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Volume 15
Issue 10
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Metals, Volume 15, Issue 10 (October 2025) – 104 articles

Cover Story (view full-size image): Pouring of metals during casting creates dense populations of cracks in the liquid, which survive in the solid. The cracks, called bifilms, are casting defects from the folding of oxide films. Although they are mainly invisible, they can play a major role in the failure of metals. The cracks are generally closed but become more serious if opened by the precipitation of a second phase, such as carbides in steels. Failure modes of stress corrosion cracking, hydrogen embrittlement and hydrogen cracking are now enhanced. Revised casting methods can eliminate bifilms and these failure modes. View this paper
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29 pages, 8000 KB  
Review
Enhancing Biomedical Metal 3D Printing with AI and Nanomaterials Integration
by Jackie Liu, Jaison Jeevanandam and Michael K. Danquah
Metals 2025, 15(10), 1163; https://doi.org/10.3390/met15101163 - 21 Oct 2025
Viewed by 107
Abstract
The integration of artificial intelligence (AI) with nanomaterials is rapidly transforming metal three-dimensional (3D) printing for biomedical applications due to their unprecedented precision, customization, and functionality. This article discusses the role of AI in optimizing design parameters, predicting material behaviors, and controlling additive [...] Read more.
The integration of artificial intelligence (AI) with nanomaterials is rapidly transforming metal three-dimensional (3D) printing for biomedical applications due to their unprecedented precision, customization, and functionality. This article discusses the role of AI in optimizing design parameters, predicting material behaviors, and controlling additive manufacturing processes for metal-based implants and prosthetics. Nanomaterials, particularly metallic nanoparticles, enhance the mechanical strength, biocompatibility, and functional properties of 3D-printed structures. AI-driven models, including machine learning (ML) and deep learning algorithms, are increasingly used to forecast print quality, detect defects in real-time, and reduce material waste. Moreover, data-driven design approaches enable patient-specific implant development and predictive modeling of biological responses. We highlight recent advancements in AI-guided material discovery through microstructure–property correlations and multi-scale simulation. Challenges such as data scarcity, standardization, and integration across interdisciplinary domains are also discussed, along with emerging solutions based on federated learning and the digital twinning approach. Further, the article emphasizes the importance of AI and nanomaterials to revolutionize metal 3D printing to fabricate smarter, safer, and effective biomedical devices. Future perspectives covering the need for robust datasets, explainable AI frameworks, and regulatory frameworks to ensure the clinical translation of AI-enhanced additive manufacturing technologies are discussed. Full article
(This article belongs to the Special Issue Metal 3D Printing Techniques for Biomedical Applications)
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15 pages, 2781 KB  
Article
Sodium Percarbonate for Eco-Efficient Cyanide Detoxification in Gold Mining Tailings
by Ainur Berkinbayeva, Shynar Saulebekkyzy, Bagdaulet Kenzhaliyev, Kenzhegali Smailov, Azamat Yessengaziyev, Nargiza Nurtazina, Diana Karim and Yerkem Birlikzhan
Metals 2025, 15(10), 1162; https://doi.org/10.3390/met15101162 - 21 Oct 2025
Viewed by 75
Abstract
Cyanide-containing effluents from hydrometallurgical gold extraction pose significant environmental risks due to their high toxicity. This study investigates the detoxification of cyanide-laden tailings from the Altyntau Kokshetau gold extraction facility (Kazakhstan) using sodium percarbonate in alkaline conditions. Employing response surface methodology (RSM) and [...] Read more.
Cyanide-containing effluents from hydrometallurgical gold extraction pose significant environmental risks due to their high toxicity. This study investigates the detoxification of cyanide-laden tailings from the Altyntau Kokshetau gold extraction facility (Kazakhstan) using sodium percarbonate in alkaline conditions. Employing response surface methodology (RSM) and central composite design (CCD), we optimized key parameters—pH (10–12), sodium percarbonate dosage (1.5–4.0 g), reaction time (10–40 min) and temperature (20–25 °C)—achieving 83.33% detoxification efficiency within 40 min and 99.99% after 8 h, reducing cyanide from 443.2 mg/L to 0.05 mg/L. The process follows biphasic pseudo-first-order kinetics ((k1 = 0.0517) min–1 initially, (k2 = 0.01665) min–1 subsequently), driven by HO• radical-mediated oxidation of CN− to CNO−, as described by (CN−+H2O2→CNO−+ H2O). pH emerged as the dominant factor, optimizing radical stability and CN− protonation (pKa ≈ 9.21) at pH 10. Infrared spectroscopy confirmed the presence of cyanide complexes ([Au(CN)2]−, [Fe(CN)6]4−) in tailings, underscoring the need for effective treatment. The method ensures compliance with stringent environmental standards (e.g., ICMI limit of 0.2 mg/L), offering a scalable, eco-efficient solution for mitigating the environmental footprint of gold mining operations. Full article
(This article belongs to the Special Issue Advances in Mineral Processing and Hydrometallurgy—4th Edition)
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19 pages, 4904 KB  
Article
Room-Temperature Superplasticity in a Biodegradable Zn-0.1Mg Alloy
by Karel Saksl, Róbert Kočiško, Patrik Petroušek, Miloš Matvija, Martin Fujda, Dávid Csík, Zuzana Molčanová, Beáta Ballóková, Iryna Cuperová, Katarína Gáborová, Maksym Lisnichuk, Miloslav Lupták and Adam Lupták
Metals 2025, 15(10), 1161; https://doi.org/10.3390/met15101161 - 21 Oct 2025
Viewed by 86
Abstract
Biodegradable zinc-based alloys have recently emerged as promising candidates for temporary biomedical implants due to their favorable biocompatibility, appropriate degradation rate, and relatively simple processing. In this study, the Zn-0.1Mg alloy was investigated after being processed by means of a two-step equal-channel angular [...] Read more.
Biodegradable zinc-based alloys have recently emerged as promising candidates for temporary biomedical implants due to their favorable biocompatibility, appropriate degradation rate, and relatively simple processing. In this study, the Zn-0.1Mg alloy was investigated after being processed by means of a two-step equal-channel angular pressing (ECAP) route, consisting of the first pass at 150 °C followed by a second pass at room temperature. The mechanical properties were evaluated using uniaxial tensile tests at different strain rates, while the microstructure and phase composition were analyzed using synchrotron hard X-ray diffraction and transmission electron microscopy (TEM). The processed alloy exhibited a remarkable enhancement in both strength and ductility compared to the annealed state. At the lowest applied strain rate, a fracture elongation of up to 240% was achieved at room temperature, representing a unique manifestation of superplasticity under ambient conditions. Diffraction analysis confirmed the stability of the supersaturated Zn matrix with minor Mg2Zn11 intermetallic phase. TEM observations revealed an ultrafine-grained microstructure and activation of non-basal slip systems, which enabled efficient plastic flow. These findings demonstrate that controlled severe plastic deformation provides an effective pathway for tailoring Zn-Mg alloys, opening opportunities for their use in the next generation of bioresorbable low-to-moderate load orthopedic fixation devices, e.g., plates, screws, suture anchors and craniofacial miniplates. Full article
(This article belongs to the Special Issue The Forming Behaviour and Plasticity of Metallic Alloys)
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13 pages, 2414 KB  
Article
The Rapid Catalytic Degradation of Reactive Black 5 Using Mo51Fe34B15 Metallic Glass Wire
by Ya-Nan Chen, Bo Song, Chengquan Zhang, Tao Li, Chen Su and Shengfeng Guo
Metals 2025, 15(10), 1160; https://doi.org/10.3390/met15101160 - 21 Oct 2025
Viewed by 79
Abstract
Metallic glass, as an emerging catalytic material, possesses an atomic structure characterized by long-range disorder and short-range order, which creates abundant and accessible active sites that enhance the adsorption and reactivity toward pollutant molecules, particularly dye compounds. In treating highly colored and recalcitrant [...] Read more.
Metallic glass, as an emerging catalytic material, possesses an atomic structure characterized by long-range disorder and short-range order, which creates abundant and accessible active sites that enhance the adsorption and reactivity toward pollutant molecules, particularly dye compounds. In treating highly colored and recalcitrant Reactive Black 5 (RB5) dye wastewater, Mo51Fe34B15 metallic glass wire demonstrate outstanding catalytic degradation performance within a conventional Fenton-like system. Under acidic conditions (pH = 2), the material exhibits a degradation rate constant of 0.698 min−1 for a 20 ppm RB5 dye solution, achieving a degradation efficiency of 98.8% within 10 min. After 10 consecutive cycles, the efficiency remains at 95%, and throughout 15 cycles, it consistently maintains a performance level above 90%. As the reaction proceeds, the degradation rate gradually decreases, primarily due to the accumulation of corrosion products on the catalyst surface, which are predominantly composed of MoO3 and Fe2O3. During the degradation process, metallic Mo0 and Fe0 serve as electron donors that facilitate the decomposition of H2O2, generating highly reactive hydroxyl radicals (•OH). These radicals attack the chromophoric structure of the dye, leading to its structural disruption and enabling rapid decolorization. Full article
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15 pages, 6679 KB  
Article
Formation and Characterization of Ti-Al Intermetallic and Oxide Layers on Ti6Al4V as Interlayers for Hydroxyapatite Coatings
by Stefan Alexandru Laptoiu, Marian Miculescu, Diana Enescu, Iulian Antoniac and Florin Miculescu
Metals 2025, 15(10), 1159; https://doi.org/10.3390/met15101159 - 21 Oct 2025
Viewed by 169
Abstract
This study explores a novel approach to enhance the surface properties of Ti-Al alloys for biomedical applications by creating a compositional gradient layer through aluminum deposition using Electrical Discharge Machining (EDM). The primary goal was to develop a metallurgically bonded intermetallic zone that [...] Read more.
This study explores a novel approach to enhance the surface properties of Ti-Al alloys for biomedical applications by creating a compositional gradient layer through aluminum deposition using Electrical Discharge Machining (EDM). The primary goal was to develop a metallurgically bonded intermetallic zone that supports strong adhesion and improved compatibility for subsequent hydroxyapatite (HA) deposition. Aluminum was deposited onto a Ti6Al4V substrate via EDM under controlled conditions, followed by thermal and thermochemical treatments to induce diffusion and intermetallic phase formation. Comprehensive analyses using optical and electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) revealed the formation of well-adhered layers composed of complex Ti-Al intermetallics such as TiAl2 and TiAl3, along with oxide phases including TiO2 and Al2O3. Thermal and thermochemical treatments further improved surface hardness, reaching up to 1057 HV, and influenced the diffusion behavior of aluminum, titanium, and vanadium. Adhesion tests confirmed that the untreated and thermochemically treated layers exhibited superior mechanical stability, while thermal treatment alone led to brittleness and delamination. These findings demonstrate that a properly engineered intermediate aluminide layer can significantly improve the performance of bioceramic coatings, particularly HA, by providing enhanced structural integrity and biocompatibility. Full article
(This article belongs to the Special Issue Light Alloy and Its Application (3rd Edition))
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13 pages, 1700 KB  
Article
Investigation into Hot Deformation Behavior and Processing Maps of 14CrMoR High-Performance Vessel Steel
by Ya Gao, Yuzhuo Zhao, Yuan Gao, Zejin Chen, Yangbing Li, Weina Zhang and Zhenyu Liu
Metals 2025, 15(10), 1158; https://doi.org/10.3390/met15101158 - 20 Oct 2025
Viewed by 115
Abstract
14CrMoR steel, possessing excellent low-temperature impact toughness and corrosion resistance, is an important material for core equipment in the coal chemical industry. In this paper, 14CrMoR steel was subjected to single-pass compression tests at deformation temperatures ranging from 900 to 1150 °C and [...] Read more.
14CrMoR steel, possessing excellent low-temperature impact toughness and corrosion resistance, is an important material for core equipment in the coal chemical industry. In this paper, 14CrMoR steel was subjected to single-pass compression tests at deformation temperatures ranging from 900 to 1150 °C and strain rates of 0.1, 1, 5, and 10 s−1. The hot deformation behavior and constitutive relationship were investigated. The strain rate sensitivity factor m, power dissipation coefficient η, and instability parameter ξ were calculated, respectively. A power dissipation map was plotted, and a hot processing map was established. The results showed that the stress of 14CrMoR steel increased with the decrease in deformation temperature and the increase in strain rate. Dynamic recrystallization was likely to occur at high deformation temperatures and low strain rates. When the strain rate was 10 s−1, in the temperature range of 900–950 °C, the power dissipation rate was the lowest. With the increase in temperature, the power dissipation rate rose, and the maximum power dissipation rate was reached in the temperature range of 1100–1150 °C. The research on the hot deformation behavior of 14CrMoR steel has important guiding significance for the design and optimization of the process. Full article
(This article belongs to the Special Issue Research on Microstructure and Performance Mechanisms of Advanced Steels and Alloys)
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22 pages, 5578 KB  
Article
Effect of Hot Rolling on the Microstructure and Properties of Dispersion-Strengthened W-La Alloy
by Junling Fan, Tianlin Zhu, Jun Cao, Yongzhen Sun and Junchao Zhang
Metals 2025, 15(10), 1157; https://doi.org/10.3390/met15101157 - 20 Oct 2025
Viewed by 127
Abstract
The effects of different deformation processing routes (rolling and rotary forging) and temperature conditions on the microstructure and mechanical properties of W-1%La2O3 alloy wire were investigated. The results indicate that with increasing cumulative deformation (from ø22 mm to ø5.2 mm), [...] Read more.
The effects of different deformation processing routes (rolling and rotary forging) and temperature conditions on the microstructure and mechanical properties of W-1%La2O3 alloy wire were investigated. The results indicate that with increasing cumulative deformation (from ø22 mm to ø5.2 mm), the grain refinement efficiency of the “rolling + rotary forging” sequence is significantly superior to that of the “rotary forging + rotary forging” process. For the as-deformed ø5.2 mm W-La alloy bars, the material processed by “rolling + rotary forging” exhibited a higher Vickers hardness of 544.9 HV compared to that processed solely by rotary forging. Following annealing treatment, the hardness values of ø9.0 mm and ø5.2 mm bars produced via the “rolling + rotary forging” route were 467.2 HV and 460.4 HV, respectively. These values are notably higher than those obtained from the “rotary forging + rotary forging” process, which measured 446.1 HV and 433.5 HV for the corresponding diameters. In summary, this study systematically compares the effects of rolling and rotary forging processes on the microstructure and properties of W-La alloy, providing a valuable foundation for the future development of high-strength tungsten alloy wires. Full article
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5 pages, 200 KB  
Editorial
Microstructure and Properties in Metals and Alloys (Volume 3)
by Andrea Di Schino, Claudio Testani and Robert Bidulský
Metals 2025, 15(10), 1156; https://doi.org/10.3390/met15101156 (registering DOI) - 20 Oct 2025
Viewed by 177
Abstract
Microstructure design is a main issue when targeting a target material’s properties [...] Full article
(This article belongs to the Topic Microstructure and Properties in Metals and Alloys, 3rd Volume)
18 pages, 1471 KB  
Article
The Leaching of Valuable Metals (Li, Co, Ni, Mn, Cu) from Black Mass from Spent Lithium-Ion Batteries
by Rorie Gilligan, Glen P. O’Malley and Aleksandar N. Nikoloski
Metals 2025, 15(10), 1155; https://doi.org/10.3390/met15101155 - 19 Oct 2025
Viewed by 610
Abstract
Near-complete (>99%) dissolution of lithium and cobalt was achieved by the leaching of black mass from spent (end-of-life) lithium-ion batteries (LiBs) using 4 M H2SO4 or HCl at 60 °C. Raising the temperature to 90 °C did not increase the [...] Read more.
Near-complete (>99%) dissolution of lithium and cobalt was achieved by the leaching of black mass from spent (end-of-life) lithium-ion batteries (LiBs) using 4 M H2SO4 or HCl at 60 °C. Raising the temperature to 90 °C did not increase the overall extraction of lithium or cobalt, but it increased the rate of extraction. At 60 °C, 2 M H2SO4 or 2 M HCl performed similarly to the 4 M H2SO4/HCl solution, although extractions were lower using 1 M H2SO4 or HCl (~95% and 98%, respectively). High extractions were also observed by leaching in low pulp density (15 g/L) at 60 °C with 2 M CH2ClCOOH. Leaching was much slower with hydrogen peroxide reductant concentrations below 0.5 mol/L, with cobalt extractions of 90–95% after 3 h. Pulp densities of up to 250 g/L were tested when leaching with 4 M H2SO4 or HCl, with the stoichiometric limit estimated for each test based on the metal content of the black mass. Extractions were consistently high, above 95% for Li/Ni/Mn/Cu with a pulp density of 150 g/L, dropping sharply above this point because of insufficient remaining acid in the solution in the later stages of leaching. The final component of the test work used leaching parameters identified in the previous experiments as producing the largest extractions, and just sulphuric acid. A seven-stage semi-continuous sulphuric acid leach at 60 °C of black mass from LiBs that had undergone an oxidising roast (2h in a tube furnace at 500 °C under flowing air) to remove binder material resulted in high (93%) extraction of cobalt and near total (98–100%) extractions of lithium, nickel, manganese, and copper. Higher cobalt extraction (>98%) was expected, but a refractory spinel-type cobalt oxide, Co3O4, was generated during the oxidising roast as a result of inefficient aeration, which reduced the extraction efficiency. Full article
(This article belongs to the Special Issue Cutting-Edge Innovations in Metal Recovery from Electronic Waste: Challenges, Techniques and Future Horizons)
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21 pages, 3808 KB  
Article
Novel Approach to the Surface Degradation Assessment of 42CrMo4 Steel in Marine and Cavitation Erosion Environments
by Stanica Nedović, Ana Alil, Sanja Martinović, Stefan Dikić, Dragomir Glišić and Tatjana Volkov-Husović
Metals 2025, 15(10), 1154; https://doi.org/10.3390/met15101154 - 17 Oct 2025
Viewed by 345
Abstract
This study focuses on the susceptibility and surface degradation of low-alloy carbon steel 42CrMo4 to corrosion and cavitation erosion, as this steel is widely used in marine environments with aggressive chemical species and harsh conditions. Due to its high strength and fatigue resistance, [...] Read more.
This study focuses on the susceptibility and surface degradation of low-alloy carbon steel 42CrMo4 to corrosion and cavitation erosion, as this steel is widely used in marine environments with aggressive chemical species and harsh conditions. Due to its high strength and fatigue resistance, 42CrMo4 steel is often employed in offshore mechanical components such as shafts and fasteners as well as crane parts in ports and harbors. Various experimental methods, including corrosion and cavitation tests, were used to assess the steel’s surface integrity under extreme conditions. Surface changes were monitored using modern analytical tools for precise assessments, including image and morphological analyses, to quantify degradation levels and specific parameters of defects induced by corrosion and cavitation. Non-destructive techniques such as optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and image analysis software were employed for the quantitative assessment of morphological parameters and elemental analysis. EDS analysis revealed changes in elemental composition, indicating corrosion products that caused significant mass loss and defect formation, with degradation increasing over time. The average corrosion rate of 42CrMo4 steel in a 3.5% NaCl solution reached a peak value of 0.846 mm/year after 120 days of exposure. Cavitation erosion behavior was measured based on mass loss, indicating the occurrence of different cavitation periods, with the steady-state period achieved after 60 min. The number of formed pits increased until 120 min, after which it decreased slightly. This indicates that a time frame of 120 min was identified as significant for changes in the mechanism of pit formation. Specifically, up to 120 min, pit formation was the dominant mechanism of cavitation erosion, while after that, as the number of pits slightly declined, the growth and merging of formed pits became the dominant mechanism. The cavitation erosion tests showed mass loss and mechanical damage, characterized by the formation of pits and cavities. The findings indicate that the levels of surface degradation were higher for corrosion than for cavitation. The presented approach also provides an assessment of the degradation mechanisms of 42CrMo4 steel exposed to corrosive and cavitation conditions. Full article
(This article belongs to the Special Issue Feature Paper Collection of “Current Challenges in Corrosion Research" (2nd Edition))
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16 pages, 6535 KB  
Article
Effect of Overlap Rate on Microstructure and Corrosion Behavior of Laser-Clad Ni60-WC Composite Coatings on E690 Steel
by Yupeng Cao, Guicang Guo, Ming Qiu, Rui Zhou and Jiaxin Qin
Metals 2025, 15(10), 1153; https://doi.org/10.3390/met15101153 - 17 Oct 2025
Viewed by 203
Abstract
To investigate the influence of laser cladding overlap rate on the microstructure and corrosion resistance of cladded layers, Ni60-WC composite coatings with different overlap rates (30%, 50%, and 70%) were prepared on E690 offshore steel in this study. The relationship between the corrosion [...] Read more.
To investigate the influence of laser cladding overlap rate on the microstructure and corrosion resistance of cladded layers, Ni60-WC composite coatings with different overlap rates (30%, 50%, and 70%) were prepared on E690 offshore steel in this study. The relationship between the corrosion resistance and microstructure of the cladded layers fabricated at different overlap rates was analyzed using an electrochemical workstation, scanning electron microscope, X-ray diffractometer, and energy dispersive spectrometer. The results demonstrate that the overlap rate exerts a significant impact on the corrosion resistance of the cladded layers, and the corrosion resistance of the cladded layers gradually improves with the increase in overlap rate. The cladded layer prepared with a 70% overlap rate exhibits excellent corrosion resistance, featuring the highest open-circuit potential (−0.31 V vs. SCE), the lowest corrosion current density (3.35 μA/cm2), the largest capacitive arc radius in the electrochemical impedance spectroscopy (EIS), and a relatively flat surface after corrosion tests. Microstructural characterization results indicate that the increase in overlap rate promotes grain refinement and the formation of reinforcing phases (e.g., M23C6). The coating with a 70% overlap rate possesses the densest microstructure and abundant flocculent carbides, which act as an effective barrier against the penetration of corrosive media, thereby endowing it with optimal performance. Full article
(This article belongs to the Special Issue Fabricating Advanced Metallic Materials)
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16 pages, 8731 KB  
Article
Effect of Tempering Temperature on Carbide Evolution and Mechanical Response of Deep Cryogenically Treated Martensitic Stainless Steel
by Muhammad Rizqi Ramadhan Fatih, Hou-Jen Chen, Kun-Ming Lin and Hsin-Chih Lin
Metals 2025, 15(10), 1152; https://doi.org/10.3390/met15101152 - 17 Oct 2025
Viewed by 147
Abstract
Deep cryogenic treatment (DC) is widely applied to martensitic stainless steels to suppress the presence of metastable retained austenite (RA), which may otherwise transform into brittle martensite under deformation and degrade mechanical performance. In this study, a low-carbon 13Cr-2Ni-2Mo martensitic stainless steel was [...] Read more.
Deep cryogenic treatment (DC) is widely applied to martensitic stainless steels to suppress the presence of metastable retained austenite (RA), which may otherwise transform into brittle martensite under deformation and degrade mechanical performance. In this study, a low-carbon 13Cr-2Ni-2Mo martensitic stainless steel was subjected to deep cryogenic treatment for 2 h, followed by tempering at 200–600 °C to investigate carbide evolution and its correlation with mechanical response. At 200 °C, undissolved M23C6 was observed, accompanied by an RA volume fraction of 8.43% which exhibited a hardness of 543.3 ± 5.1 Hv. When tempered at 400 °C, M3C became predominant, corresponding to a hardness of 524.5 ± 5.1 Hv. At 500 °C, the simultaneous precipitation of M3C, M7C3, and M23C6 carbides induced pronounced secondary hardening, which promoted the peak hardness of 559 ± 5.6 Hv. Further tempering at 600 °C resulted in carbide spheroidization M23C6, which resulted in a hardness reduction to 392.2 ± 3.9 Hv while enhancing ductility. These findings reveal that the tempering temperature plays a decisive role in controlling the carbide precipitation sequence and the stability of retained austenite, thereby enabling the design of an optimal strength–ductility balance in deep cryogenically treated martensitic stainless steels. Full article
(This article belongs to the Special Issue Metallic Materials Behaviour Under Applied Load)
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37 pages, 6348 KB  
Article
Quantification of Austenite in Medium Manganese Steels Using the Magnetic Permeameter
by Hongqian Huang, Linxiu Du, Hongyan Wu and Xiuhua Gao
Metals 2025, 15(10), 1151; https://doi.org/10.3390/met15101151 - 17 Oct 2025
Viewed by 318
Abstract
With the industrial production and application of a series of advanced high-strength steels containing austenite phases, quantifying austenite content has become vital for optimizing production processes and guaranteeing product quality. Traditional austenite measurement methods typically demand laborious, meticulous sample preparation and complex subsequent [...] Read more.
With the industrial production and application of a series of advanced high-strength steels containing austenite phases, quantifying austenite content has become vital for optimizing production processes and guaranteeing product quality. Traditional austenite measurement methods typically demand laborious, meticulous sample preparation and complex subsequent data processing, rendering them unsuitable for large-scale industrial standardization. The industry urgently requires a simple, stable technique for determining austenite content in bulk samples of these advanced steels. This article explored an innovative permeameter method to achieve the simple and stable quantitative determination of the austenite content in multiphase steels. This method measures the magnetization data within the near-saturation range, then utilizes the linear Frölich–Kennelly relationship to fit the data and indirectly derive the saturation magnetization, and subsequently determines the austenite content. Using medium manganese steels with varied austenite fractions as experimental materials, we conducted cross-comparisons with conventional methods—using a vibrating sample magnetometer and X-ray diffraction—to rigorously demonstrate the method’s feasibility, accuracy, and reliability. Extensive experimental results confirm that this method is both feasible and sensitive, with the measurement error meeting industrial requirements for quantitative austenite determination. It offers significant advantages in operational simplicity, analysis efficiency, measurement stability, and sensitivity, making it particularly well-suited for the quantification of austenite in medium manganese steels. Full article
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16 pages, 2238 KB  
Article
High-Cycle Fatigue Strength Prediction Model for Ti-6Al-4V Titanium Alloy Compressor Blades Subjected to Foreign Object Damage
by Wangtian Yin, Yongbao Liu, Xing He and Zegang Tian
Metals 2025, 15(10), 1150; https://doi.org/10.3390/met15101150 - 17 Oct 2025
Viewed by 206
Abstract
The high-cycle fatigue (HCF) strength of titanium alloy blades, particularly Ti-6Al-4V, is critical for the reliability and performance of aviation engine components. Foreign object damage (FOD), which introduces notches, microstructural alterations, and residual stresses, significantly degrades the fatigue performance of these blades. Of [...] Read more.
The high-cycle fatigue (HCF) strength of titanium alloy blades, particularly Ti-6Al-4V, is critical for the reliability and performance of aviation engine components. Foreign object damage (FOD), which introduces notches, microstructural alterations, and residual stresses, significantly degrades the fatigue performance of these blades. Of particular concern are tensile residual stresses, which, caused by factors such as FOD, notches, or non-uniform plastic deformation, lead to increased local tensile loads, promote crack initiation, and accelerate crack growth. This study investigates the effects of external damage, including the impact angle and the resultant residual stresses, on the high-cycle fatigue strength of Ti-6Al-4V titanium alloy blades. Blade simulation specimens with impact-induced damage were tested under high-cycle fatigue conditions to assess the influence of various impact angles and the resulting tensile residual stresses. A modified fatigue strength prediction model was developed, incorporating shear factors and tensile residual stresses, to improve the accuracy of fatigue life predictions. Compared with the Neuber model and Peterson model, the modified model increases the proportion of predictions falling within the 10% scatter band by 30%, resulting in a significant improvement in prediction accuracy. The experimental results demonstrated that the modified model more accurately predicted the high-cycle fatigue strength, particularly in the presence of external damage and tensile residual stresses. Full article
(This article belongs to the Special Issue Advances in the Fatigue and Fracture Behaviour of Metallic Materials)
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17 pages, 5368 KB  
Article
Process and Dephosphorization Mechanism for Producing Low-Phosphorus Steel via Direct Reduction–Electric Furnace Smelting Separation of Alkaline Briquettes from Refractory High-Phosphorus Oolitic Magnetite Concentrate
by Mengjie Hu, Deqing Zhu, Jian Pan and Siwei Li
Metals 2025, 15(10), 1149; https://doi.org/10.3390/met15101149 - 17 Oct 2025
Viewed by 207
Abstract
High-phosphorus oolitic iron ores (HPOIOs) possess abundant reserves but are incompatible with conventional blast furnace ironmaking, as phosphorus migrates into hot metals during carbothermic reduction, preventing the production of low-phosphorus clean steel. To overcome this limitation, an innovative approach integrating alkaline briquette direct [...] Read more.
High-phosphorus oolitic iron ores (HPOIOs) possess abundant reserves but are incompatible with conventional blast furnace ironmaking, as phosphorus migrates into hot metals during carbothermic reduction, preventing the production of low-phosphorus clean steel. To overcome this limitation, an innovative approach integrating alkaline briquette direct reduction and smelting separation was proposed. Briquettes were prepared from oolitic magnetite concentrate (52.01 wt% Fe, 0.29 wt% P, 0.11 wt% S) with a basicity (R) of 2.0 and 5 wt% MgO added as a desulfurizer. After direct reduction and smelting separation, the resulting metallic iron exhibited a content of 98.56 wt% Fe, with 0.036 wt% P and 0.046 wt% S, achieving an Fe recovery of 87.63%. The dephosphorization and desulfurization efficiencies reached 94.67% and 90.56%, respectively, meeting the clean steel requirements. Phosphorus was effectively stabilized within the gehlenite and merwinite phases as a solid solution of Ca3(PO4)2, inhibiting its transfer to iron. Thermodynamic analyses confirmed that high basicity (R ≥ 2.0) significantly suppressed P2O5 activity, preventing phosphate reduction. The formation of a Ca3(PO4)2–Ca2SiO4 solid solution further obstructed phosphorus migration. This dual mechanism of “chemical fixation and thermodynamic stabilization” enables efficient dephosphorization, offering a sustainable pathway for utilizing HPOIOs. Full article
(This article belongs to the Special Issue Efficient Utilization of Metal Mineral Resources and Low-Carbon Metallurgy)
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23 pages, 36048 KB  
Article
Effects of Multi-Crack Initiation in High-Speed Railway Wheel Subsurface on Tread Peeling Lifetime
by Tao Guo, Bingzhi Chen and Xiuyang Fang
Metals 2025, 15(10), 1148; https://doi.org/10.3390/met15101148 - 16 Oct 2025
Viewed by 231
Abstract
The evolution characteristics of multi-source-fatigue-crack propagation in the subsurface of a high-speed wheel’s tread and its influence on tread peeling life are the basis for accurately evaluating wheel service lifetime. This study explores the influence of morphology distribution and the size of cracks [...] Read more.
The evolution characteristics of multi-source-fatigue-crack propagation in the subsurface of a high-speed wheel’s tread and its influence on tread peeling life are the basis for accurately evaluating wheel service lifetime. This study explores the influence of morphology distribution and the size of cracks in the tread on peeling life. The results show that the crack propagation mode in the wheel is mainly mode II and mode III composite propagation caused by shear stress. A fatigue crack inside the wheel with an angle of 45° represents the most dangerous situation. The maximum value of the von Mises stress inside the wheel increases with the increase in the number of multi-source cracks. The equivalent stress intensity factor (SIF) for multi-source cracks is higher than for a single crack. Also, mode III propagation has higher sensitivity to the number of cracks. The existence of multi-source cracks also increases the initial driving force ΔKeq of crack propagation. The results are useful for the evaluation of the service life of high-speed wheels. Full article
(This article belongs to the Special Issue Recent Advances in High-Performance Steel)
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22 pages, 175162 KB  
Article
A Test for Susceptibility to Solidification Cracking and Liquation Cracking in Additive Manufacturing
by Soumyadeep Dasgupta, Dan Thoma and Sindo Kou
Metals 2025, 15(10), 1147; https://doi.org/10.3390/met15101147 - 16 Oct 2025
Viewed by 265
Abstract
Solidification cracking and liquation cracking have been reported frequently in additive manufacturing (AM) as well as welding. In the vast majority of weldability tests, a single-pass, single-layer weld is tested, though multiple-pass, multiple-layer welding is common in welding practice. In AM, evaluating the [...] Read more.
Solidification cracking and liquation cracking have been reported frequently in additive manufacturing (AM) as well as welding. In the vast majority of weldability tests, a single-pass, single-layer weld is tested, though multiple-pass, multiple-layer welding is common in welding practice. In AM, evaluating the cracking susceptibility based on the total number or length of cracks per unit volume requires repeated cutting and polishing of a built object, and the cracks are often too small to open easily for fracture-surface examination. The present study identified an existing weldability test and modified it to serve as a cracking susceptibility test for AM. A single-pass, single-layer deposit of metal powder was made along a slender specimen that was pulled like in tensile testing but with acceleration. Cracks were visible on the deposit surface and opened easily for examination. The critical pulling speed, i.e., the minimum pulling speed required to cause cracking, was determined as an index for the cracking susceptibility. The lower the critical pulling speed is, the higher the cracking susceptibility. As a result, 6061 Al showed solidification cracking, and 7075 Al showed liquation cracking, consistent with their high susceptibility to such cracking. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: “Laser Welding and Additive Manufacturing”)
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19 pages, 6400 KB  
Article
Microstructure and Mechanical Property Regulation of As-Cast AlCoCrFeNi2.1Six (x = 0, 0.1, 0.2, 0.3) High-Entropy Alloys
by Rongbin Li, Saiya Li, Jiahao Zhang and Jiaming Tian
Metals 2025, 15(10), 1146; https://doi.org/10.3390/met15101146 - 16 Oct 2025
Viewed by 243
Abstract
Eutectic high-entropy alloys (EHEAs) combine the casting advantages of eutectic alloys with the comprehensive properties of high-entropy alloys, making them a research hotspot in the field of metallic materials. Among them, the AlCoCrFeNi2.1 EHEA has attracted significant attention due to its excellent [...] Read more.
Eutectic high-entropy alloys (EHEAs) combine the casting advantages of eutectic alloys with the comprehensive properties of high-entropy alloys, making them a research hotspot in the field of metallic materials. Among them, the AlCoCrFeNi2.1 EHEA has attracted significant attention due to its excellent strength–toughness balance characteristics. In this study, alloy samples of AlCoCrFeNi2.1Six (x = 0, 0.1, 0.2, 0.3) were prepared to investigate the regulatory effects of trace Si on its phase composition, microstructure, and mechanical properties. The results show that the base alloy AlCoCrFeNi2.1 is composed of an FCC and BCC phase composition. With the increase in the Si content to x = 0.3, the CrSi2 phase gradually precipitates in the alloy, and its microscopic morphology transforms from the regular lamellar to the dendrite and network structure. The introduction of Si significantly enhances the room-temperature microhardness, wear resistance, and yield strength of the alloy through the mechanisms of solid solution strengthening and second phase strengthening. However, an excessive addition leads to a decrease in ductility and toughness. This study reveals the role of Si in phase control and the strengthening and toughening mechanism of eutectic high-entropy alloys, providing experimental evidence and a theoretical reference for the design of high-performance silicon-modified high-entropy alloys. Full article
(This article belongs to the Section Entropic Alloys and Meta-Metals)
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18 pages, 4208 KB  
Article
Investigation of Single-Pass Laser Remelted Joint of Mo-5Re Alloy: Microstructure, Residual Stress and Angular Distortion
by Yifeng Wang, Danmin Peng, Xi Qiu, Mingwei Su, Shuwei Hu, Wenjie Li and Dean Deng
Metals 2025, 15(10), 1145; https://doi.org/10.3390/met15101145 - 15 Oct 2025
Viewed by 179
Abstract
Molybdenum-rhenium (Mo-Re) alloys, especially those with low Re content, have great potential in fabricating nuclear components. However, the extremely high melting point and high brittleness of Mo-Re alloys make them difficult to weld. In this study, laser welding was used to prepare single-pass [...] Read more.
Molybdenum-rhenium (Mo-Re) alloys, especially those with low Re content, have great potential in fabricating nuclear components. However, the extremely high melting point and high brittleness of Mo-Re alloys make them difficult to weld. In this study, laser welding was used to prepare single-pass remelted joint of Mo-5Re alloy with welding parameters of laser power 2800 W, welding speed 2 m·min−1 and argon gas flow rate 20 L·min−1. The microstructure of the remelted joint was investigated by the optical microscopy and the scanning electron microscopy. The microhardness distribution of the joint was analyzed. In addition, the temperature field, residual stress, and angular distortion of the joint were investigated by both numerical and experimental methods. The results show that columnar grains grew from the fusion boundary toward the center of the weld pool, and equiaxed grains formed in the central region of the fusion zone (FZ). In the heat-affected zone (HAZ), the grains transformed from initial elongated into equiaxed grains. The electron backscatter diffraction (EBSD) results revealed that high-angle grain boundaries (HAGBs) dominated in FZ. Oxide/carbide particles at grain boundaries and inside the grains can be inferred from contrast results. The average microhardness of FZ was 170 ± 5 (standard deviation) HV, which was approximately 80 HV lower than that of the base metal (250 ± 2 HV). Softening phenomenon was also observed in HAZ. The calculated weld pool shape showed high consistency with the experimental observation. The peak temperature (296 °C) of the simulated thermal cycling curve was ~8% higher than the measured value (275 °C). The residual stress calculation results indicated that FZ and its vicinity exhibited high levels of longitudinal tensile residual stresses. The simulated peak longitudinal residual stress (509 MPa) was ~30% higher than the measured value (393 MPa). Furthermore, both the simulation and experimental results demonstrated that the single-pass remelted joint of Mo-5Re alloy produced only minor angular distortion. The obtained results are very useful in understanding the basic phenomena and problems in laser welding of Mo alloys with low Re content. Full article
(This article belongs to the Special Issue Properties and Residual Stresses of Welded Alloys)
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17 pages, 2126 KB  
Article
Thin Film Fragmentation Testing: A Refined Screening Method for Estimating Relative Intrinsic Ductility of Refractory Metals
by Taohid Bin Nur Tuhser and Thomas John Balk
Metals 2025, 15(10), 1144; https://doi.org/10.3390/met15101144 - 15 Oct 2025
Viewed by 266
Abstract
Refractory metals typically exhibit limited room temperature ductility, hampering their widespread application. Recent advances in refractory high-entropy alloys have focused on finding optimum combinations of strength and ductility but require exploring vast compositional spaces. To facilitate such a search process, a method for [...] Read more.
Refractory metals typically exhibit limited room temperature ductility, hampering their widespread application. Recent advances in refractory high-entropy alloys have focused on finding optimum combinations of strength and ductility but require exploring vast compositional spaces. To facilitate such a search process, a method for fast assessment of intrinsic ductility would be highly advantageous. Herein, we propose a novel approach to screen for a refractory alloy’s ‘intrinsic ductility’ by leveraging the established technique of thin film fragmentation testing, which has been successfully used to evaluate stretchability of flexible electronics. We conducted in-depth investigations of sputtered tungsten thin films to identify the processing-induced extrinsic variables that can affect the crack onset strain (COS) under uniaxial loading. By tuning the process parameters for film deposition, Nb, Mo, Ta and W samples were fabricated with comparable thicknesses and residual stress levels. The films’ COS values were compared to the ductility levels of bulk counterpart materials, and the conditions for meaningful comparison are discussed. This approach offers a simple, inexpensive, and rapid means of screening based on relative intrinsic ductility of thin metal films and should also be applicable to the study of high-entropy alloy films. Full article
(This article belongs to the Special Issue Fracture and Fatigue of Advanced Metallic Materials)
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20 pages, 6475 KB  
Article
Study on Constructing Indoor Accelerated Simulation Methods for Steel with Galvalume Coating Exposed to Marine Atmosphere
by Luntao Wang, Hongkai Wang, Bo Li, Hao Yu, Hao Zhang, Junhang Chen, Chenghui Yin and Kui Xiao
Metals 2025, 15(10), 1143; https://doi.org/10.3390/met15101143 - 14 Oct 2025
Viewed by 166
Abstract
To investigate the corrosion behavior and mechanism of steel with galvalume coating (Zn–55%Al–1.6%Si) in marine atmospheric environments, an indoor accelerated corrosion test method was constructed. Both marine atmospheric exposure tests and spectrum-based accelerated corrosion tests were carried out to compare the corrosion kinetics, [...] Read more.
To investigate the corrosion behavior and mechanism of steel with galvalume coating (Zn–55%Al–1.6%Si) in marine atmospheric environments, an indoor accelerated corrosion test method was constructed. Both marine atmospheric exposure tests and spectrum-based accelerated corrosion tests were carried out to compare the corrosion kinetics, corrosion products, and electrochemical behavior. A corrosion prediction model was established using the weight-loss method. Surface morphologies were observed by scanning electron microscopy (SEM), the compositions of corrosion products were identified by X-ray diffraction (XRD), and electrochemical tests were conducted to elucidate the time-dependent electrochemical characteristics. The results showed that after two years of natural exposure and 16 cycles of accelerated testing, the specimens exhibited mainly uniform corrosion of the galvalume coating without significant localized corrosion. The corrosion products were primarily composed of ZnO, Zn5(OH)6(CO3)2, Zn5(OH)8Cl2·H2O, and Al2O3. The corrosion potential increased while the corrosion current density decreased with prolonged testing, indicating that the corrosion product film effectively inhibited corrosion and enhanced protection. By integrating the corrosion kinetics, product composition, and electrochemical mechanism from both outdoor and indoor tests, the constructed spectrum-based accelerated test method demonstrated good correlation with actual marine atmospheric corrosion processes, providing a reliable approach for evaluating the corrosion resistance and service life of steel with galvalume coating in marine environments. Full article
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11 pages, 2403 KB  
Article
Separation of REs from Ca and Mg Ions by Ammonium Bicarbonate Precipitation and the Influence of Fe and Al Ions
by Yanzhu Liu, Zhenghui Zhu, Fen Nie, Lihui Liu, Jinfei Shi and Yongxiu Li
Metals 2025, 15(10), 1142; https://doi.org/10.3390/met15101142 - 14 Oct 2025
Viewed by 262
Abstract
The presence of impurities such as Ca, Mg, and Al during the precipitation of rare earths (REs) using ammonium bicarbonate directly affects product purity. It is necessary to optimize precipitation methods and conditions to improve the separation efficiency between REs and impurities. In [...] Read more.
The presence of impurities such as Ca, Mg, and Al during the precipitation of rare earths (REs) using ammonium bicarbonate directly affects product purity. It is necessary to optimize precipitation methods and conditions to improve the separation efficiency between REs and impurities. In this study, RE (La and Ce) ions were precipitated using ammonium bicarbonate solution, and the separation efficiency of REs from Al, Fe, Ca, and Mg ions was investigated with or without the addition of triammonium citrate (TAC). The results showed that as long as the precipitation yield of REs was controlled below 94%, Ca and Mg ions would not enter the precipitation in the absence of other impurities, and the purity of the obtained rare earth oxides (RE2O3) was close to 100%. The presence of Al and Fe impurities would reduce the separation efficiency of REs from Ca and Mg. Therefore, Al and Fe must be separated before the precipitation of REs. First, Fe was completely precipitated by controlling the pH value to 4.12. Then, by filtering out the isolation and adjusting the pH value to 4.6, approximately 84% of Al3+ was precipitated, with a loss of REs of about 6%. Finally, the pH value was increased to 6.43, and REs were completely precipitated, yielding rare earth carbonate. The RE2O3 purity of its calcination product was 97.8% with Al and Mg contents of 1.05% and 0.21%, respectively, and no Ca or Fe was detected. This indicated that Mg can enter the product by co-precipitation with Al. To address this, a small amount of TAC was added during the pre-removal of Fe and Al to facilitate the complete removal of Al. By controlling the precipitation yield of REs at 94%, the purity of the final RE2O3 reached 99.6% with an Al content of 0.09%. Furthermore, using a continuous precipitation crystallization method, RE2O3 purity can be achieved at 99.8% with an Al content of 0.06%. Full article
(This article belongs to the Special Issue Hydrometallurgical Processes for the Recovery of Critical Metals)
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14 pages, 45103 KB  
Article
Tensile Performance Sensitivity to Variations of Standard 17-4 PH Heat Treatments on LPBF-Produced Material
by Ben Brown, Cory Read, Joseph Newkirk and Frank Liou
Metals 2025, 15(10), 1141; https://doi.org/10.3390/met15101141 - 14 Oct 2025
Viewed by 271
Abstract
Standard heat treatments for metals of a particular composition are typically designed with the assumption of a conventional starting microstructure, such as that produced by casting or wrought processing. When applied to metals fabricated by Laser Powder Bed Fusion (LPBF) metal additive manufacturing [...] Read more.
Standard heat treatments for metals of a particular composition are typically designed with the assumption of a conventional starting microstructure, such as that produced by casting or wrought processing. When applied to metals fabricated by Laser Powder Bed Fusion (LPBF) metal additive manufacturing (AM), these heat treatments can produce inconsistent performance due to the unique as-built microstructures. This study investigates how modifications to standard heat treatments for 17-4 PH steel influence the microstructure and mechanical properties of LPBF-fabricated material. Specimens were produced and subjected to varying solutionizing and homogenizing treatments followed by standard aging treatments. Microstructures were characterized using optical microscopy, Electron Backscatter Diffraction (EBSD), and X-ray diffraction (XRD), and mechanical properties were evaluated through uniaxial tensile testing. Based on these results, recommendations are provided for achieving improved wrought-like performance in LPBF 17-4 PH steel. Full article
(This article belongs to the Special Issue Advances in Laser Processing of Metals and Alloys)
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17 pages, 4803 KB  
Article
Effect of Refining Temperature and Refining Time on Purification and Composition Control of FGH95 Powder Metallurgy Superalloy Return Material During Vacuum Induction Melting
by Jiulong Chen, Xuqing Wang, Lei Zhou, Peng Fu, Ying Cheng and Huarui Zhang
Metals 2025, 15(10), 1140; https://doi.org/10.3390/met15101140 - 14 Oct 2025
Viewed by 277
Abstract
To promote the high-value recycling of machining return materials from powder metallurgy (P/M) FGH95 superalloy production, a vacuum induction melting refining process was developed to achieve gas impurity purification and compositional control. Cylindrical solid returns obtained from wire-cut electrical discharge machining were used [...] Read more.
To promote the high-value recycling of machining return materials from powder metallurgy (P/M) FGH95 superalloy production, a vacuum induction melting refining process was developed to achieve gas impurity purification and compositional control. Cylindrical solid returns obtained from wire-cut electrical discharge machining were used as feedstock, and the effects of refining temperature (1550–1650 °C) and holding time (10–30 min) on impurity removal and element stability were systematically investigated. For each condition, three repeated melts were performed, and the average gas contents (mean ± SD) were evaluated by inert-gas fusion analysis. Results show that at 1650 °C, O decreased from 8 ppm to 6 ppm, N decreased from 6 ppm to 3 ppm, while H remained below the detection limit (<1 ppm). Prolonged refining caused slight compositional deviations, with Cr exhibiting measurable volatilization, whereas Al and Ti showed minor increases (<0.06 wt.%). A kinetic model describing O removal was established, yielding an apparent activation energy of 128 kJ·mol−1, confirming diffusion-controlled deoxidation behavior. The optimal refining condition—1650 °C for 10 min—achieved efficient removal of O and H while maintaining alloy compositional stability. This study provides both a practical refining route and a kinetic basis for the purification and reuse of machining returns in nickel-based P/M superalloys, contributing to cost reduction and sustainable manufacturing. Full article
(This article belongs to the Special Issue Advances in Lightweight Alloys, 2nd Edition)
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20 pages, 8789 KB  
Article
The Effect of Hydrogen Embrittlement on Fracture Toughness of Cryogenic Steels
by Junggoo Park, Gyubaek An, Jeongung Park, Daehee Seong and Wonjun Jo
Metals 2025, 15(10), 1139; https://doi.org/10.3390/met15101139 - 13 Oct 2025
Viewed by 406
Abstract
This study investigates the effect of hydrogen embrittlement on the fracture toughness of 9% Ni steel and STS 316L stainless steel under cryogenic conditions ranging from −80 °C to −253 °C. Hydrogen charging was performed using electrochemical methods, and hydrogen uptake was quantitatively [...] Read more.
This study investigates the effect of hydrogen embrittlement on the fracture toughness of 9% Ni steel and STS 316L stainless steel under cryogenic conditions ranging from −80 °C to −253 °C. Hydrogen charging was performed using electrochemical methods, and hydrogen uptake was quantitatively analyzed using thermal desorption spectroscopy (TDS). Fracture toughness was evaluated using crack tip opening displacement (CTOD) testing per ISO 12135, both without hydrogen (WO-H) and with hydrogen (W-H). The results showed a gradual decrease in CTOD values with decreasing temperature in both steels under hydrogen-free conditions, with ductile fracture maintained even at −253 °C. In contrast, hydrogen-charged specimens exhibited significant toughness degradation at intermediate subzero temperatures (−80 °C to −130 °C), particularly in 9% Ni steel due to its BCC crystal structure. However, at −160 °C and below, the effect of hydrogen embrittlement was suppressed mainly owing to the reduced hydrogen diffusivity. Scanning electron microscopy (SEM) analysis confirmed the transition from ductile to brittle fracture with decreasing temperature and hydrogen influences. At −253 °C, fully brittle fracture surfaces were observed in all specimens, confirming that at ultra-low temperatures, fracture behavior is dominated by temperature effects rather than hydrogen. These findings identify a practical temperature limit (approximately −160 °C) below which hydrogen embrittlement becomes negligible, providing critical insights for the design and application of structural materials in hydrogen cryogenic environments. Full article
(This article belongs to the Special Issue Fatigue, Fracture, and Multiaxial Integrity of Metallic Structure Materials: From Microstructure to Data-Driven Assessment)
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17 pages, 12944 KB  
Article
Experimental Study on Backwater-Assisted Picosecond Laser Trepanning of 304 Stainless Steel
by Liang Wang, Rui Xia, Jie Zhou, Yefei Rong, Changjian Wu, Long Xu, Xiaoxu Han and Kaibo Xia
Metals 2025, 15(10), 1138; https://doi.org/10.3390/met15101138 - 13 Oct 2025
Viewed by 251
Abstract
This study focuses on the high-precision microhole machining of 304 stainless steel and explores a backwater-assisted picosecond laser trepanning technique. The laser used is a 30 W green picosecond laser with a wavelength of 532 nm, a repetition rate of 1000 kHz, and [...] Read more.
This study focuses on the high-precision microhole machining of 304 stainless steel and explores a backwater-assisted picosecond laser trepanning technique. The laser used is a 30 W green picosecond laser with a wavelength of 532 nm, a repetition rate of 1000 kHz, and a pulse width of less than 15 ps. Experiments were conducted under both water-based and non-water-based laser processing environments to systematically investigate the effects of laser power and scanning cycles on hole roundness, taper, and overall hole quality. The experimental results further confirm the advantages of the backwater-assisted technique in reducing slag accumulation, minimizing roundness variation, and improving hole uniformity. In addition, thermal effects during the machining process were analyzed, showing that the water-based environment effectively suppresses the expansion of the heat-affected zone and mitigates recast layer formation, thereby enhancing hole wall quality. Compared with conventional non-water-based methods, the backwater-assisted approach demonstrates superior processing stability, better hole morphology, and more efficient thermal management. This work provides a reliable technical route and theoretical foundation for precision microhole machining of stainless steel and exhibits strong potential for engineering applications. Full article
(This article belongs to the Special Issue Laser Processing of Metallic Material)
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23 pages, 1869 KB  
Article
Multi-Dimensional Uniform Cooling Process for Ship Plate Steel Continuous Casting
by Xiaodong Yang, Zhenyao Chen, Jianchao Guan, Xin Xie, Chun He, Hao Hu, Mujun Long, Jianhua Liu and Dengfu Chen
Metals 2025, 15(10), 1137; https://doi.org/10.3390/met15101137 - 13 Oct 2025
Viewed by 261
Abstract
In slab continuous casting, achieving uniform cooling in the secondary cooling zone is essential for ensuring both surface integrity and internal quality. To optimize the process for ship plate steel, a solidification heat transfer model was developed, incorporating radiation, water film evaporation, spray [...] Read more.
In slab continuous casting, achieving uniform cooling in the secondary cooling zone is essential for ensuring both surface integrity and internal quality. To optimize the process for ship plate steel, a solidification heat transfer model was developed, incorporating radiation, water film evaporation, spray impingement, and roll contact. The influence of secondary cooling water flow on slab temperature distribution was systematically investigated from multiple perspectives. The results show that a weak cooling strategy is crucial for maintaining higher surface temperatures and aligning the solidification endpoint with the soft reduction zone. Along the casting direction, a “strong-to-weak” cooling pattern effectively prevents abrupt temperature fluctuations, while reducing the inner-to-outer arc water ratio from 1.0 to 0.74 mitigates transverse thermal gradients. In addition, shutting off selected nozzles in the later stage of secondary cooling at medium and low casting speeds increases the slab corner temperature in the straightening zone by approximately 50 °C, thereby avoiding brittle temperature ranges. Overall, the proposed multi-dimensional uniform cooling strategy reduces temperature fluctuations and significantly improves slab quality, demonstrating strong potential for industrial application. Full article
(This article belongs to the Special Issue Advances in Continuous Casting and Refining of Steel)
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21 pages, 5267 KB  
Article
Effect of Increased Extrusion Ram Speed and Liquid Nitrogen Cooling on the Mechanical Properties of 6060 Aluminum Alloy
by Evangelos Giarmas, Emmanouil Tzimtzimis, Konstantinos Tsongas, Apostolos Korlos, Constantine David and Dimitrios Tzetzis
Metals 2025, 15(10), 1136; https://doi.org/10.3390/met15101136 - 12 Oct 2025
Viewed by 285
Abstract
This study investigates the impact of increased extrusion ram speed—achieved by utilizing liquid nitrogen as a die cooling agent—on the mechanical properties of a 6060-aluminum alloy. Mechanical characterization of the extruded profiles was performed using both tensile and nanoindentation tests. In addition, nanoindentation [...] Read more.
This study investigates the impact of increased extrusion ram speed—achieved by utilizing liquid nitrogen as a die cooling agent—on the mechanical properties of a 6060-aluminum alloy. Mechanical characterization of the extruded profiles was performed using both tensile and nanoindentation tests. In addition, nanoindentation was employed to evaluate creep behaviour and to extract key parameters, such as the steady-state creep strain rate. The findings indicate that while the enhanced ram speed has a minimal influence on Ultimate Tensile Strength (UTS) and Yield Tensile Strength (YTS), it has a more noticeable effect on elongation. Finite Element Analysis (FEA) was used in conjunction with nanoindentation data to model the mechanical behaviour of the alloy, showing good agreement with experimental tensile test results. This confirms the effectiveness of FEA-assisted nanoindentation as a reliable tool for mechanical assessment. Moreover, the results demonstrate that creep displacement is significantly influenced by the increased ram speed. However, the steady-state creep strain rate remained largely unaffected by variations in ram speed with the use of liquid nitrogen as a coolant. Notably, the creep stress exponent (n) was found to increase with higher ram speeds enabled by liquid nitrogen cooling. Full article
(This article belongs to the Special Issue Research and Application of Lightweight Metals)
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16 pages, 2494 KB  
Article
Martensitic Transformation Induced by B2 Phase Precipitation in an Fe-20 Ni-4.5 Al-1.0 C Alloy Steel Following Solution Treatment and Subsequent Isothermal Holding
by Rosemary Chemeli Korir, Yen-Ting Huang and Wei-Chun Cheng
Metals 2025, 15(10), 1135; https://doi.org/10.3390/met15101135 - 12 Oct 2025
Viewed by 278
Abstract
Phase transformations significantly influence the mechanical properties of Fe-based alloys, making their understanding essential for the design of high-performance alloy materials. This study investigates microstructural evolution and martensitic transformations induced by B2 phase precipitation in an Fe-20Ni-4.5Al-1.0C (wt.%) alloy. The alloy was solution-treated [...] Read more.
Phase transformations significantly influence the mechanical properties of Fe-based alloys, making their understanding essential for the design of high-performance alloy materials. This study investigates microstructural evolution and martensitic transformations induced by B2 phase precipitation in an Fe-20Ni-4.5Al-1.0C (wt.%) alloy. The alloy was solution-treated at 1100 °C, followed by isothermal holding between 750 °C and 1000 °C, and water quenching. Microstructural analysis revealed that the as-quenched alloy consisted of a single-phase austenite (γ). Isothermal holding led to the precipitation of a (Ni,Al)-rich B2 phase within the grains and along grain boundaries. An α′-martensitic phase was also observed within γ-grains adjacent to the B2 precipitates in the isothermally held samples. Martensitic transformation is attributed to localized nickel depletion in the matrix surrounding B2, which reduced γ-phase stability and raised the martensite start temperature (Ms), promoting γ-to-α′ transformation during cooling. The co-existence of B2 and α′ phases significantly increased the hardness of the alloy, with a maximum observed at an 850 °C holding temperature. At higher temperatures, coarsening and partial dissolution of B2, as well reduced martensite formation, led to a decline in hardness. These findings highlight the role of B2 precipitation in promoting martensitic transformation and optimizing mechanical properties through controlled heat treatment. Full article
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17 pages, 40494 KB  
Article
The Effect of Y Content on the Strength and Toughness of Mg-Y-Zn Alloys
by Dong Zhao, Jie Hu, Ruanyu Wang, Guoqing Yan, Wenkai Song, Liang Liang and Jian Peng
Metals 2025, 15(10), 1134; https://doi.org/10.3390/met15101134 - 12 Oct 2025
Viewed by 253
Abstract
The microstructure and properties of Mg-Y-Zn as-cast alloys with the Y/Zn ratio of approximately 1.3 (wt%) and different Y contents were studied, including an analysis of the main factors and mechanisms affecting their toughness and ductility, such as dendritic morphology, mass fraction of [...] Read more.
The microstructure and properties of Mg-Y-Zn as-cast alloys with the Y/Zn ratio of approximately 1.3 (wt%) and different Y contents were studied, including an analysis of the main factors and mechanisms affecting their toughness and ductility, such as dendritic morphology, mass fraction of different compound phases, and degree of solid solution. The results showed that the alloys with Y contents ranging from 3.5% to 5% exhibit high toughness. The 4.4% alloy has the best comprehensive mechanical properties with the UTS, YS, EL, and tensile deformation work of 188.9 MPa, 124.4 MPa, 5.9%, and 0.50 MJ/m2, respectively. It is beneficial for achieving higher strength and toughness by maintaining the content of the W phase and the combined content of the W phase and LPSO phase at approximately 5.8 wt% and 28.8 wt%, respectively. Full article
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