Metals

18 pages, 13799 KB

Open AccessArticle

First-Principles Predictions of the Structural, Elastic, Electronic, Magnetic, and Thermal Properties of Equiatomic FeMnLiSi and FeMnLiGe Quaternary Heusler Alloys

by Guoqi Zhao, Yufeng Wen, Yanlin Yu and Wen Pan

Metals 2026, 16(8), 883; https://doi.org/10.3390/met16080883 (registering DOI) - 9 Aug 2026

Abstract

In this work, first-principles calculations based on density functional theory were employed to investigate the structural, elastic, half-metallic, magnetic, and thermal properties of two novel quaternary Heusler alloys, FeMnLiSi and FeMnLiGe. The results revealed that ferrimagnetic FeMnLiSi and FeMnLiGe with type III structures [...] Read more.

In this work, first-principles calculations based on density functional theory were employed to investigate the structural, elastic, half-metallic, magnetic, and thermal properties of two novel quaternary Heusler alloys, FeMnLiSi and FeMnLiGe. The results revealed that ferrimagnetic FeMnLiSi and FeMnLiGe with type III structures were energetically the most stable, and possessed thermodynamic, dynamic, and mechanical stabilities. Their equilibrium lattice constants were 5.6104 Å and 5.7479 Å. At equilibrium, FeMnLiSi and FeMnLiGe exhibited brittleness, elastic anisotropy, and half-metallic ferrimagnetism, with half-metallic band gaps of 0.7935 eV and 1.0805 eV, respectively. The total magnetic moments per unit cell of FeMnLiSi and FeMnLiGe were both 2.0000 µB, which conforms to the Slater-Pauling rule. Their half-metallic ferrimagnetism remained robust over a broad range of uniform lattice strains. FeMnLiSi exhibited a higher stability, melting point, and Debye temperature, as well as a narrower half-metallic gap, than FeMnLiGe. This work systematically predicted the intrinsic structural, mechanical, magnetic, and thermal properties of FeMnLiSi and FeMnLiGe, and delivered theoretical insights for designing new Heusler-type half-metallic candidates. Full article

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18 pages, 13783 KB

Open AccessArticle

Optimized Electroless Deposition of Co on Activated WC Powders for WC-Co Cemented Carbides with Enhanced Mechanical Performance

by Shenggang Wang, Jiao Shi, Chang Yu and Haitao Xu

Metals 2026, 16(8), 882; https://doi.org/10.3390/met16080882 (registering DOI) - 8 Aug 2026

Abstract

High-quality WC-Co composite powder is the prerequisite for achieving cemented carbides with superior mechanical properties. However, achieving homogeneous Co distribution on WC particles remains challenging due to the limited surface activity of WC and the high cost associated with noble-metal activation methods. Therefore, [...] Read more.

High-quality WC-Co composite powder is the prerequisite for achieving cemented carbides with superior mechanical properties. However, achieving homogeneous Co distribution on WC particles remains challenging due to the limited surface activity of WC and the high cost associated with noble-metal activation methods. Therefore, this study employed an electroless plating method based on non-noble-metal activation to prepare Co- coated WC composite powders and to clarify the effects of plating parameters on coating behavior, microstructure evolution, and mechanical properties of WC-Co cemented carbides. Results indicate that when plated with a lower reducing-agent concentration (15 g/L) or a lower temperature (70 °C), insufficient Co coating causes poor fracture toughness of the cemented carbides. Increasing the reducing-agent concentration to 25 g/L or the plating temperature to 80 °C promotes a more uniform Co distribution on WC particles, which suppresses WC grain coalescence during sintering. Under the optimized reducing-agent concentration of 25 g/L, the obtained WC-Co cemented carbide exhibits a homogeneous microstructure with an average WC grain size of 0.91 μm, a Vickers hardness of 2054.5 HV30, and a fracture toughness of 11.39 MPa·m^1/2. Excessive reducing-agent concentration or plating temperature deteriorates the Co coating uniformity, promoting Co aggregation and grain coarsening of the cemented carbides. This work demonstrates that precise control of electroless plating parameters enables the fabrication of high-quality WC-Co composite powders, providing a practical route for tailoring microstructure and optimizing mechanical performance of the cemented carbides. Full article

(This article belongs to the Special Issue Advances in Design, Processing and Characterization of Cemented Carbide)

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12 pages, 4378 KB

Open AccessArticle

TD Salt-Bath Vanadizing Process and Coating Properties of 9SiCr Steel

by Hui Chen, Jun Sun, Li Shang and Chao Jia

Metals 2026, 16(8), 881; https://doi.org/10.3390/met16080881 (registering DOI) - 8 Aug 2026

Abstract

Tool steel TD salt-bath vanadizing generally relies on expensive analytical-grade raw materials, yet systematic investigations into low-cost industrial borax-based vanadizing of 9SiCr steel remain insufficient. This work intends to optimize the industrial salt-bath vanadizing process and clarify the growth mechanism of vanadium carbide [...] Read more.

Tool steel TD salt-bath vanadizing generally relies on expensive analytical-grade raw materials, yet systematic investigations into low-cost industrial borax-based vanadizing of 9SiCr steel remain insufficient. This work intends to optimize the industrial salt-bath vanadizing process and clarify the growth mechanism of vanadium carbide coatings. TD thermal diffusion vanadizing was performed on 9SiCr steel using a molten borax salt bath containing industrial-grade borax and V₂O₅. Metallurgical microscopy, XRD, SEM-EDS and microhardness testing were adopted to systematically explore the effects of treatment temperature and holding time on coating thickness, microstructure and hardness. Continuous, dense VC coatings with favorable metallurgical bonding were fabricated. Coating thickness increased linearly with temperature and followed a parabolic growth law with respect to holding time. The optimized parameter was identified as 970 °C for 4 h, yielding a 8.3 μm thick coating with an average microhardness of ~2500 HV and an 8 μm thick diffusion transition layer. Comparative chromizing experiments indicated that the chromium carbide coating (16.7 μm) was approximately twice the thickness of the VC coating under identical conditions, demonstrating that VC coating growth is restricted by the diffusion supply of active carbon from the substrate. This research provides experimental data and theoretical guidance for the industrialized optimization of TD salt-bath vanadizing for 9SiCr steel. Full article

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23 pages, 6972 KB

Open AccessArticle

Springback Prediction in Sheet-Metal Bending Based on Finite Element Method and Artificial Neural Network with Shapley Additive Explanations Method

by Peter Mulidrán, Emil Spišák, Miroslav Tomáš and Janka Majerníková

Metals 2026, 16(8), 880; https://doi.org/10.3390/met16080880 - 7 Aug 2026

Abstract

The main objective of this paper is to present a comparative analysis between the finite element method (FEM) and artificial neural networks (ANNs) for predicting sheet metal springback, while addressing the “black-box” nature of machine learning through explainable AI (XAI). To achieve this [...] Read more.

The main objective of this paper is to present a comparative analysis between the finite element method (FEM) and artificial neural networks (ANNs) for predicting sheet metal springback, while addressing the “black-box” nature of machine learning through explainable AI (XAI). To achieve this novelty, a multi-layer perceptron (MLP) architecture was implemented and evaluated against numerical simulations during the bending of a hat-shaped profile. The experimental framework utilized dual-phase HCT600X steel (0.8 mm thickness), supplemented by deep-drawing DC06 and high-strength RAK40/70 steels to ensure dataset diversity and robust generalization capability. A key contribution of this work is the integration of local SHAP (Shapley additive explanations) analysis to interpret the ANN outputs, allowing for a precise quantification and rank ordering of how individual material, design, and process parameters govern the resulting springback angle. The developed MLP model (comprising two hidden layers with five neurons each) achieved high predictive fidelity, yielding an overall correlation coefficient R = 0.99074 alongside robust error metrics (RMSE and MAE). Full article

(This article belongs to the Special Issue Characterization and Modeling of Microstructure Evolution During Metallic Material Processing)

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16 pages, 1089 KB

Open AccessArticle

Limits of Acid Dosage for Metal Dissolution During Leaching of Pyrolyzed NMC Black Mass in Different Acids

by Monika Keutmann, Kirill Saushkin and Bernd Friedrich

Metals 2026, 16(8), 879; https://doi.org/10.3390/met16080879 - 7 Aug 2026

Abstract

This study investigated how acid concentration affects leaching from pyrolyzed LIBs’ (lithium-ion batteries’) black mass (BM) by stepwise acidification with eight acids at 70 °C under identical starting conditions. A citric-acid control without BM matched the calculated pH, whereas BM buffered solutions to [...] Read more.

This study investigated how acid concentration affects leaching from pyrolyzed LIBs’ (lithium-ion batteries’) black mass (BM) by stepwise acidification with eight acids at 70 °C under identical starting conditions. A citric-acid control without BM matched the calculated pH, whereas BM buffered solutions to ∼pH 9.5 and increased the measured pH. Stabilized pH provided a consistent reference within each experiment, but similar pH values across acids produced very different leaching efficiencies. At pH ≈ 3, lithium leaching was ∼pH 85% for formic acid and ∼pH 60% for citric acid. The maximum lithium leaching ranged from 49% (ascorbic acid) to 92% (sulfuric acid), while organic acids often showed limited cobalt and nickel dissolution. For formic acid, speciation and metal-formate solubility calculations showed that higher acid concentration does not necessarily increase transition-metal leaching and may suppress cobalt and nickel. Thus, pH is stable within each acid system but not transferable across acids, and high solid loading (250 g L⁻¹) further requires acid-specific evaluation. The results indicate that acid-dependent speciation and complexation, rather than proton concentration alone, control extraction and can decouple acid dosage from leaching performance. Full article

(This article belongs to the Section Extractive Metallurgy)

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23 pages, 12671 KB

Open AccessReview

Review of Mineral Structures and Advances in Lithium Extraction from Lithium-Bearing Ores

by Chenhao Li, Long Meng, Zhengjie Chen, Zhihui Yu, Yu Wang, Jue Chen, Xiaolan Wang, Lijuan Sun, Qiqiang Wang, Wendi Zhang, Otgonjargal Enkhtur, Zhiwei Bian, Jingkui Qu and Shaoyuan Li

Metals 2026, 16(8), 878; https://doi.org/10.3390/met16080878 - 7 Aug 2026

Abstract

Lithium extraction from ores is the main source of lithium salts in China, and the development of green and efficient extraction technologies is an inevitable trend in the country’s lithium industry. Due to the limited availability of domestic lithium ore resources, the efficient [...] Read more.

Lithium extraction from ores is the main source of lithium salts in China, and the development of green and efficient extraction technologies is an inevitable trend in the country’s lithium industry. Due to the limited availability of domestic lithium ore resources, the efficient utilization of low-grade ores and the development of extraction processes from non-traditional lithium resources will be essential for reducing costs and improving efficiency. This review summarizes the resource characteristics and mineral structures of typical lithium-bearing ores, examines recent advances in extraction processes for representative lithium deposits (spodumene, lepidolite) and discusses strategies for the efficient utilization of low-grade lithium ores (zinnwaldite, petalite, amblygonite, clay-type lithium ore, and jadarite). Finally, the research gap in life cycle assessment of lithium extraction processes from multiple types of lithium ores is addressed by providing a useful reference framework for the development and optimization of lithium extraction technologies from ores. Full article

(This article belongs to the Special Issue Comprehensive Recycling of Metallurgical Solid Waste and Mineral Resources (2nd Volume))

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17 pages, 12880 KB

Open AccessArticle

Rotary Bending Fatigue of 6201 Aluminum Alloy Individual Wires

by Yaojun Miao, Chongmin She, Zhou Feng, Kezhen Li, Taian Chen, Jiafen Cao, Jianqiang Zhang, Haiyan Gao, Haiyang Jiang, Baode Sun, Jian Wang and Yufei Wang

Metals 2026, 16(8), 877; https://doi.org/10.3390/met16080877 - 7 Aug 2026

Abstract

Based on the rotary bending loading principle, an experimental investigation into the fatigue properties of 6201 aluminum alloy individual wires is presented. Considering the long design service life, high-cycle fatigue (HCF) behavior, and slender geometry (high length-to-diameter ratio) of these wires, a high-speed [...] Read more.

Based on the rotary bending loading principle, an experimental investigation into the fatigue properties of 6201 aluminum alloy individual wires is presented. Considering the long design service life, high-cycle fatigue (HCF) behavior, and slender geometry (high length-to-diameter ratio) of these wires, a high-speed rotary bending fatigue test platform is custom-designed and constructed. The design mechanically maximizes the probability of fracture at the midpoint of the constant-cross-section specimen, even when considering clamping damage at the ends. Through mechanical derivation for the test platform, based on the beam bending theory and the finite element method, a quantitative relationship is established between the bending stress amplitude and the deflection angle at the clamped end. Using this platform, the fatigue lives of 6201 aluminum alloy individual wires under various bending stress amplitudes are tested, and the stress–life (S-N) curve is obtained. The developed experimental method and the reported fatigue data in this study provide essential experimental and material data for fatigue life prediction and engineering design of 6201 aluminum alloy individual wires. Full article

(This article belongs to the Special Issue Fatigue Behavior of Metals and Alloys: State of the Art)

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15 pages, 5224 KB

Open AccessArticle

Casting of Al-1%Si Strip Using Single-Roll Caster Equipped with Scraper

by Toshio Haga and Hirofumi Sakaue

Metals 2026, 16(8), 876; https://doi.org/10.3390/met16080876 - 7 Aug 2026

Abstract

The high-speed, low-load twin-roll casting of Al-Si alloys with a Si content of approximately 1 at% is needed to prevent the occurrence of cracks. In twin-roll casting, however, the roll load reaches the lower limit required for the sufficient solidification of the aluminum [...] Read more.

The high-speed, low-load twin-roll casting of Al-Si alloys with a Si content of approximately 1 at% is needed to prevent the occurrence of cracks. In twin-roll casting, however, the roll load reaches the lower limit required for the sufficient solidification of the aluminum alloy. In this study, a single-roll caster equipped with a scraper was used to cast strips without cracks. The semi-solid forming of the free-solidified surface of an Al-1%Si strip during casting using a single-roll caster was attempted with a scraper under a very small load at a high roll speed of 30 m/min. The effects of the scraper angle and the scraper load on the condition of the scraped surface were investigated. The roll-contact surface and scraped surface of the strips cast under the appropriate conditions were compared by bending and deep drawing tests. After cold-rolling and annealing, no differences were observed between the roll-contact surface and the scraped surface. A sound Al-1%Si strip without cracks can be cast using a single-roll caster equipped with a scraper at a speed of 30 m/min. Full article

(This article belongs to the Special Issue Advanced Metal Casting Processes: Latest Research, Insights, and Challenges)

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26 pages, 46771 KB

Open AccessArticle

In Situ Network-like Bimodal Structure for Superior Strength-Ductility Synergy in WE43 Magnesium Alloy Fabricated via Powder Metallurgy

by Guotian Cao, Miao Chen, Huan Yu, Jixue Zhou, Jinzhe Jiang, Qian Su, Peng Zhang, Junpeng Duan, Kaiming Cheng, Dongqing Zhao, Xuansheng Feng and Yuansheng Yang

Metals 2026, 16(8), 875; https://doi.org/10.3390/met16080875 - 7 Aug 2026

Abstract

A rare-earth (RE)-segregation-assisted route combining mechanical alloying and hot extrusion was used to produce a WE43 alloy with an in situ network-like bimodal structure. Mechanical alloying fragmented and partially dissolved RE-containing phases produced a supersaturated Mg-RE solid solution, and dispersed oxygen-bearing surface films. [...] Read more.

A rare-earth (RE)-segregation-assisted route combining mechanical alloying and hot extrusion was used to produce a WE43 alloy with an in situ network-like bimodal structure. Mechanical alloying fragmented and partially dissolved RE-containing phases produced a supersaturated Mg-RE solid solution, and dispersed oxygen-bearing surface films. During the pre-sintering stage before hot extrusion, defect-rich prior powder-particle boundaries (PPBs) acted as preferential sinks for RE solutes, establishing RE-enriched regions before extrusion, while some oxygen-bearing species remained near PPBs and grain boundaries. During subsequent hot extrusion, RE solute drag and pinning by RE-containing precipitates and retained oxides restricted grain-boundary migration near PPBs, whereas rotation-assisted grain coalescence and growth occurred within particle interiors. In the 350—extruded alloy, the relatively coarse and fine grains averaged 299 and 144 nm and occupied 71 and 29 vol.%, while the precipitates averaged 97.1 and 9.2 nm. The 400—extruded alloy achieved a yield strength of 396 MPa, an ultimate tensile strength of 432 MPa, and an elongation of 7.9%. For the 350—extruded alloy, Orowan-type, solid-solution, grain-boundary, and dislocation strengthening contributed approximately 118.5, 116.8, 84, and 67 MPa, respectively, leaving an unresolved residual difference of 63.7 MPa. Coupled RE redistribution and oxide dispersion therefore provide a route to a favorable strength–ductility balance in powder-metallurgy Mg alloys. Full article

(This article belongs to the Special Issue Light Metals for Automotive Applications)

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22 pages, 2482 KB

Open AccessArticle

Theoretical Investigation on the Critical Thickness Conditions and Development of a Minimal Producible Thickness Model for Thin Strip Rolling

by Xiao Liu, Lipu Xu, Tao Wang, Zhongkai Ren, Hong Xiao and Jiang Ji

Metals 2026, 16(8), 874; https://doi.org/10.3390/met16080874 - 7 Aug 2026

Abstract

The growing demand for high-precision thickness control in cold rolling of metal strips calls for continuous improvement in rolling force prediction models. Classical thin-strip rolling theories, notably the Stone model, are based on the assumption of a circular roll arc profile within the [...] Read more.

The growing demand for high-precision thickness control in cold rolling of metal strips calls for continuous improvement in rolling force prediction models. Classical thin-strip rolling theories, notably the Stone model, are based on the assumption of a circular roll arc profile within the contact deformation zone. In practice, however, this assumption often becomes invalid owing to the emergence of a neutral zone under specific rolling conditions, which introduces considerable errors in force calculation and compromises model applicability. To address this issue, the present study develops a numerical analysis framework for thin-strip rolling processes across a range of initial thicknesses and reductions. The proposed method quantitatively captures the effects of single-pass reduction on roll shape evolution and contact pressure distribution along the deformation arc. In addition, a limiting producible thickness model is proposed by incorporating the deformation efficiency of the strip material. This approach enables the precise delineation of a neutral-zone-free deformation regime and establishes a criterion for determining the optimal single-pass reduction based on the ratio of initial thickness to Stone minimum rolling thickness. For given initial thickness and process parameters, a critical single-pass reduction exists that eliminates the neutral zone, yielding a characteristic curve that divides the rolling regimes: above it, the neutral zone vanishes, the Stone model applies, and efficiency is high; below it, a finite neutral zone persists, partially dissipating rolling force in elastic deformation, though rolling remains viable within limits. These findings provide a robust basis for improving rolling force accuracy and pass optimization, ultimately enhancing product quality and forming efficiency in precision strip manufacturing. Full article

(This article belongs to the Special Issue Advanced Rolling Technologies of Steels and Alloys)

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22 pages, 22887 KB

Open AccessReview

Review on Metal Micro-Hole Machining and Its Composite Machining Technologies: Current Status and Progress

by Yaowu Zhou, Yang Liu and Zhaozhi Wu

Metals 2026, 16(8), 873; https://doi.org/10.3390/met16080873 - 7 Aug 2026

Abstract

The advanced manufacturing of metal micro-holes is of great significance in various fields of industrial production, including aerospace, automotive, electronics, and healthcare. New technologies are constantly emerging, including various multi-energy field manufacturing technologies, and the knowledge system is complex and intricate. The present [...] Read more.

The advanced manufacturing of metal micro-holes is of great significance in various fields of industrial production, including aerospace, automotive, electronics, and healthcare. New technologies are constantly emerging, including various multi-energy field manufacturing technologies, and the knowledge system is complex and intricate. The present article summarizes recent advancements in metal micro-hole manufacturing technologies, drawing parallels with existing laser processing and electrochemical processing technologies. The present systematic review has been conducted with the objective of providing a comprehensive overview of the latest methodologies. The present review paper is of particular significance in that it encompasses not only the fundamental principles and innovative process methods, but also the most recent research progress and current problems. Furthermore, a synopsis of the developmental trajectory of advanced sustainable manufacturing technology for micro-holes was furnished. Full article

(This article belongs to the Special Issue High-Energy Beam Machining of Metals)

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31 pages, 52334 KB

Open AccessArticle

Modification of Surface and Subsurface Properties of Additively Manufactured Inconel 718 Components Through Post-Process and Interlayer Machine Hammer Peening

by Mohammad Dadgar, Martina Müller, Max Meerkamp, Tim Herrig, Stefan Gräfe and Thomas Bergs

Metals 2026, 16(8), 872; https://doi.org/10.3390/met16080872 - 7 Aug 2026

Abstract

Additive manufacturing (AM) enables rapid, near-net-shape fabrication with high material efficiency, but the resulting components often exhibit surface roughness, microstructural heterogeneity, and tensile residual stresses that reduce their performance. Machine hammer peening (MHP) is a mechanical surface treatment capable of modifying the surface [...] Read more.

Additive manufacturing (AM) enables rapid, near-net-shape fabrication with high material efficiency, but the resulting components often exhibit surface roughness, microstructural heterogeneity, and tensile residual stresses that reduce their performance. Machine hammer peening (MHP) is a mechanical surface treatment capable of modifying the surface integrity of AM components. It can be applied either as a conventional post-processing step after fabrication or as a hybrid interlayer treatment integrated into the build process. In this study, the effects of MHP process parameters and treatment strategies on wire-based laser metal deposition (LMD-w) Inconel 718 components were investigated, including the implementation of hybrid interlayer MHP. Surface topography, hardness, microstructure, and residual stresses were examined experimentally, while numerical simulations were developed to support the measurements and to characterize local contact conditions and plastic strain evolution during peening. The results show that MHP significantly reduces surface waviness and roughness, increases near-surface hardness, refines the microstructure, and introduces deep compressive residual stresses. Furthermore, hybrid interlayer MHP enhances the depth and uniformity of the modified layer by influencing the evolving microstructure during deposition. Standard forged Inconel 718 samples were also treated with MHP as a reference, showing comparable characteristics between the forged and AM components. These findings demonstrate that MHP is a versatile and effective modification technique for improving the performance and reliability of AM components, particularly when implemented as a hybrid interlayer treatment during the AM process. Full article

(This article belongs to the Special Issue Advances in Microstructure Evolution and Mechanical Properties of Additively Manufactured Metals and Alloys)

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41 pages, 31088 KB

Open AccessReview

Metal Powder Recycling in Additive Manufacturing: A Review of Pathways and Opportunities

by Michael Isakhani Zakaria and Janne Sundelin

Metals 2026, 16(8), 871; https://doi.org/10.3390/met16080871 - 6 Aug 2026

Abstract

Metal additive manufacturing (AM) plays an increasingly important role in sustainable production owing to its material efficiency, design freedom, and compatibility with circular economy (CE) strategies. Yet the high cost and environmental burden of producing virgin metallic powders remain major barriers to large-scale [...] Read more.

Metal additive manufacturing (AM) plays an increasingly important role in sustainable production owing to its material efficiency, design freedom, and compatibility with circular economy (CE) strategies. Yet the high cost and environmental burden of producing virgin metallic powders remain major barriers to large-scale adoption. This review synthesizes current and emerging approaches for recycling metallic powder feedstocks within AM, organizing them into four pathways: reusing, reconditioning, repurposing, and resourcing. Reusing preserves powders within the AM loop through controlled handling and qualification strategies, whereas reconditioning applies mechanical, thermal or chemical treatments to restore powder properties. Repurposing redirects powder to alternative value-added routes, including wire feedstock, metal–polymer composites, extrusion materials, and elemental or oxide recovery. Resourcing generates new powder from end-of-life powder, printing scrap, and waste through mechanical size reduction, atomization-based processes, or solid-state conversion routes. Across these pathways, the review highlights technological advances, process limitations, and cross-cutting challenges related to oxidation, morphology deterioration, contamination, and scalability, and identifies underexplored methodologies with potential for AM-specific recycling. By integrating insights across the field, this work outlines the expanding landscape of metallic powder circularity and demonstrates how diversified recycling strategies can reduce environmental impact, lower material costs, and support a more sustainable AM ecosystem. Full article

(This article belongs to the Section Additive Manufacturing)

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16 pages, 7002 KB

Open AccessArticle

Effects of Friction Stir Additive Deposition Process Under Different Cooling Conditions on the Microstructure and Mechanical Properties of 2195 Al-Li Alloy

by Qiang Zhou, Jiamin Yao, Yongsheng Gao, Botao Hu, Tong Feng and Chao Zhang

Metals 2026, 16(8), 870; https://doi.org/10.3390/met16080870 - 6 Aug 2026

Abstract

This study investigates the effects of air cooling and water mist cooling on the microstructure and mechanical properties of friction stir additive manufactured Al-Cu-Li alloy. The results show that under air cooling, coarse grains (average 15.37 μm) form, accompanied by coarse θ phase [...] Read more.

This study investigates the effects of air cooling and water mist cooling on the microstructure and mechanical properties of friction stir additive manufactured Al-Cu-Li alloy. The results show that under air cooling, coarse grains (average 15.37 μm) form, accompanied by coarse θ phase (Al₂Cu), S phase (Al₂CuMg), and Fe-containing brittle intermetallic compounds. A strong texture is observed (P_max = 6.45), and the tensile fracture surface exhibits a mixed ductile–brittle fracture mode with the coexistence of cleavage facets and dimples. The tensile strength, yield strength, and elongation are 325 MPa, 165 MPa, and 21%, respectively. Water mist cooling significantly refines the grain size (average 5.15 μm), weakens the texture (P_max = 5.41), suppresses the formation of detrimental Fe-containing phases, and promotes the precipitation of fine, dispersed θ phase and T1 phase (Al₂CuLi) (~200 nm). The fracture surface transforms into a uniformly dimpled ductile fracture. Mechanical properties are simultaneously improved: tensile strength reaches 348 MPa (+7%), yield strength 182 MPa (+10%), and elongation 24.5% (+17%). Rapid cooling achieves a synergistic optimization of strength and ductility through grain refinement strengthening, precipitation strengthening, and elimination of harmful phases. Full article

(This article belongs to the Section Additive Manufacturing)

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2 pages, 382 KB

Open AccessCorrection

Correction: Peng et al. A First-Principles Study of the Structural and Thermo-Mechanical Properties of Tungsten-Based Plasma-Facing Materials. Metals 2024, 14, 1197

by Jie Peng, Yichen Qian and David Cereceda

Metals 2026, 16(8), 869; https://doi.org/10.3390/met16080869 - 6 Aug 2026

Abstract

In the original publication [...] Full article

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20 pages, 4696 KB

Open AccessArticle

Prediction of Induction Hardening Depth of Wind Turbine Slewing Bearing with Magnetic Flux Concentrators

by Yeong-Jun An, Jun-Pyo Hong, Hyeon-Seung Jin, Min-Guk Kim, Sun-Ho Shin and Jong-Hun Kang

Metals 2026, 16(8), 868; https://doi.org/10.3390/met16080868 - 6 Aug 2026

Abstract

Large slewing bearings for wind turbines require sufficient hardening depth due to high contact stresses and cyclic loads. In this study, we combined electromagnetic–thermal–phase-transition coupled finite element analysis (FEA) with a surrogate model to predict the induction hardening depth of a dual-inductor system [...] Read more.

Large slewing bearings for wind turbines require sufficient hardening depth due to high contact stresses and cyclic loads. In this study, we combined electromagnetic–thermal–phase-transition coupled finite element analysis (FEA) with a surrogate model to predict the induction hardening depth of a dual-inductor system equipped with a magnetic flux concentrator. The air gap and the currents applied to the two inductors were used as input variables, and the hardening depth at five locations was calculated using FEA. Position 4 was identified as the critical location where the minimum hardening depth occurs. Since predictions based on limited FEA data may lead to overfitting and validation uncertainty, DNN, RSM, GPR, and SVR were compared, and LOOCV was applied to the comparison models. DNN predictions were adopted for the selection of candidate process conditions. When A1 and A2 were 8200 A and 8600 A, respectively, the predicted hardening depth was 6.17 mm. Under these conditions, additional FEA results showed a depth of 6.38 mm, while prototype measurements indicated 6.20 mm, representing a difference of 2.90%. This approach can be utilized to select candidate induction hardening conditions within the reviewed process range. Full article

(This article belongs to the Section Computation and Simulation on Metals)

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19 pages, 7861 KB

Open AccessArticle

Effect of Heat Treatment Duration on Microstructure and Properties of 2205 Duplex Stainless Steel Fabricated by Laser-Directed Energy Deposition

by Bin Zhao, Kuanjun Zhu, Bin Liu, Jinshan Wang, Junhui Li and Jian Gu

Metals 2026, 16(8), 867; https://doi.org/10.3390/met16080867 - 6 Aug 2026

Abstract

In this work, the microstructural evolution and comprehensive performances (mechanical, wear, and corrosion resistance) of LDED-fabricated 2205 DSS subjected to heat treatment at 1000 °C for different holding durations (5 min, 10 min, 30 min, and 60 min) were systematically investigated. The results [...] Read more.

In this work, the microstructural evolution and comprehensive performances (mechanical, wear, and corrosion resistance) of LDED-fabricated 2205 DSS subjected to heat treatment at 1000 °C for different holding durations (5 min, 10 min, 30 min, and 60 min) were systematically investigated. The results indicate that the austenite content gradually increases with the extension of heat treatment time, reaching a peak value of 51% at 30 min. Meanwhile, the austenite morphology transforms from dendritic grains to equiaxed grains, accompanied by the massive precipitation of intragranular austenite (IGA) and obvious elemental enrichment behavior. In terms of mechanical and functional performances, the microhardness decreases slightly with prolonged heat treatment, with a total reduction of only 7%. The elongation increases continuously, while the yield strength and tensile strength remain relatively stable. Additionally, the wear coefficient and wear rate present a trend of first decreasing and then increasing. The minimum wear rate of 48.32 × 10⁻⁶ mm³/(N·m) is obtained at the heat treatment duration of 30 min, which is 83.4% lower than that of the untreated sample. Moreover, the optimal corrosion resistance is achieved after 30 min of heat treatment, with the corrosion current density decreasing by 45.8% relative to the as-built specimen. These results demonstrate that heat treatment at 1000 °C for 30 min is an optimal processing parameter to significantly optimize the microstructure and comprehensive performances of LDED-2205 DSS. Full article

(This article belongs to the Special Issue Manufacturing Processes of Metallic Materials (2nd Edition))

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19 pages, 2031 KB

Open AccessArticle

Study of Reductive Leaching of Vanadium from Spent Vanadium Catalysts

by Alma Terlikbaeva, Nazigul Zhumakynbai, Nazira Seidakhmetova, Feruza A. Berdikulova, Abdurassul Zharmenov, Galymzhan Maldybayev, Rustam Sharipov and Makpal Satybayeva

Metals 2026, 16(8), 866; https://doi.org/10.3390/met16080866 - 6 Aug 2026

Abstract

The development of efficient technologies for processing secondary technogenic raw materials represents a promising approach to replenishing vanadium resources. This study investigates the processes of sulfuric acid reductive leaching of vanadium from spent vanadium catalysts using oxalic acid and metallic iron as reducing [...] Read more.

The development of efficient technologies for processing secondary technogenic raw materials represents a promising approach to replenishing vanadium resources. This study investigates the processes of sulfuric acid reductive leaching of vanadium from spent vanadium catalysts using oxalic acid and metallic iron as reducing agents. It was established that oxalic acid provides vanadium extraction of up to 95.2%, whereas the use of metallic iron (2–3 wt.% of the catalyst mass) enables a vanadium recovery rate of 91–92% at a solid-to-liquid ratio of 1:7 and pH 1.3–1.5, offering a more cost-effective alternative. Thermodynamic modeling of the V–Fe–P–SO₄–C₂O₄–H₂O system was performed using the Medusa software package over a pH range of 0–3. The results showed that vanadium(IV) predominantly exists as the VOSO₄ complex in sulfuric acid solutions, whereas the formation of oxalate and phosphate complexes is thermodynamically insignificant. Iron(III) was found to exhibit a strong affinity toward phosphate ions, promoting their selective precipitation as an iron phosphate phase while maintaining vanadium in solution. The obtained results provide a scientific basis for the efficient preliminary separation of iron and vanadium and for improving the selectivity of subsequent vanadium sorption. Full article

(This article belongs to the Section Extractive Metallurgy)

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16 pages, 5615 KB

Open AccessArticle

Research on Method for Contactless Gas-Phase Boron Enrichment of Steels and Alloys Using Powder Boron Sources

by Shunqi Mei, Zekui Hu, Mikhail Guryev, Sergey Ivanov, Alexey Guryev, Sergey Zemlyakov, Guojun Fu and Quan Zheng

Metals 2026, 16(8), 865; https://doi.org/10.3390/met16080865 - 6 Aug 2026

Abstract

Contactless gas-phase boriding is suitable for strengthening the surface of precision steel components because it avoids direct contact between the workpiece and the boriding medium, thereby helping to maintain dimensional accuracy and surface roughness. To address the toxicity, corrosiveness, flammability, and strict gas-handling [...] Read more.

Contactless gas-phase boriding is suitable for strengthening the surface of precision steel components because it avoids direct contact between the workpiece and the boriding medium, thereby helping to maintain dimensional accuracy and surface roughness. To address the toxicity, corrosiveness, flammability, and strict gas-handling requirements associated with externally supplied boron-containing gaseous precursors in conventional gas-phase boriding, this study proposes a novel sealed-container structure for contactless gas-phase boriding, in which powder-filled pockets are distributed along the inner wall of the sealed container, and conducts experimental investigations on gas-phase boriding. Compared with the conventional structure, the modified container places the powder charge in wall-mounted pockets close to the heated container wall, thereby accelerating powder heating. This arrangement also reduced the powder-heating time from approximately 1.1 h to 0.85 h and promoted the earlier generation of an active boron-containing atmosphere, shortening the boriding holding time from 3 h to 1.5 h. Meanwhile, the average boride-layer thickness increased from approximately 54 μm to 117 μm, and the maximum surface microhardness reached 3500 HV. These results indicate that improving the sealed-container structure and optimizing the arrangement of the powder boron source can effectively intensify the contactless gas-phase boriding process. A thick boride diffusion layer can be rapidly formed while maintaining limited dimensional change and acceptable surface roughness. Full article

(This article belongs to the Special Issue Surface Modification and Characterization of Metals and Alloys)

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