Metals

14 pages, 14871 KB

Open AccessArticle

Integrated Valorization of Vanadium–Titanium Magnetite for Recovery of Vanadium-Bearing Molten Iron and Rutile-Rich TiO₂ Product

by Zhengqi Guo, Xing Chen, Deqing Zhu, Jian Pan, Congcong Yang and Siwei Li

Metals 2026, 16(8), 888; https://doi.org/10.3390/met16080888 (registering DOI) - 10 Aug 2026

Abstract

Vanadium–titanium magnetite is a polymetallic resource in which the low reactivity and complex phase constitution of Ti-bearing smelting slag restrict the coordinated recovery of Fe, V, and Ti. In this study, a coupled route involving laboratory-scale induction-furnace smelting separation, magnetic separation, NaOH activation [...] Read more.

Vanadium–titanium magnetite is a polymetallic resource in which the low reactivity and complex phase constitution of Ti-bearing smelting slag restrict the coordinated recovery of Fe, V, and Ti. In this study, a coupled route involving laboratory-scale induction-furnace smelting separation, magnetic separation, NaOH activation roasting, and staged leaching was investigated for upgrading ground vanadium–titanium magnetite metallized pellets. At 1690 °C for 20 min with 2.5 wt% coke under natural slag basicity, a vanadium-bearing metallic product containing 92.07 wt% Fe and 1.27 wt% V was obtained, while Ti was concentrated in a slag containing 47.83 wt% TiO₂. Increasing slag basicity improved vanadium partitioning into the metallic phase but decreased the TiO₂ content and subsequent upgrading performance of the slag. Following magnetic separation and NaOH-activated roasting at 900 °C for 90 min with 40 wt% NaOH, staged leaching yielded a rutile-rich product containing 90.70 wt% TiO₂, with a Ti recovery of 88.75%. These results demonstrate that controlling the phase constitution of smelting-derived Ti-bearing slag is important for its subsequent alkali-activation upgrading and Ti enrichment. Full article

(This article belongs to the Special Issue Green Technologies in Metal Recovery)

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12 pages, 14722 KB

Open AccessArticle

Effect of Nickel Addition on Corrosion Behavior of Laser–Arc Hybrid Welded Al-Mg-Si-Cu Alloy Joints

by Guang Ji and Xiaming Chen

Metals 2026, 16(8), 887; https://doi.org/10.3390/met16080887 (registering DOI) - 10 Aug 2026

Abstract

The corrosion performance of Al-Mg-Si-Cu laser–arc hybrid welded joints modified by 1.8 wt.% Ni remains poorly clarified. In this study, the corrosion behavior was examined via electrochemical measurements combined with SEM, EDS, and SKPFM. Nickel alloying increased the corrosion potential of the α-Al [...] Read more.

The corrosion performance of Al-Mg-Si-Cu laser–arc hybrid welded joints modified by 1.8 wt.% Ni remains poorly clarified. In this study, the corrosion behavior was examined via electrochemical measurements combined with SEM, EDS, and SKPFM. Nickel alloying increased the corrosion potential of the α-Al matrix above that of eutectic Si, thereby suppressing the cathodic role of eutectic Si. Nevertheless, the pronounced potential difference and extensive interfacial area between the Al₃Ni phase and the α-Al matrix promoted localized galvanic corrosion, resulting in chain-like pits along the Al₃Ni phase. This intense galvanic coupling considerably damaged the compactness of the passive film and reduced its resistance. Consequently, the corrosion current density of the welded joint increased significantly from 0.83 μA/cm² to 1.85 μA/cm². These findings suggest that Ni alloying is suitable for welding Al-Mg-Si-Cu alloys in applications where high mechanical performance is essential and corrosion resistance is of secondary importance, such as in body-in-white or chassis load-bearing components. Full article

(This article belongs to the Special Issue Advanced Laser Welding Technology of Alloys)

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14 pages, 11640 KB

Open AccessArticle

Effect of Precipitated Particles on Corrosion Behavior of VCrFeTa_0.1W_0.1 and VCrFeTa_0.2W_0.2 Refractory High-Entropy Alloys

by Weiran Zhang, Zhenbang Wei, Yong Zhang and Jin Li

Metals 2026, 16(8), 886; https://doi.org/10.3390/met16080886 (registering DOI) - 10 Aug 2026

Abstract

In this study, the influence of precipitated Laves particles on the metastable pitting of VCrFeTa_0.1W_0.1 and VCrFeTa_0.2W_0.2 refractory high-entropy alloys (HEAs) in 3.5 wt.% NaCl solution was investigated. Microstructures and corrosion behaviors were characterized by XRD, SEM, [...] Read more.

In this study, the influence of precipitated Laves particles on the metastable pitting of VCrFeTa_0.1W_0.1 and VCrFeTa_0.2W_0.2 refractory high-entropy alloys (HEAs) in 3.5 wt.% NaCl solution was investigated. Microstructures and corrosion behaviors were characterized by XRD, SEM, TEM, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS), and the underlying mechanisms were elucidated. The PDP test results demonstrate that the precipitated Laves particles reduce the pitting resistance of HEAs. The corrosion current densities of VCrFeTa_0.1W_0.1 and VCrFeTa_0.2W_0.2 HEAs are 0.066 and 1.361 μA/cm², respectively, and the pitting potentials are 1.058 and 0.881 V, respectively; that is, reducing the Laves-particle content lowers the corrosion current density by a factor of approximately 20 and raises the pitting potential by approximately 180 mV. The corrosion current density and pitting potential of VCrFeTa_0.1W_0.1 are competitive with those of reported HEAs and traditional alloys. Full article

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12 pages, 4527 KB

Open AccessArticle

Effect of Zn/Mg Ratio on the Microstructure and Coarsening Resistance of Al–Zn–Mg Alloys Aged at 150 °C

by Xueqin Zhang, Xiaolan Wu, Peihao Zhao, Xiangyuan Xiong, Zhi Zheng, Gaoteng Zhang, Shanglong Ao, Guishan Shi, Kunyuan Gao, Wu Wei, Shengping Wen, Hui Huang, Li Rong and Zuoren Nie

Metals 2026, 16(8), 885; https://doi.org/10.3390/met16080885 (registering DOI) - 10 Aug 2026

Abstract

The role of the Zn/Mg ratio in regulating microstructure, precipitation evolution and coarsening resistance in Al–Zn–Mg-based alloys was investigated by microhardness testing, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) during isothermal aging at 150 °C. Three alloy compositions were designed with [...] Read more.

The role of the Zn/Mg ratio in regulating microstructure, precipitation evolution and coarsening resistance in Al–Zn–Mg-based alloys was investigated by microhardness testing, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) during isothermal aging at 150 °C. Three alloy compositions were designed with Zn/Mg ratios of 1.6, 2.4, and 3.9, whereas the combined Zn and Mg level was fixed at 6.0 wt%. All alloys exhibited a typical age-hardening response, whereas the maximum peak hardness was obtained at an intermediate Zn/Mg level rather than at the two extremes. The optimal composition (Zn/Mg = 2.4) reached 137 HV, which is attributable to the formation of the finest precipitates (~3 nm) and the highest number density. Moreover, this alloy exhibited the smallest hardness loss (ΔH = 19 HV) after prolonged aging (192 h). TEM analysis indicated that this alloy exhibited the lowest coarsening rate constant, Kr = 0.43 at 192 h. Furthermore, the variation in Zn/Mg ratio affected grain boundary precipitation, leading to a minimized PFZ width at Zn/Mg = 2.4 while maintaining a similar discontinuous distribution of grain boundary precipitates among the alloys. Overall, tailoring the Zn/Mg balance offers an effective strategy to achieve refined precipitates, improved coarsening resistance, and enhanced mechanical performance with superior thermal stability. Full article

(This article belongs to the Special Issue Innovations in Heat Treatment of Metallic Materials)

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21 pages, 7432 KB

Open AccessArticle

Microstructural and Compositional Analysis of the Ni–Cr–Mo–Nb–Ta Superalloy with High Stability at High Temperatures

by Florentina Niculescu, Mariana-Mirela Stănescu, Gheorghe Iacob, Adrian Emanuel Onici and Lenuta Zidaru

Metals 2026, 16(8), 884; https://doi.org/10.3390/met16080884 (registering DOI) - 9 Aug 2026

Abstract

A multicomponent Ni₅₄Cr₂₈Mo₈Nb₅Ta₅ nickel-based superalloy was produced by vacuum induction melting followed by homogenization, hot forging, solution treatment, and aging to investigate its microstructural and mechanical behavior. The X Ray Fluorescence (XRF) analysis confirmed [...] Read more.

A multicomponent Ni₅₄Cr₂₈Mo₈Nb₅Ta₅ nickel-based superalloy was produced by vacuum induction melting followed by homogenization, hot forging, solution treatment, and aging to investigate its microstructural and mechanical behavior. The X Ray Fluorescence (XRF) analysis confirmed excellent agreement between the nominal and experimental chemical compositions. The X Ray Diffraction(XRD) combined with Rietveld refinement revealed a microstructure dominated by three closely related to face-centered cubic (FCC) (A1) solid-solution regions with slightly different lattice parameters, indicating local compositional variations. The Scanning Electron Microscopy(SEM)/Energy Dispersive Spectroscopy (EDS) observations showed a generally homogeneous elemental distribution, while optical and electron microscopy identified a dendritic microstructure with elongated interdendritic constituents enriched in refractory elements. Mechanical characterization yielded an average hardness of 497 HV_0.5, a compressive strength of approximately 1950 MPa, and room-temperature yield and ultimate tensile strengths of 1050 MPa and 1320 MPa, respectively. Tensile strength gradually decreased with increasing temperature up to 900 °C, while ductility increased from 16% to 25% total elongation. The results indicate that the alloy develops a stable FCC matrix primarily strengthened by solid-solution hardening, with the measured mechanical performance suggesting an additional contribution from precipitation hardening. This study provides an experimental baseline for the development and optimization of conventionally processed Ni–Cr–Mo–Nb–Ta superalloys for high-temperature applications. Full article

(This article belongs to the Section Welding and Joining)

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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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