Metals

18 pages, 9023 KB

Open AccessArticle

Effect of Austempering Time and Temperature on the Mechanical and Microstructural Properties of a Niobium-Alloyed Austempered Ductile Iron

by César Yeshua Becerra Mayorga, Marissa Vargas Ramírez, Edgar Cardoso Legorreta, Jesús García Serrano, José Merced Martínez Vázquez, Erick Uriel Morales Cruz and Cynthia Aristeo Domínguez

Metals 2025, 15(11), 1168; https://doi.org/10.3390/met15111168 - 23 Oct 2025

Abstract

This study evaluated the influence of niobium addition and austempering time and temperature on the microstructure and mechanical behavior of ductile iron. Three alloys were produced: unalloyed ductile iron (H1) and two Nb-alloyed ductile iron (H2, 0.11 wt.% Nb and H3, 0.32 wt.% [...] Read more.

This study evaluated the influence of niobium addition and austempering time and temperature on the microstructure and mechanical behavior of ductile iron. Three alloys were produced: unalloyed ductile iron (H1) and two Nb-alloyed ductile iron (H2, 0.11 wt.% Nb and H3, 0.32 wt.% Nb). After austenitizing at 900 °C for 60 min, samples were austempered at 250 °C and 300 °C for 15, 30, 60, and 90 min. The as-cast microstructure of H3 exhibited a higher pearlite fraction (73.31 vol%) and increased carbide content (2.48 vol%), accompanied by reduced nodularity and nodule count. X-ray diffraction analysis revealed that the highest fraction of carbon-rich retained austenite was obtained in H3 after 30 min at 300 °C, reaching 42.48%. Hardness decreased with increasing retained austenite, confirming the inverse relationship between this phase and matrix strengthening. Wear testing showed that H2 presented slightly lower volume loss due to carbide precipitation, with the lowest value recorded after 15 min at 300 °C (1.088 mm³). Tensile tests indicated that ultimate tensile strength and yield strength were superior at 250 °C, with H3 achieving the highest values at 90 min (1353 and 1090 MPa, respectively). Overall, niobium promoted carbide formation and austenite stabilization, modifying the balance between hardness, toughness, and wear resistance in austempered ductile iron. Full article

(This article belongs to the Section Metal Casting, Forming and Heat Treatment)

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21 pages, 6101 KB

Open AccessArticle

The Mechanism of Microstructure Refinement and the Synergistic Strength–Ductility Enhancement in Al–Zn–Mg–Cu Alloys Processed by Continuous Rheo-Extrusion

by Ziren Wang, Jiazhi An, Mei Xu, Haixia Zhang, Guoli Wei, Chengliang Yang, Zhenpeng Wei, Wenzheng Shen and Wanwu Ding

Metals 2025, 15(11), 1167; https://doi.org/10.3390/met15111167 - 23 Oct 2025

Abstract

Al–Zn–Mg–Cu alloys are well known for their outstanding strength, toughness, and corrosion resistance, arising from the balanced addition of Mg, Zn, and Cu. However, conventional casting methods often lead to grain boundary segregation and the formation of coarse Fe-rich phases, which severely limit [...] Read more.

Al–Zn–Mg–Cu alloys are well known for their outstanding strength, toughness, and corrosion resistance, arising from the balanced addition of Mg, Zn, and Cu. However, conventional casting methods often lead to grain boundary segregation and the formation of coarse Fe-rich phases, which severely limit subsequent heat treatment and plastic processing. To overcome these drawbacks, this study systematically investigates the effects of the Continuous Rheo-Extrusion (CRE) process on the microstructure and mechanical performance of Al–Zn–Mg–Cu alloys using XRD, EBSD, SEM, and TEM analyses. The CRE process refines the average grain size from 53.5 μm to 16.1 μm and raises the fraction of high-angle grain boundaries to 88.8%. Moreover, coarse Fe-rich phases are fragmented to below 5 μm, while the elemental distribution of Zn, Mg, and Cu becomes more homogeneous, effectively reducing grain boundary segregation. The Al₂Cu precipitates are refined from 106.3 nm to 11.7 nm, corresponding to an 88.9% size reduction. These microstructural optimizations yield a remarkable increase in tensile strength (from 204.7 ± 23.7 MPa to 338.0 ± 9.3 MPa) and elongation (from 11.4 ± 2.4% to 13.8 ± 1.3%). Quantitative analysis confirms that dislocation and precipitation strengthening are the dominant contributors to this improvement. Overall, the CRE process enhances microstructural uniformity through the synergistic effects of shear deformation, continuous dynamic recrystallization (CDRX), and dynamic precipitation, thereby providing a solid theoretical and practical foundation for short-process fabrication of high-strength, high-ductility Al–Zn–Mg–Cu alloys. Full article

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47 pages, 19449 KB

Open AccessReview

Laser Cladding Remanufacturing of Metallic Components in High-End Agricultural Machinery and Equipment: Material Design, Processing, and Properties

by Haifei Lu, Hailong Yan, Jiming Lv, Weiwei Deng, Yuchen Liang, Xiang Xu, Jie Cai, Kaiyu Luo and Jinzhong Lu

Metals 2025, 15(11), 1166; https://doi.org/10.3390/met15111166 - 22 Oct 2025

Abstract

Harsh working environments and excessive usage frequency cause wear, fatigue, and corrosion failure in metallic components in high-end agricultural machinery and equipment. Overall replacements of valuable metallic components could result in high overhaul costs and material waste. Therefore, remanufacturing these local areas is [...] Read more.

Harsh working environments and excessive usage frequency cause wear, fatigue, and corrosion failure in metallic components in high-end agricultural machinery and equipment. Overall replacements of valuable metallic components could result in high overhaul costs and material waste. Therefore, remanufacturing these local areas is an effective way to put damaged components back into service, thus maximizing the value of the remaining materials. Laser cladding (LC) technology utilizes high-energy, high-density laser beams to create cladding layers with specialized properties such as wear and corrosion resistance on the surfaces of damaged metallic components. This work provides a comprehensive analysis of pre-processing, processing, and post-processing in relation to laser cladding remanufacturing (LCR) of metallic components. The review examines the LC process, including material systems (Fe-, Ni-, and Co-based alloys and composites), process optimization, and path planning. The relationship between material composition, process parameters, microstructure evolution, and resultant properties (wear, corrosion, and fatigue) is emphasized. Finally, challenges and future trends faced in this process are introduced in detail. The discussed topics provide some important insights on high-quality and efficient remanufacturing of metallic components in high-end agricultural machinery and equipment. Full article

(This article belongs to the Special Issue Laser Assisted Additive Manufacturing of Metals)

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18 pages, 8588 KB

Open AccessArticle

Effect of Cross- or Unidirectional Rolling on the Microstructure, Corrosion Rate, and Hemolysis of Ternary Magnesium–Zinc–Gallium Alloys

by Anabel Azucena Hernández-Cortés, José C. Escobedo-Bocardo, José Manuel Almanza-Robles and Dora Alicia Cortés-Hernández

Metals 2025, 15(11), 1165; https://doi.org/10.3390/met15111165 - 22 Oct 2025

Abstract

The effect of cross- or unidirectional rolling on the microstructure, corrosion rate, texture, and hemolysis of the Mg-0.5Zn-0.25Ga and Mg-1.5Zn-0.375Ga alloys was evaluated. After both rolling processes, the microstructure of the as-cast alloys was considerably refined due to the recrystallization process, obtaining higher [...] Read more.

The effect of cross- or unidirectional rolling on the microstructure, corrosion rate, texture, and hemolysis of the Mg-0.5Zn-0.25Ga and Mg-1.5Zn-0.375Ga alloys was evaluated. After both rolling processes, the microstructure of the as-cast alloys was considerably refined due to the recrystallization process, obtaining higher grain refinement after cross-rolling. The Mg-1.5Zn-0.375Ga alloy showed a finer microstructure than the Mg-0.5Zn-0.25Mg alloy due to the effect of both the severe plastic deformation obtained after cross-rolling and the higher amount of alloying elements, which act as grain refiners. After unidirectional rolling, the texture intensity of the basal plane increases, while the cross-rolled alloys show lower texture intensity due to the activation of the pyramidal and/or prismatic slip systems. The cross-rolled alloys showed a higher corrosion rate than the unidirectionally rolled alloys due to the basal texture developed. The Mg-1.5Zn-0.375Ga alloy showed a higher corrosion rate than the Mg-0.5Zn-0.25Ga alloy since the voids formed during heat treating were not fully eliminated during rolling. The Mg-0.5Zn-0.25Ga alloy after unidirectional rolling was not hemolytic (4.7%) and showed the lowest corrosion rate (0.8 mm/y). Thus, this alloy may be an excellent candidate for use in the fabrication of biodegradable implants. Full article

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Graphical abstract

12 pages, 1720 KB

Open AccessArticle

Construction of NiSe₂/WO₃@SiMPs Heterojunction with Enhanced Photoelectrochemical Performance

by Li Zhang, Jie Li, Jialu Liu, Zhuo Zhong, Yangyang Chen, Peng Yang and Hui Wang

Metals 2025, 15(11), 1164; https://doi.org/10.3390/met15111164 - 22 Oct 2025

Abstract

Monocrystalline silicon, despite its widespread use as a photoelectrode material, is hindered by inherent drawbacks, such as high surface reflectivity, vulnerability to oxide passivation, and instability in aqueous electrolytes. To address these, a micropyramidal texture is fabricated on the silicon surface via wet [...] Read more.

Monocrystalline silicon, despite its widespread use as a photoelectrode material, is hindered by inherent drawbacks, such as high surface reflectivity, vulnerability to oxide passivation, and instability in aqueous electrolytes. To address these, a micropyramidal texture is fabricated on the silicon surface via wet chemical etching. A heterojunction photoanode was constructed by sequentially depositing NiSe₂ and WO₃ onto the textured silicon using chemical bath deposition, forming NiSe₂/WO₃@SiMPs. The photoanode demonstrates optimal photoelectrochemical performance at a NiSe₂ to WO₃ mass ratio of 9:1. Under simulated solar illumination (AM 1.5 G, 100 mW cm⁻²), it achieves a photocurrent of 5.62 mA cm⁻² at 1.23 V (vs. RHE), and a maximum photocurrent of 13.6 mA cm⁻² at 2.0 V (vs. RHE), markedly outperforming the individual components NiSe₂@SiMPs (8.23 mA cm⁻²) and WO₃@SiMPs (0.95 mA cm⁻²) at 2.0 V (vs. RHE). Electrochemical impedance spectroscopy (EIS) results show a markedly lower charge transfer resistance (Rct) for the NiSe₂/WO₃@SiMPs (8.16 Ω) compared to the single-phase counterparts NiSe₂@SiMPs (121.48 Ω) and WO₃@SiMPs (902.23 Ω), indicating more efficient charge separation. In addition, the photocurrent remains steady for about 10 h without significant degradation. This work presents a promising strategy for improving the photoelectrochemical water splitting efficiency of silicon-based photoelectrodes through rational heterostructure engineering. Full article

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31 pages, 8000 KB

Open AccessReview

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

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

Open AccessArticle

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

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

{C N}^{-}

to

{C N O}^{-}

, as described by

({C N}^{-} + H_{2} O_{2} \to {C N O}^{-} + H_{2} O

). pH emerged as the dominant factor, optimizing radical stability and

{C N}^{-}

protonation (pK_a ≈ 9.21) at pH 10. Infrared spectroscopy confirmed the presence of cyanide complexes (

[A u {(C N)}_{2}]^{-}

,

[F e {(C N)}_{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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20 pages, 4904 KB

Open AccessArticle

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

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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14 pages, 2414 KB

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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, 199 KB

Open AccessEditorial

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 - 20 Oct 2025

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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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