles are precipitated. The additional VC particles provide numbers of preferential nucleation sites. The toughness of the specimen treated at 950~870 °C is improved, which is related to the large proportion of high angle grain boundaries. High angle grain boundaries can hinder crack propagation or change the direction of crack propagation. The specimen treated at 950 °C–848 °C exhibits large proportion of low angle grain boundaries, which is beneficial for the strength improvement. Full article
(This article belongs to the Special Issue High Performance Bainitic Steels)
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10 pages, 2383 KiB  
Article
A New Strategy for Dissimilar Material Joining between SiC and Al Alloys through Use of High-Si Al Alloys
by Yongjing Yang, Ayan Bhowmik, Jin Lee Tan, Zehui Du and Wei Zhou
Metals 2022, 12(5), 887; https://doi.org/10.3390/met12050887 - 23 May 2022
Cited by 1 | Viewed by 2118
Abstract
Joining metals and ceramics plays a crucial role in many engineering applications. The current research aims to develop a simple and convenient approach for dissimilar material joining between SiC and Al alloys. In this work, Al alloys with Si contents varying from 7 [...] Read more.
Joining metals and ceramics plays a crucial role in many engineering applications. The current research aims to develop a simple and convenient approach for dissimilar material joining between SiC and Al alloys. In this work, Al alloys with Si contents varying from 7 wt.% to 50 wt.% were bonded with SiC at a high temperature of 1100 °C by a pressure-less bonding process in a vacuum furnace, and shear tests were carried out to study the bonding strength. When using low-Si Al alloys to bond with SiC, the bonding strength was very low. The bonding strength of Al/SiC joints increased significantly through the use of high-Si Al alloys with 30 wt.% and 50 wt.% Si. The shear strength achieved (28.8 MPa) is far higher than those reported previously. The remarkable improvement in bonding strength is attributed to the suppression of brittle interfacial products and reduced thermal stresses. This research provides a new strategy for joining between SiC and a wide range of Al alloys through the use of high-Si Al alloys as the interlayers. Full article
(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)
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31 pages, 6813 KiB  
Article
The Holes of Zn Phosphate and Hot Dip Galvanizing on Electrochemical Behaviors of Multi-Coatings on Steel Substrates
by Thiago Duarte, Yuri A. Meyer and Wislei R. Osório
Metals 2022, 12(5), 863; https://doi.org/10.3390/met12050863 - 18 May 2022
Cited by 26 | Viewed by 2331
Abstract
The aim of this investigation is focused on the evaluation of distinctive coatings commonly applied in the automotive industry. The resulting corrosion behavior is analyzed by using electrochemical impedance spectroscopy (EIS), equivalent circuit (EC) and potentiodynamic polarization curves. The novelty concerns a comparison [...] Read more.
The aim of this investigation is focused on the evaluation of distinctive coatings commonly applied in the automotive industry. The resulting corrosion behavior is analyzed by using electrochemical impedance spectroscopy (EIS), equivalent circuit (EC) and potentiodynamic polarization curves. The novelty concerns a comparison between tricationic phosphate (TCP), cataphoretic electrodeposition (CED) of an epoxy layer, TCP + CED and HDG (hot-dip galvanized) + TCP + CED multi-coatings. Both the naturally deposited and defect-induced damage (incision) coatings are examined. The experimental impedance parameters and corrosion current densities indicate that multi-coating system (HDG + TCP + CED layers) provides better protection. Both planar and porous electrode behaviors are responsible to predict the corrosion mechanism of the majority of samples examined. Although induced-damage samples reveal that corrosion resistances decreased up to 10×, when compared with no damaged samples, the same trend of the corrosion protection is maintained, i.e., TCP < CED < TCP + CED < HDG + TCP + CED. It is also found that the same trend verified by using electrochemical parameters is also observed when samples are subjected under salt spray condition (500 h). It is also found that porous electrode behavior is not a deleterious aspect to corrosion resistance. It is more intimately associated with initial thickness coating, while corrosion resistance is associated with adhesion of the CED layer on TCP coating. The results of relative cost-to-efficiency to relative coating density ratios are associated with fact that a CED coating is necessary to top and clear coating applications and the TCP + CED and the HDG/TCP + CED coating systems exhibit the best results. Full article
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13 pages, 3133 KiB  
Article
An Improved Approach to Manufacture Carbon Nanotube Reinforced Magnesium AZ91 Composites with Increased Strength and Ductility
by Samaneh Nasiri, Guang Yang, Erdmann Spiecker and Qianqian Li
Metals 2022, 12(5), 834; https://doi.org/10.3390/met12050834 - 13 May 2022
Cited by 3 | Viewed by 1979
Abstract
Multiwalled carbon nanotubes (MWCNTs) are decorated with Pt nanoparticles by a “layer-by-layer” approach using poly (sodium 4-styrene sulfonate) (PSS) and poly (diallyl dimethylammonium chloride) (PDDA). Transmission electron microscopy (TEM) images and Energy Dispersive X-ray (EDX) analysis of the samples confirm Pt deposition on [...] Read more.
Multiwalled carbon nanotubes (MWCNTs) are decorated with Pt nanoparticles by a “layer-by-layer” approach using poly (sodium 4-styrene sulfonate) (PSS) and poly (diallyl dimethylammonium chloride) (PDDA). Transmission electron microscopy (TEM) images and Energy Dispersive X-ray (EDX) analysis of the samples confirm Pt deposition on surfaces of CNTs. Dispersibility and dispersion stability of MWCNTs in the solvents are enhanced when MWCNTs are coated with Pt nanoparticles. Mg AZ91 composites reinforced with MWCNTs are then produced by a melt stirring process. Compression tests of the composites show that adding 0.05% wt Pt-coated MWCNTs in AZ91 improves the composite’s mechanical properties compared to the pure AZ91 and pristine MWCNT/AZ91. Fracture surface analysis of the composite using a scanning electron microscope (SEM) shows individual pulled out MWCNTs in the case of the Pt-coated MWCNT/AZ91 composites. This finding can be attributed to the uniform dispersion of Pt-coated MWCNTs in Mg due to the improved wettability of Pt-coated MWCNTs in Mg melts. The study of the pull-out behaviour of pristine and Pt-coated CNTs from an Mg matrix using molecular dynamics simulation supports this interpretation. Full article
(This article belongs to the Special Issue Advances in High Strength–Ductility Synergy Materials)
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14 pages, 4127 KiB  
Article
Real-Time Quality Monitoring of Laser Cladding Process on Rail Steel by an Infrared Camera
by Pornsak Srisungsitthisunti, Boonrit Kaewprachum, Zhigang Yang and Guhui Gao
Metals 2022, 12(5), 825; https://doi.org/10.3390/met12050825 - 11 May 2022
Cited by 5 | Viewed by 4041
Abstract
Laser cladding is considered to be a highly complex process to set up and control because it involves several parameters, such as laser power, laser scanning speed, powder flow rate, powder size, etc. It has been widely studied for metal-part coating and repair [...] Read more.
Laser cladding is considered to be a highly complex process to set up and control because it involves several parameters, such as laser power, laser scanning speed, powder flow rate, powder size, etc. It has been widely studied for metal-part coating and repair due to its advantage in controllable deposited materials on a small target substrate with low heat-affected distortion. In this experiment, laser cladding of U75V and U20Mn rail steels with Inconel 625 powder was captured by an infrared camera with image analysis software to monitor the laser cladding process in order to determine the quality of the cladded substrates. The cladding temperature, thermal gradient, spot profile, and cooling rate were determined from infrared imaging of the molten pool. The results showed that cladding temperature and molten pool’s spot closely related to the laser cladding process condition. Infrared imaging provided the cooling rate from a temperature gradient which was used to correctly predict the microhardness and microstructure of the HAZ region. This approach was able to effectively detect disturbance and identify geometry and microstructure of the cladded substrate. Full article
(This article belongs to the Special Issue High Performance Bainitic Steels)
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14 pages, 9661 KiB  
Article
Microstructure Characteristics and Wear Performance of a Carburizing Bainitic Ferrite + Martensite Si/Al-Rich Gear Steel
by Yanhui Wang, Qingsong He, Qian Yang, Dong Xu, Zhinan Yang and Fucheng Zhang
Metals 2022, 12(5), 822; https://doi.org/10.3390/met12050822 - 10 May 2022
Cited by 3 | Viewed by 2041
Abstract
In this paper, a new low-carbon alloy gear steel is designed via Si/Al alloying. The carburizing and austempering, at a temperature slightly higher than the martensitic transformation point (Ms) of the surface and much lower than the Ms of the core, for different [...] Read more.
In this paper, a new low-carbon alloy gear steel is designed via Si/Al alloying. The carburizing and austempering, at a temperature slightly higher than the martensitic transformation point (Ms) of the surface and much lower than the Ms of the core, for different times, were carried out on the newly designed gear steel. After heat treatment, a series of different microstructures (superfine bainitic ferrite + retained austenite, superfine bainitic ferrite + martensite + retained austenite, and martensite + retained austenite) were obtained on the surface, whilst the low-carbon lath martensitic microstructure was obtained in the core. The microstructure of the surface was examined using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The phase composition was analyzed using X-ray diffraction (XRD). The hardness and wear resistance of the surface as well as the hardness distribution of carburizing layer of the samples with different microstructures were studied. The results show that the Si/Al-rich gear steel, after carburizing and austempering at 200 °C for 8 h, not only has excellent mechanical properties but also has high wear resistance, which meets the technical requirements of heavy-duty gear steel. The research work in this paper can provide a data reference for the application of carburized steel with mixed microstructures of bainitic ferrite and martensite in the design of heavy-duty gear. Full article
(This article belongs to the Special Issue High Performance Bainitic Steels)
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21 pages, 5807 KiB  
Article
Observing the Effect of Grain Refinement on Crystal Growth of Al and Mg Alloys during Solidification Using In-Situ Neutron Diffraction
by Abdallah Elsayed, Francesco D’Elia, Comondore Ravindran and Dimitry Sediako
Metals 2022, 12(5), 793; https://doi.org/10.3390/met12050793 - 04 May 2022
Cited by 4 | Viewed by 1844
Abstract
The present research uses in-situ neutron diffraction to examine the effect of grain refinement on grain growth during solidification of Al-5 wt.% Cu and Mg-5 wt.% Zn alloys. The alloys were grain refined through additions of Al-5Ti-1B and Zr, respectively. The in-situ neutron [...] Read more.
The present research uses in-situ neutron diffraction to examine the effect of grain refinement on grain growth during solidification of Al-5 wt.% Cu and Mg-5 wt.% Zn alloys. The alloys were grain refined through additions of Al-5Ti-1B and Zr, respectively. The in-situ neutron diffraction experiments were carried out by heating the alloys to temperatures above the liquidus and subsequently cooling in 5 or 10 °C temperature steps to temperatures below solidus, while being irradiated by thermal neutrons. With the addition of grain refiners, grain size reductions of 92% were observed for both the Al-5 wt.% Cu and Mg-5 wt.% Zn alloys. The refined and unrefined Al-5 wt.% Cu alloys contained α-Al with Al2Cu along the grain boundary regions. Differences in Al2Cu morphology were observed in the grain refined alloys. The Mg-5 wt.% Zn alloy contained MgZn intermetallic phases with primary Mg. The refined Mg-5 wt.% Zn-0.7 wt.% Zr alloy contained Mg, MgZn and Zn2Zr phases. In-situ neutron diffraction enabled quantification of individual plane solid fraction growth for the α-Al and Al2Cu phases in the Al-Cu alloys, and for α-Mg in the Mg alloys. For the unrefined Al-5 wt.% Cu, the coarse microstructure resulted in a rapid solid fraction rise at temperatures just below liquidus followed by a gradual increase in solid fraction until the sample was fully solid. The grain-refined Al-5 wt.% Cu alloys showed a columnar to equiaxed microstructure transition and a more gradual growth in fraction solid throughout solidification. For the Mg-5 wt.% Zn alloy, the more packed (0002) and (101¯1) α-Mg plane intensities grew at a slower rate than the (101¯0) plane intensity, resulting in an irregular grain structure. With the addition of the Zr grain refiner, the Mg-5 wt.% Zn-0.7 wt.% Zr alloy had (101¯0), (0002) and (101¯1) planes intensities all increasing at similar rates, especially at the early stages of solidification. FactSage™ (version 6.4, Montréal, QC, Canada) equilibrium solidification models followed the fraction solid curves developed by tracking the fastest growing planes of the Mg alloys. Full article
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8 pages, 5218 KiB  
Article
Electrochemical Corrosion Resistance of Mg Alloy ZK60 in Different Planes with Respect to Extrusion Direction
by G. Keerthiga, Dandapani Vijayshankar, MJNV Prasad, Mirco Peron, Jafar Albinmousa and RK Singh Raman
Metals 2022, 12(5), 782; https://doi.org/10.3390/met12050782 - 30 Apr 2022
Cited by 6 | Viewed by 1873
Abstract
The electrochemical corrosion resistance of a Mg-Zn-Zr alloy, ZK60, in different planes with respect to the extrusion direction was investigated in 3.5 wt% NaCl. The motivation of this study lies in the influence of extrusion on the grain size, texture and precipitation characteristics [...] Read more.
The electrochemical corrosion resistance of a Mg-Zn-Zr alloy, ZK60, in different planes with respect to the extrusion direction was investigated in 3.5 wt% NaCl. The motivation of this study lies in the influence of extrusion on the grain size, texture and precipitation characteristics of magnesium alloys, and the profound role of these characteristics in the corrosion resistance of the alloys. Corrosion resistance was found to be considerably superior in the plane transverse to the extrusion direction (TD) than in the extrusion direction (ED) or normal to the extrusion direction (ND). The difference in the corrosion resistance was attributed to the variations in microstructural features in the TD, ED and ND directions. Full article
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3 pages, 162 KiB  
Editorial
Recent Developments in Medium and High Manganese Steels
by Colin P. Scott
Metals 2022, 12(5), 743; https://doi.org/10.3390/met12050743 - 27 Apr 2022
Cited by 2 | Viewed by 1731
Abstract
A huge amount of intellectual effort is currently being devoted to the study of medium and high manganese steels due to the diverse and impressive mechanical properties that can be achieved with these steels [...] Full article
(This article belongs to the Special Issue Recent Developments in Medium and High Manganese Steels)
13 pages, 5018 KiB  
Article
Investigation on Corrosion Resistance Properties of 17-4 PH Bound Metal Deposition As-Sintered Specimens with Different Build-Up Orientations
by Pietro Forcellese, Tommaso Mancia, Michela Simoncini and Tiziano Bellezze
Metals 2022, 12(4), 588; https://doi.org/10.3390/met12040588 - 30 Mar 2022
Cited by 6 | Viewed by 3144
Abstract
Additive manufacturing is a promising and emerging technology that can transform the global manufacturing and logistics by cutting costs and times of production. Localized corrosion resistance properties of 0°, 45°, and 90° build-up orientations of 17-4 PH as-sintered samples, manufactured by means of [...] Read more.
Additive manufacturing is a promising and emerging technology that can transform the global manufacturing and logistics by cutting costs and times of production. Localized corrosion resistance properties of 0°, 45°, and 90° build-up orientations of 17-4 PH as-sintered samples, manufactured by means of Bound Metal Deposition (BMD), have been investigated by electrochemical and morphological investigations. The cyclic potentiodynamic polarization curves and the open circuit potential monitoring, together with potential drop analysis, revealed that the BMD localized corrosion resistance properties were lowered if compared to a wrought 17-4 PH: a characteristic anodic behavior and many drops in potential were recorded for BMD, whilst the wrought specimens presented a typical passive behavior with pitting corrosion. Morphological investigations by scanning electron microscopy and energy-dispersive X-ray analysis revealed the presence of porosities and defects, especially for the 90° build-up orientation, and inclusions of SiO2. The 45° build-up orientation showed the best corrosion resistance properties among all the BMD specimens, even though defects and porosities were observed, suggesting that their morphology and geometry influenced the overall corrosion behavior. Full article
(This article belongs to the Special Issue Corrosion and Protection of Stainless Steels)
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24 pages, 2796 KiB  
Review
A Review of Corrosion under Insulation: A Critical Issue in the Oil and Gas Industry
by Qing Cao, Thunyaluk Pojtanabuntoeng, Marco Esmaily, Sebastian Thomas, Michael Brameld, Ayman Amer and Nick Birbilis
Metals 2022, 12(4), 561; https://doi.org/10.3390/met12040561 - 25 Mar 2022
Cited by 22 | Viewed by 10126
Abstract
Corrosion under insulation (CUI) is defined as any form of external corrosion that occurs on the underlying metal beneath insulated equipment, due to water ingress through the insulation layer. This type of corrosion is frequently observed in oil and gas production, where insulated [...] Read more.
Corrosion under insulation (CUI) is defined as any form of external corrosion that occurs on the underlying metal beneath insulated equipment, due to water ingress through the insulation layer. This type of corrosion is frequently observed in oil and gas production, where insulated piping is prevalent, and has historically remained a predominant materials integrity issue. The prediction and direct visualisation of CUI are challenging tasks because of the coverage of the insulation layer(s) and any external jacketing or cladding. Several factors, including the local/ambient environment, system design, and the piping installation process, can influence how CUI initiates and propagates. In this review, CUI background, CUI monitoring, and CUI mitigation strategies are discussed. Full article
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15 pages, 4157 KiB  
Article
Effect of Diffusion on Dissimilar Welded Joint between Al0.8CoCrFeNi High-Entropy Alloy and S235JR Structural Steel
by Ionelia Voiculescu, Victor Geanta, Elena Violeta Stefanescu, George Simion and Elena Scutelnicu
Metals 2022, 12(4), 548; https://doi.org/10.3390/met12040548 - 24 Mar 2022
Cited by 6 | Viewed by 2488
Abstract
This research focused on the investigation of the metallurgical behavior of the Al0.8CoCrFeNi high-entropy alloy and S235JR structural steel, welded with (Ni, Fe)-rich filler metal, by the Gas Tungsten Arc Welding (GTAW) method. The electric arc and the welding pool were [...] Read more.
This research focused on the investigation of the metallurgical behavior of the Al0.8CoCrFeNi high-entropy alloy and S235JR structural steel, welded with (Ni, Fe)-rich filler metal, by the Gas Tungsten Arc Welding (GTAW) method. The electric arc and the welding pool were protected against the contamination with gases from the environment, by employing high-purity Ar 4.8 inert gas that plays an important role in reducing the oxidation effects and the development of cracks in the weld and the adjacent areas. The microstructure and microhardness analysis did not reveal the existence of fragile phases, cracks, inadequate penetration, or other imperfections, showing an appropriate adhesion between the deposited metal and the substrates. At the interface between the Ni-rich weld metal and the high-entropy alloy, a higher hardness (448 HV0.2) than in the base material (358 HV0.2) was measured. Energy-dispersive X-ray analysis (EDS), performed at the interface between the weld metal and the base materials, did not show significant modifications of Co, Fe, and Cr percentages. However, during the investigation, significant variations in Al and Ni concentrations were observed, caused by the fast diffusion of chemical elements, and the development of hard (Ni, Al)-rich compounds. In some areas of the deposited metal, located at a distance of about 10 µm from the interface, the percentages of Ni and Al were higher than in the high-entropy alloy base material, being around 41% by weight Ni and over 13% by weight Al, while the concentrations of the Co, Cr, and Fe elements proportionally decreased (i.e., approximately 14% by weight Co, 12% by weight Cr, and 17% by weight Fe). The development of Ni3Al and NiAl compounds was also noticed, whose formation was determined by the local chemical concentration and the temperature reached in the vicinity of the diffusion zone. The XRD analysis showed a group of X-ray peaks in the Al0.8CrFeCoNi alloy that corresponded to both α-type—BCC and FCC phases. The crystallite size of the high-entropy alloy investigated was found to be 22.05 nm. Despite the diffusion phenomenon, if filler materials and process parameters are appropriately selected, quality joints of high-entropy alloys and structural steels can be carried out under good welding conditions. Full article
(This article belongs to the Special Issue High-Productivity Welding of Metals and Alloys)
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31 pages, 102999 KiB  
Review
The Influence of Precipitation, High Levels of Al, Si, P and a Small B Addition on the Hot Ductility of TWIP and TRIP Assisted Steels: A Critical Review
by Barrie Mintz and Abdullah Qaban
Metals 2022, 12(3), 502; https://doi.org/10.3390/met12030502 - 16 Mar 2022
Cited by 12 | Viewed by 2326
Abstract
The hot ductility of Transformation Induced Plasticity (TRIP) and Twinning Induced Plasticity (TWIP) steels is reviewed, concentrating on the likelihood of cracking occurring on continuous casting during the straightening operation. In this review, the influence of high levels of Al, Si, P, Mn [...] Read more.
The hot ductility of Transformation Induced Plasticity (TRIP) and Twinning Induced Plasticity (TWIP) steels is reviewed, concentrating on the likelihood of cracking occurring on continuous casting during the straightening operation. In this review, the influence of high levels of Al, Si, P, Mn and C on their hot ductility will be discussed as well as the important role B can play in improving their hot ductility. Of these elements, Al has the worst influence on ductility but a high Al addition is often needed in both TWIP and TRIP steels. AlN precipitates are formed often as thin coatings covering the austenite grain surfaces favouring intergranular failure and making them difficult to continuous cast without cracks forming. Furthermore, with TWIP steels the un-recrystallised austenite, which is the state the austenite is when straightening, suffers from excessive grain boundary sliding, so that the ductility often decreases with increasing temperature, resulting in the RA value being below that needed to avoid cracking on straightening. Fortunately, the addition of B can often be used to remedy the deleterious influence of AlN. The influence of precipitation hardeners (Nb, V and Ti based) in strengthening the room temperature yield strength of these TWIP steels and their influence on hot ductility is also discussed. Full article
(This article belongs to the Special Issue Continuous Casting and Hot Ductility of Advanced High-Strength Steels)
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14 pages, 14185 KiB  
Article
Corrosion Behavior of Gravity Cast and High-Pressure Die-Cast AM60 Mg Alloys with Ca and Y Addition
by Hui Yu, Xin Yang, Wei Yu, Youngmin Kim, Shaoming Kang, Lixin Huang, Bongsun You, Chunhai Liu, Kwangseon Shin and Weimin Zhao
Metals 2022, 12(3), 495; https://doi.org/10.3390/met12030495 - 15 Mar 2022
Viewed by 2005
Abstract
In this study, the microstructure and related corrosion behavior of AM60 alloys with/without Ca and Y addition upon gravity casting (GC) and high-pressure die-casting (HPDC) are investigated by means of SEM/EDS characterization, immersion/salt spray test, hydrogen releasing, as well as electrochemistry examination. When [...] Read more.
In this study, the microstructure and related corrosion behavior of AM60 alloys with/without Ca and Y addition upon gravity casting (GC) and high-pressure die-casting (HPDC) are investigated by means of SEM/EDS characterization, immersion/salt spray test, hydrogen releasing, as well as electrochemistry examination. When utilizing GC, AM60 alloy with Ca and Y addition (named AZXW6000 alloy) has better corrosion resistance compared with AM60 alloy. Thanks to grain refinement and second phase networks introduced in HPDC, the anti-corrosion properties of the AM alloy seem much better than those of the GC counterpart. The corrosion mechanism of both GCed and HPDCed AM60-based alloys is also investigated in detail. The inspiration from present work can provide more thinking for developing high corrosion-resistant Mg alloys using different casting methods. Full article
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10 pages, 29014 KiB  
Article
Investigation on Blood Compatibility of Cu/Ti Metal Coating Prepared via Various Bias Voltages and Copper Content
by Qiong Hu, Hengquan Liu, Fei Gao, Xi Yang, Junfeng Li, Ren Liu, Zexuan Liu and Dongfang Wang
Metals 2022, 12(3), 435; https://doi.org/10.3390/met12030435 - 01 Mar 2022
Cited by 1 | Viewed by 1887
Abstract
Surface modification of some metal coatings is usually used to improve the blood compatibility of biomaterials; however, some aspects of the bological properties of metal coatings cannot be adjusted via the content of each component. In this work, Cu/Ti metal coatings with various [...] Read more.
Surface modification of some metal coatings is usually used to improve the blood compatibility of biomaterials; however, some aspects of the bological properties of metal coatings cannot be adjusted via the content of each component. In this work, Cu/Ti metal coatings with various amounts of copper content were prepared by the physical vapor deposition (PVD) method, and the influence of deposition bias was further investigated. Phase structure, element composition and surface morphology were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy, respectively. The hemolysis ratio, platelet adhesion and protein adsorption were applied to evaluate the blood compatibility. The results show that a Cu/Ti coating of uniform quality can be obtained; the dispersion of the deposition and copper content is regulated by the number of copper sheets, but the deposition bias does not obviously affect the copper content of the Cu/Ti coating. The hemolysis rate of the Cu/Ti coating is less than 0.4%, the degree of platelet adhesion is significantly reduced on Cu/Ti coatings compared to control samples, and the contact angle of all coatings is greater than that of pure titanium. The largest adsorption capacity of BSA was found on the coating with the deposition bias voltage of −40 V. The number of copper flakes is increased, and the adsorption of FIB on the Cu/Ti coating surface is reduced. Therefore, Cu/Ti coatings prepared via this deposition method have potential for applications to regulate blood compatibility and surface performance. Full article
(This article belongs to the Special Issue Advances in Stability of Metallic Implants)
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20 pages, 9493 KiB  
Article
Effect of Intercritical Annealing Parameters and Starting Microstructure on the Microstructural Evolution and Mechanical Properties of a Medium-Mn Third Generation Advanced High Strength Steel
by Kazi M. H. Bhadhon, Xiang Wang, Elizabeth A. McNally and Joseph R. McDermid
Metals 2022, 12(2), 356; https://doi.org/10.3390/met12020356 - 18 Feb 2022
Cited by 12 | Viewed by 2466
Abstract
A prototype medium-Mn TRIP steel (0.2 C–6 Mn–1.7 Si–0.4 Al–0.5 Cr (wt %)) with a cold-rolled tempered martensite (CR) and martensitic (M) starting microstructures was subjected to continuous galvanizing line (CGL) compatible heat treatments. It was found that the M starting microstructures achieved [...] Read more.
A prototype medium-Mn TRIP steel (0.2 C–6 Mn–1.7 Si–0.4 Al–0.5 Cr (wt %)) with a cold-rolled tempered martensite (CR) and martensitic (M) starting microstructures was subjected to continuous galvanizing line (CGL) compatible heat treatments. It was found that the M starting microstructures achieved greater than 0.30 volume fraction of retained austenite and target 3G properties (UTS × TE ≥ 24,000 MPa%) using an intercritical annealing temperature (IAT) of 675 °C with an IA holding time of 60–360 s, whereas the CR microstructure required an IAT of 710 °C and annealing times of 360 s or greater to achieve comparable fractions of retained austenite and target 3G properties. This was attributed to the rapid austenite reversion kinetics for the M starting microstructures and rapid C partitioning from the C supersaturated martensite, providing chemical and mechanical stability to the retained austenite, thereby allowing for a gradual deformation-induced transformation of retained austenite to martensite—the TRIP effect—and the formation of nano-scale planar faults in the retained austenite (TWIP effect), such that a high work-hardening rate was maintained to elongation of greater than 0.20. Overall, it was concluded that the prototype steel with the M starting microstructure is a promising candidate for CGL processing for 3G AHSS properties. Full article
(This article belongs to the Special Issue Recent Developments in Medium and High Manganese Steels)
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15 pages, 7246 KiB  
Article
Role of Hot Rolling in Microstructure and Texture Development of Strip Cast Non-Oriented Electrical Steel
by Haitao Jiao, Xinxiang Xie, Xinyi Hu, Longzhi Zhao, Raja Devesh Kuma Misra, Dejia Liu, Yanchuan Tang and Yong Hu
Metals 2022, 12(2), 354; https://doi.org/10.3390/met12020354 - 18 Feb 2022
Cited by 4 | Viewed by 2877
Abstract
In this study, the effect of the hot-cold rolling process on the evolution of the microstructure, texture and magnetic properties of strip-cast non-oriented electrical steel was investigated by introducing hot rolling with different reductions. The results indicate that hot rolling with an appropriate [...] Read more.
In this study, the effect of the hot-cold rolling process on the evolution of the microstructure, texture and magnetic properties of strip-cast non-oriented electrical steel was investigated by introducing hot rolling with different reductions. The results indicate that hot rolling with an appropriate reduction, such as the 20% used in this study, increases the shear bands and {100} deformed microstructure in the cold roll sheet. As a result, in our study, enhanced η and Cube recrystallization texture and the improved magnetic induction were obtained. However, hot rolling with excessive reduction (36–52%) decreased the shear bands and increased the α-oriented deformation microstructure with low stored energy. It enhanced the α recrystallization texture and weakened the η texture, resulting in a decrease in the magnetic induction. In addition, hot rolling promoted the precipitation of supersaturated solid solution elements in the as-cast strip, thereby affecting the subsequent microstructure evolution and the optimization of its magnetic properties. Full article
(This article belongs to the Special Issue Texture, Microstructure and Properties of Electrical Steels)
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13 pages, 3792 KiB  
Article
Use of Porous Titanium Trabecular as a Bone Defect Regenerator: In Vivo Study
by Ana Isabel Torres Pérez, Mariano Fernández Fairén, Ángel Antonio Torres Pérez and Javier Gil Mur
Metals 2022, 12(2), 327; https://doi.org/10.3390/met12020327 - 12 Feb 2022
Cited by 2 | Viewed by 1864
Abstract
The application of porous materials is increasingly being used in orthopaedic surgery due to its good results. Bone growth within the pores results in excellent mechanical fixation with the bone, as well as good bone regeneration. The pores, in addition to being colonised [...] Read more.
The application of porous materials is increasingly being used in orthopaedic surgery due to its good results. Bone growth within the pores results in excellent mechanical fixation with the bone, as well as good bone regeneration. The pores, in addition to being colonised by bone, produce a decrease in the modulus of elasticity that favours the transfer of loads to the bone. This research shows the results of an experimental study where we have created critical osteoperiosteal defects of 10 mm on rabbit’s radius diaphysis. In one group of 10 rabbits (experimental group) we have implanted a bioactive porous titanium cylinder, and in another group we have allowed spontaneous regeneration (control group). Mechanical tests were performed to assess the material. Image diagnostic techniques (X-ray, scanner and 3D scan: there are no references on the literature with the use of CT-scan in bone defects) and histological and histomorphometric studies post-op and after 3, 6 and 12 months after the surgery were performed. All the control cases went through a pseudoarthrosis. In 9 of the 10 cases of the experimental group complete regeneration was observed, with a normal cortical-marrow structure established at 6 months, similar to normal bone. Titanium trabecular reached a bone percentage of bone inside the implant of 49.3% on its surface 3 months post-op, 75.6% at 6 months and 81.3% at 12 months. This porous titanium biomaterial has appropriate characteristics to allow bone ingrowth, and it can be proposed as a bone graft substitute to regenerate bone defects, as a scaffold, or as a coating to achieve implant osteointegration. Full article
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12 pages, 4228 KiB  
Article
Rejuvenation-to-Relaxation Transition Induced by Elastostatic Compression and Its Effect on Deformation Behavior in a Zr-Based Bulk Metallic Glass
by Jingxian Cui, Qiang Luo, Siyi Di, Zhengguo Zhang and Baolong Shen
Metals 2022, 12(2), 282; https://doi.org/10.3390/met12020282 - 04 Feb 2022
Cited by 7 | Viewed by 1728
Abstract
The effect of uniaxial elastostatic compression on the deformation behavior of the Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit1) bulk metallic glass (BMG) was reported. The as-cast alloy was pre-compressed under various time (20, 40 and 60 h) at [...] Read more.
The effect of uniaxial elastostatic compression on the deformation behavior of the Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit1) bulk metallic glass (BMG) was reported. The as-cast alloy was pre-compressed under various time (20, 40 and 60 h) at a preloading level of 87% of its yield strength. It was found that elastostatic compression can lead to structural rejuvenation or relaxation depending on the pre-compression time. Elastostatic compression, for 40 h, increased the free volume and improved the plasticity of the BMGs from 1.4% to 3.4%, but preloading for 60 h decreased the free volume and worsened the plasticity. In addition, the heterogeneous structure evolution during creep deformation has been analyzed by the Maxwell-Voigt model with two Kelvin units, revealing that more (less) defects with larger size are activated after elastostatic compression treatment for 40 h (60 h). This work sheds new light on the correlation between heterogeneous structure and plasticity/creep behaviors of Zr-based BMGs. Full article
(This article belongs to the Section Entropic Alloys and Meta-Metals)
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17 pages, 8727 KiB  
Article
Effects of Thermomechanical Processing on Hydrogen Embrittlement Properties of UltraHigh-Strength TRIP-Aided Bainitic Ferrite Steels
by Tomohiko Hojo, Yutao Zhou, Junya Kobayashi, Koh-ichi Sugimoto, Yoshito Takemoto, Akihiko Nagasaka, Motomichi Koyama, Saya Ajito and Eiji Akiyama
Metals 2022, 12(2), 269; https://doi.org/10.3390/met12020269 - 31 Jan 2022
Cited by 1 | Viewed by 2156
Abstract
The effects of thermomechanical processing on the microstructure and hydrogen embrittlement properties of ultrahigh-strength, low-alloy, transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steels were investigated to apply to automobile forging parts such as engine and drivetrain parts. The hydrogen embrittlement properties were evaluated by [...] Read more.
The effects of thermomechanical processing on the microstructure and hydrogen embrittlement properties of ultrahigh-strength, low-alloy, transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steels were investigated to apply to automobile forging parts such as engine and drivetrain parts. The hydrogen embrittlement properties were evaluated by conducting conventional tensile tests after hydrogen charging and constant load four-point bending tests with hydrogen charging. The 0.4 mass%C-TBF steel achieved refinement of the microstructure, improved retained austenite characteristics, and strengthening, owing to thermomechanical processing. This might be attributed to dynamic and static recrystallizations during thermomechanical processing in TBF steels. Moreover, the hydrogen embrittlement resistances were improved by the thermomechanical processing in TBF steels. This might be caused by the refinement of the microstructure, an increase in the stability of the retained austenite, and low hydrogen absorption of the thermomechanically processed TBF steels. Full article
(This article belongs to the Special Issue Mechanical Properties and Microstructure of Forged Steel)
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17 pages, 3815 KiB  
Article
Gallic Acid as a Potential Green Corrosion Inhibitor for Aluminum in Acidic Solution
by Przemysław Kwolek, Kamil Dychtoń, Barbara Kościelniak, Andrzej Obłój, Agnieszka Podborska and Marek Wojnicki
Metals 2022, 12(2), 250; https://doi.org/10.3390/met12020250 - 28 Jan 2022
Cited by 10 | Viewed by 3109
Abstract
Plant extracts are intensively studied as green corrosion inhibitors of aluminum. Because these extracts are complex systems, the influence of their individual constituents on the corrosion of aluminum should be determined. In this work, gallic acid was tested for the first time as [...] Read more.
Plant extracts are intensively studied as green corrosion inhibitors of aluminum. Because these extracts are complex systems, the influence of their individual constituents on the corrosion of aluminum should be determined. In this work, gallic acid was tested for the first time as a corrosion inhibitor of aluminum in orthophosphoric acid aqueous solution. So far, its potential inhibiting properties in acidic solutions were only suggested based on promising results obtained for various plant extracts. Evaluation of the potential inhibiting properties of gallic acid was performed using electrochemical methods. The corrosion potential, polarization curves, and impedance spectra of aluminum in 0.5 M orthophosphoric acid, at T = 303 K, were determined. The corrosion potential, corrosion current density, and corrosion rate of aluminum in orthophosphoric acid were equal to −1.151 V vs. Ag|AgCl (3M KCl) reference electrode, 36 μA∙cm−2 and 0.39 mm∙year−1, respectively. These values did not change with the addition of gallic acid. The results obtained show that gallic acid does not inhibit aluminum corrosion. UV-Vis absorption spectra of gallic acid solutions and quantum mechanical calculations show that this organic compound did not adsorb onto the aluminum surface under the studied conditions. Full article
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10 pages, 11230 KiB  
Perspective
A Prospective Way to Achieve Ballistic Impact Resistance of Lightweight Magnesium Alloys
by Abdul Malik, Faisal Nazeer and Yangwei Wang
Metals 2022, 12(2), 241; https://doi.org/10.3390/met12020241 - 27 Jan 2022
Cited by 8 | Viewed by 2330
Abstract
The ballistic impact resistance of lightweight magnesium alloys is an eye-catching material for the military and aerospace industries, which can decrease the cost of a project and the fuel consumption. The shockwave mitigation ability of a magnesium alloy is 100 times stronger than [...] Read more.
The ballistic impact resistance of lightweight magnesium alloys is an eye-catching material for the military and aerospace industries, which can decrease the cost of a project and the fuel consumption. The shockwave mitigation ability of a magnesium alloy is 100 times stronger than an aluminum alloy; nonetheless, ballistic impact resistance has still not been achieved against blunt and API projectiles. The major obstacles are the low hardness, low mechanical strength, basal texture and strain hardening ability under loading along the normal direction of the sheet. The high yield strength and ultimate strength can be achieved for a specific loading condition (tensile or compression) by adjusting the texture in magnesium alloys. The projectile impact along the normal direction in a strong basal-textured magnesium alloy can only produce a slip-induced deformation or minor twinning activity. Here, we propose a practical technique that can be valuable for altering the texture from c-axes//ND to c-axes//ED or TD, and can produce high strain hardening and high strength through a twinning and de-twinning activity. Subsequently, it can improve the ballistic impact resistance of magnesium alloys. The effect of the technique on the evolution of the microstructure and possible anticipated deformation mechanisms after ballistic impact is proposed and discussed. Full article
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24 pages, 14256 KiB  
Article
Structural and Tribological Studies of “(TiC + WC)/Hardened Steel” PMMC Coating Deposited by Air Pulsed Plasma
by Yuliia Chabak, Vasily Efremenko, Vadym Zurnadzhy, Viktor Puchý, Ivan Petryshynets, Bohdan Efremenko, Victor Fedun, Kazumichi Shimizu, Iurii Bogomol, Volodymyr Kulyk and Dagmar Jakubéczyová
Metals 2022, 12(2), 218; https://doi.org/10.3390/met12020218 - 24 Jan 2022
Cited by 17 | Viewed by 2938
Abstract
The deposition of a thin (several tens of microns) protective coating in atmospheric conditions is a challenging task for surface engineering. The structural features and tribological properties of a particle-reinforced metal matrix composite coating synthesized on middle-carbon steel by air pulse-plasma treatments were [...] Read more.
The deposition of a thin (several tens of microns) protective coating in atmospheric conditions is a challenging task for surface engineering. The structural features and tribological properties of a particle-reinforced metal matrix composite coating synthesized on middle-carbon steel by air pulse-plasma treatments were studied in the present work. The 24–31 µm thick coating of “24 vol.% (TiC + WC)/Hardened steel matrix” was produced by 10 plasma pulses generated by an electro-thermal axial plasma accelerator equipped with a consumable cathode of novel design (low-carbon steel tube filled with “TiC/WC + Epoxy resin” mixture). The study included optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD, microhardness measurements, and dry “Ball-on-Plate” testing. The carbides were directly plasma-transferred to the substrate (steel of AISI 4145H grade) from the cathode without substantial melting. The hard (500–1044 HV) coating matrix consisted of 57 vol.% austenite (1.43 wt.% C) and 43 vol.% plate martensite was formed via carbon enrichment of steel from plasma flow. Additionally, a minor amount of oxide phases (TiO2, WO2, WO3) were dispersed in the matrix. As compared to substrate, the coating had a lower coefficient of friction; its volumetric wear was decreased by 4.4 times when sliding against hardened steel ball and by 16 times when sliding against SiC ball. Full article
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15 pages, 10670 KiB  
Article
The Microstructure and Mechanical Properties of 5083, 6005A and 7N01 Aluminum Alloy Gas Metal Arc-Welded Joints for High-Speed Train: A Comparative Study
by Laijun Wu, Biao Yang, Xiaohui Han, Guolong Ma, Bingxiao Xu, Yuhang Liu, Xiaoguo Song and Caiwang Tan
Metals 2022, 12(2), 213; https://doi.org/10.3390/met12020213 - 24 Jan 2022
Cited by 17 | Viewed by 4022
Abstract
This study aimed to conduct a comparative study on the microstructure and mechanical performance of 5083, 6005A and 7N01 Al joints used in China Railway High-speed (CRH) trains. We connected 10 mm-thick plates by three-layer and three-pass gas metal arc welding (GMAW). The [...] Read more.
This study aimed to conduct a comparative study on the microstructure and mechanical performance of 5083, 6005A and 7N01 Al joints used in China Railway High-speed (CRH) trains. We connected 10 mm-thick plates by three-layer and three-pass gas metal arc welding (GMAW). The results indicated that 6005A and 7N01 Al joints were more sensitive to grain boundary liquation in the partially melted zone (PMZ) than 5083 Al joins. Besides, recrystallization was obtained in heat-affected zones (HAZ). The 5083 Al joints experienced the most severe recrystallization and the grain size changed from 6.32 (BM) to 32.44 (HAZ) μm duo to intracrystalline strain induced by cold-rolled processes. The 7N01 Al alloys experienced the lowest extent of recrystallization and the grain size increased from 5.32 (BM) to 22.31 (HAZ) μm. Furthermore, significant precipitate evolution in the HAZ was observed. Original thin β” precipitates dissolved in HAZ of 6005A Al joints and transformed to the softer β phase. However, less precipitation transition was examined in 5083 and 7N01 Al joints. The precipitates’ evolution produced a softening region in HAZ of 6005A joints where the hardness was only 55 HV. The microhardness profile of the other two Al joints was less affected. The tensile strength of 5083, 6005A, and 7N01 Al alloy joints reached 323, 206 and 361 MPa, respectively. The 5083 Al and 6005A Al joints failed at HAZ near the fusion line while 7N01 Al joints failed at the fusion zone owing to the high strength of the base metal. The liquation, coarse grains by recrystallization, and precipitate evolution all decreased local strength, resulting in the fracture at HAZ. Full article
(This article belongs to the Special Issue Advanced Welding Technology in Metals II)
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15 pages, 1232 KiB  
Review
Viewpoints on Technological Aspects of Advanced High-Strength Bainitic Steels
by Lucia Morales-Rivas
Metals 2022, 12(2), 195; https://doi.org/10.3390/met12020195 - 21 Jan 2022
Cited by 7 | Viewed by 2954
Abstract
The development of advanced high-strength bainitic steels has been preceded and linked to different metallurgical advances, both in the field of fundamental materials science and in technological fields closer to the production and final application. The diversity and abundance of documents in literature [...] Read more.
The development of advanced high-strength bainitic steels has been preceded and linked to different metallurgical advances, both in the field of fundamental materials science and in technological fields closer to the production and final application. The diversity and abundance of documents in literature has favored the co-existence of extensive terminology in the context of advanced high-strength steels and bainitic steels. In this work, the concept of advanced high-strength bainitic steels is briefly revisited from a wide perspective, with the aim of highlighting the main limitations and challenges for further development of these microstructures. Full article
(This article belongs to the Special Issue Advanced High-Strength Bainitic Steels)
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12 pages, 6292 KiB  
Article
Performance of a Nozzle to Control Bath Level Oscillations and Turbulence of the Metal-Flux Interface in Slab Molds
by María Guadalupe González-Solórzano, Rodolfo Davila Morales, Javier Guarneros, Carlos Rodrigo Muñiz-Valdés and Alfonso Nájera Bastida
Metals 2022, 12(1), 140; https://doi.org/10.3390/met12010140 - 12 Jan 2022
Cited by 3 | Viewed by 1574
Abstract
The characterization of the turbulent flow of liquid steel in a slab mold using a commercial nozzle was carried out through physical experiments and mathematical models. Six ultrasonic sensors were located at each side of the nozzle to obtain real-time plotting of the [...] Read more.
The characterization of the turbulent flow of liquid steel in a slab mold using a commercial nozzle was carried out through physical experiments and mathematical models. Six ultrasonic sensors were located at each side of the nozzle to obtain real-time plotting of the bath levels during the experimental time. An ultrasonic transducer located in the mold, 20 mm below the meniscus, determines the velocities and the turbulent variables along with the distance from the narrow face to the position of the nozzle’s outer wall. These data, together with the mathematical simulations, demonstrated a high correlation of bath level oscillations and the time-dependent behavior of the discharging jets. The flow inside the mold shows low-frequency non-symmetric patterns without a severe turbulent in the meniscus. The source of this instability is the partial opening of the slide valve gate used to control the mass flow of liquid. Full article
(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)
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17 pages, 8878 KiB  
Article
The Research on Recrystallization Behaviors and Mechanism of a Medium-Density Ni-Based Alloy
by Kai Feng, Xiaxu Huang, Rui Wang, Wenli Xue, Yilei Fu and Zhaoxin Li
Metals 2022, 12(1), 137; https://doi.org/10.3390/met12010137 - 11 Jan 2022
Viewed by 1837
Abstract
Revealing the recrystallization behavior and mechanism of this new alloy is of great significance to subsequent research. In this study, the Ni-36.6W-15Co ternary medium heavy alloy was solution-treated at 1100–1200 °C for different lengths of time. The grain size change, microstructure and texture [...] Read more.
Revealing the recrystallization behavior and mechanism of this new alloy is of great significance to subsequent research. In this study, the Ni-36.6W-15Co ternary medium heavy alloy was solution-treated at 1100–1200 °C for different lengths of time. The grain size change, microstructure and texture evolution as well as twin development during recrystallization annealing were analyzed using SEM, EBSD and TEM techniques. The study found that complete recrystallization occurs at 1150 °C/60 min. In addition, it takes a longer amount of time for complete recrystallization to occur at 1100 °C. The value of the activation energy Q1 of the studied alloys is 701 kJ/mol and the recrystallization process is relatively slow. By comparing the changes of microstructure and texture with superalloys, it is found that the recrystallization mechanism of the studied alloy is different from that of the superalloy. The development of annealing twins has a great influence on the recrystallization behavior and mechanism. The results show that the twin mechanism is considered as the dominant recrystallization mechanism of the studied alloy, although the formation and development of sub-grains appear in the early stage of recrystallization. Full article
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46 pages, 6639 KiB  
Review
Recent Developments and Future Challenges in Incremental Sheet Forming of Aluminium and Aluminium Alloy Sheets
by Tomasz Trzepieciński, Sherwan Mohammed Najm, Valentin Oleksik, Delia Vasilca, Imre Paniti and Marcin Szpunar
Metals 2022, 12(1), 124; https://doi.org/10.3390/met12010124 - 09 Jan 2022
Cited by 22 | Viewed by 4988
Abstract
Due to a favourable strength-to-density ratio, aluminium and its alloys are increasingly used in the automotive, aviation and space industries for the fabrication of skins and other structural elements. This article explores the opportunities for and limitations of using Single- and Two Point [...] Read more.
Due to a favourable strength-to-density ratio, aluminium and its alloys are increasingly used in the automotive, aviation and space industries for the fabrication of skins and other structural elements. This article explores the opportunities for and limitations of using Single- and Two Point Incremental Sheet Forming techniques to form sheets from aluminium and its alloys. Incremental Sheet Forming (ISF) methods are designed to increase the efficiency of processing in low- and medium-batch production because (i) it does not require the production of a matrix and (ii) the forming time is much higher than in conventional methods of sheet metal forming. The tool in the form of a rotating mandrel gradually sinks into the sheet, thus leading to an increase in the degree of deformation of the material. This article provides an overview of the published results of research on the influence of the parameters of the ISF process (feed rate, tool rotational speed, step size), tool path strategy, friction conditions and process temperature on the formability and surface quality of the workpieces. This study summarises the latest development trends in experimental research on, and computer simulation using, the finite element method of ISF processes conducted in cold forming conditions and at elevated temperature. Possible directions for further research are also identified. Full article
(This article belongs to the Special Issue Challenges and Achievements in Metal Forming)
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11 pages, 8506 KiB  
Article
Transmission Electron Microscopy Study on the Precipitation Behaviors of Laser-Welded Ferritic Stainless Steels and Their Implications on Intergranular Corrosion Resistance
by Niklas Sommer, Clementine Warres, Tarek Lutz, Martin Kahlmeyer and Stefan Böhm
Metals