Metals

38 pages, 4337 KB

Open AccessReview

A Review of Wear-Resistant Coatings for Steel Substrates: Applications and Challenges

by Yanhong Wang, Chao Feng, Tao Lin, Rong Zhu, Jie Zhang, Huapeng Yang, Shanghai Yi, Junlin He, Mingwei Tu and Guangsheng Wei

Metals 2025, 15(11), 1231; https://doi.org/10.3390/met15111231 - 7 Nov 2025

Abstract

This study reviews the current research status and future trends in the field of abrasive-resistant coating preparation, focusing on steel coating technology. The types of materials, preparation methods, and application status of the abrasive-resistant coatings are described in detail. First, the necessity for [...] Read more.

This study reviews the current research status and future trends in the field of abrasive-resistant coating preparation, focusing on steel coating technology. The types of materials, preparation methods, and application status of the abrasive-resistant coatings are described in detail. First, the necessity for an abrasive-resistant coating is analyzed from the perspective of steel applications. Second, abrasive-resistant coating materials of different substrates, including metal-, ceramic-, composite-, and polymer-based materials, are systematically expounded, and the composition, property characteristics, and applications of the materials are systematically discussed. Next, the principles, advantages, and disadvantages of different preparation techniques are analyzed and compared, and the relevant research results are summarized, showing the urgent demand and application prospects of abrasive-resistant coatings. Finally, the performance of the coating is presented, and the development trend of abrasive-resistant coatings on steel surfaces is discussed, providing theoretical support and new ideas for innovation in this field. Full article

(This article belongs to the Special Issue Recent Advances in Surface Modification of Metallic Materials)

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17 pages, 5927 KB

Open AccessArticle

Evaluation of the Possibility of Using Non-Conventional Technological Approaches for the Heat Treatment of Hot-Rolled DP Steel

by Alexandros Banis, Jasmien Flore Arijs and Roumen H. Petrov

Metals 2025, 15(11), 1230; https://doi.org/10.3390/met15111230 - 7 Nov 2025

Abstract

This study investigates the transformation behavior of advanced high-strength dual-phase (DP) steel subjected to thermal cycling, aiming to support improved automotive steel-processing technologies in terms of properties, cost, and speed. The heat treatment applied consisted of 1–7 cycles through the intercritical region at [...] Read more.

This study investigates the transformation behavior of advanced high-strength dual-phase (DP) steel subjected to thermal cycling, aiming to support improved automotive steel-processing technologies in terms of properties, cost, and speed. The heat treatment applied consisted of 1–7 cycles through the intercritical region at a conventional heating rate. Results were compared with the conventional dual-phase steel treatment currently used in industry, as well as with variants that combine thermal cycling and fast heating, the latter offering potential for carbon-free methods. The goal is to gain a deeper understanding of the transformations that occur in the material and the potential benefits that may result. Characterization was performed using dilatometry, electron microscopy techniques, and Vickers hardness testing. Findings show the initial ferrite–martensite microstructure remained largely unchanged after cycling, though preferential austenite nucleation within ferrite and Mn segregation remained. The resulting microstructure consisted of ferrite, bainite, martensite, and retained austenite. Crystallographic orientation analysis revealed texture memory effects, with preferred orientations persisting after multiple cycles. Grain refinement occurred mainly in transformed zones, while ferrite showed slight growth with more cycles, correlating with a reduced bainite/martensite fraction. Hardness increased significantly after the first cycle but declined with subsequent cycles, reflecting a reduction in bainite/martensite fraction. It is found that when up to two cycles are used, the process can be beneficial for the steel properties; otherwise, other alternatives, such as fast heating, can be applied to optimize production. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Metallic Materials Under Heat Treatment)

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22 pages, 11106 KB

Open AccessArticle

Differences in Yield Behavior in the Thickness Direction of TMCP-Processed HSLA Thick Steel Plates and the Evolution of Microstructure Property Gradients

by Chuxiao Qu, Wenliang Lu, Han Su and Mengqi Zhu

Metals 2025, 15(11), 1229; https://doi.org/10.3390/met15111229 - 7 Nov 2025

Abstract

Thick steel plates in bridges exhibit mechanical property gradients along their thickness, yet the underlying micro-mechanisms remain unclear. This study investigates an 80 mm thick 420 MPa-grade HSLA steel plate, and also quantitatively investigates the mechanism of its mechanical gradient behavior in the [...] Read more.

Thick steel plates in bridges exhibit mechanical property gradients along their thickness, yet the underlying micro-mechanisms remain unclear. This study investigates an 80 mm thick 420 MPa-grade HSLA steel plate, and also quantitatively investigates the mechanism of its mechanical gradient behavior in the thickness direction through layered tensile tests combined with multi-scale microstructural characterization. The unique contribution of this work lies in establishing a quantitative correlation between the gradient in the dislocation density and the transition in yielding behavior. The results show that the surface layer area of the tested steel exhibited continuous yield characteristics, while all core layers exhibited pronounced discontinuous yielding. The mechanical properties showed a gradient distribution along the thickness direction, with the yield strength and tensile strength decreasing from 512.4 MPa and 545.9 MPa at the surface to 419.5 MPa and 520.4 MPa at the center (1/2t). Microstructural analysis shows that the full-thickness structure was composed of granular bainite (GB) and polygonal ferrite (PF). With respect to increases with depth, the average grain size increased from 6.86 µm at the surface to 11.57 µm at the center. Moreover, the surface region exhibited a broader grain size distribution range and higher size dispersity. The second-phase precipitates in the full thickness were mainly of two types, namely, Fe₃C and (Nb, Ti) (C, N) composite precipitates, and the precipitates in the surface layer had smaller sizes and higher distribution densities. Crucially, the dislocation density decreased sharply from the surface to 1/8t, then stabilized. While quantitatively elucidating the contributions of various strengthening mechanisms to the strength gradient, the mechanistic analysis also reveals a dislocation microstructure synergistic mechanism underlying the yield behavior differences. Full article

(This article belongs to the Special Issue Metallic Materials Behaviour Under Applied Load)

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20 pages, 30027 KB

Open AccessArticle

New Model for Estimating the Volume of Martensite Transformed Using Acoustic Emission Measurements During an Induction Hardening Process

by Erlantz Sola Llanos, Rafael Rodríguez, Marcos Aguirre, Carmelo Javier Luis-Pérez and Mario Javier Cabello

Metals 2025, 15(11), 1228; https://doi.org/10.3390/met15111228 - 7 Nov 2025

Abstract

The accurate detection and quantification of martensitic transformation in steel during quenching are essential for controlling the resulting material properties. Numerous studies have investigated this phenomenon using Acoustic Emission (AE) techniques, owing to the significant energy release associated with the transformation. However, no [...] Read more.

The accurate detection and quantification of martensitic transformation in steel during quenching are essential for controlling the resulting material properties. Numerous studies have investigated this phenomenon using Acoustic Emission (AE) techniques, owing to the significant energy release associated with the transformation. However, no model based on acoustic emission currently exists that can estimate the martensite volume formed during induction hardening. In this work, a novel model is proposed to estimate the transformed martensite volume in induction hardening treatment, focused on the material, geometry, and AE settings used. By integrating acoustic emission data with conventional Vickers hardness measurements, the model parameters can be calibrated. Induction quenching experiments were carried out on cylindrical 42CrMo4 (AISI 4140) steel bars equipped with acoustic emission sensors to capture transformation-related events during heat treatment. The martensite volume after quenching was estimated from hardness values. Model calibration using the experimental acoustic emission data and martensite volume demonstrated strong agreement between predictions and experimental observations. The proposed model offers the potential for in-process monitoring of induction quenching, thereby reducing reliance on conventional characterization techniques. Full article

(This article belongs to the Special Issue Surface Treatments and Coating of Metallic Materials)

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29 pages, 2026 KB

Open AccessReview

Hydrometallurgical Recovery Technology for Rare Earth and Iron Separation from Spent NdFeB Magnets

by Mingyan Cheng, Liqing Li, Yanfei Xiao and Helian Liu

Metals 2025, 15(11), 1227; https://doi.org/10.3390/met15111227 - 7 Nov 2025

Abstract

The recovery of rare earth elements (REEs) from the spent NdFeB magnets has great strategic significance for ensuring the security of critical mineral resources. This process requires scientifically designed separation technologies to ensure high output and purity of the obtained rare earths. Hydrometallurgy [...] Read more.

The recovery of rare earth elements (REEs) from the spent NdFeB magnets has great strategic significance for ensuring the security of critical mineral resources. This process requires scientifically designed separation technologies to ensure high output and purity of the obtained rare earths. Hydrometallurgy has been widely applied to extract REEs from spent permanent magnets. This paper summarizes and reviews hydrometallurgical technologies, mechanisms, and applications for the separation and recovery of REEs and iron (Fe) from the spent permanent magnets. Key methods include: The hydrochloric acid total solution method, where the spent NdFeB is completely dissolved in hydrochloric acid, iron is precipitated and removed, and then REEs are extracted. The hydrochloric acid preferential dissolution method, where spent NdFeB magnets are first fully oxidized by oxidative roasting, converting Fe²⁺ to Fe³⁺, which hydrolyzes to Fe(OH)₃, and is precipitated and removed, allowing for the subsequent extraction of REEs to obtain rare earth oxides. Acid baking and water leaching, where spent NdFeB is calcined with acidification reagents, and the calcined products are dissolved in water to leach out REEs. At the same time, Fe is retained in the leaching residue. Electrolysis in aqueous solution, where Fe is electrolyzed at the anode or deposited at the cathode to separate it from REES. Organic acids leaching, where organic acids dissolve metals through acidolysis and complexation. Bioleaching, which utilizes microorganisms to recover metal through biological oxidation and complexation. Ionic liquid systems, where Fe or REEs are extracted using ionic liquid or leached by deep eutectic solvents. This paper provides an in-depth discussion on the challenges, advantages, and disadvantages of these strategies for recycling spent NdFeB magnets, as well as the leaching and extraction behavior of REEs. It focuses on environmental impact assessment, improving recovery efficiency, and decreasing reagent consumption. The future development direction for recycling spent NdFeB magnets is proposed, and a research idea of proposing a combined process to avoid the drawbacks of a single recycling method is introduced. Full article

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15 pages, 2708 KB

Open AccessArticle

Numerical Simulation of the Differential Influence of Work Roll and Intermediate Roll Profiles on Strip Shape

by Yujin Liu, Hongbo Li, Xuechang You and Hairui Zhao

Metals 2025, 15(11), 1226; https://doi.org/10.3390/met15111226 - 6 Nov 2025

Abstract

This study employs the UCMW (Universal crown mill with work roll shifting) cold rolling mill as the research object, focusing on the critical process parameter of single-taper profiles for both the work roll and intermediate roll. By establishing an integrated finite element model [...] Read more.

This study employs the UCMW (Universal crown mill with work roll shifting) cold rolling mill as the research object, focusing on the critical process parameter of single-taper profiles for both the work roll and intermediate roll. By establishing an integrated finite element model of the roll-strip system, this analysis examines the influence patterns of single-taper profiles applied to the work roll, the intermediate roll, and their combined configuration on strip shape. The research demonstrates that when the work roll utilizes a single-taper profile, the strip shape approximates a rectangular profile at a shift amount of −75 mm and exhibits a concave profile at −95 mm. For the intermediate roll employing a single-taper profile, the strip shape manifests a convex profile within the shift range of −150 mm and transitions to an M-shape at −180 mm. Utilizing the combined roll profiles induces a gradual transition in strip shape from convex to concave within the shift range of −50 mm to −95 mm. Comparative analysis indicates that at a shift of −50 mm, the combined roll profiles yield a shape closer to rectangular; at −75 mm, the work roll profile produces superior results; at −95 mm, both the work roll profile and the combined profiles result in concave shapes, with the combined configuration exerting the most pronounced effect. This investigation furnishes a theoretical foundation for roll profile optimization in rolling mills and the enhancement of strip dimensional precision. Full article

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23 pages, 5721 KB

Open AccessArticle

An Investigation into the Influence of Weld Bead Sequence on Residual Stress Distribution in a High-Speed Train Bogie Beam Using Thermo-Elastic–Plastic Finite Element Analysis

by Gaojian Wang, Zhixu Mao, Chenyang Zhou, Zuoshi Yang, Yifeng Wang and Dean Deng

Metals 2025, 15(11), 1225; https://doi.org/10.3390/met15111225 - 6 Nov 2025

Abstract

The bogie serves as a critical structural component in high-speed trains, subjected to dynamic loads throughout its operational lifecycle. Enhancing the fatigue life of the bogie necessitates not only ensuring welding quality but also effectively managing welding residual stresses during the manufacturing process. [...] Read more.

The bogie serves as a critical structural component in high-speed trains, subjected to dynamic loads throughout its operational lifecycle. Enhancing the fatigue life of the bogie necessitates not only ensuring welding quality but also effectively managing welding residual stresses during the manufacturing process. In this study, an efficient and simplified thermal–elastoplastic finite element method was developed based on the ABAQUS software platform, and its reliability and applicability were validated through comparison with measured data. The computational approach was employed to investigate the distribution characteristics of welding residual stresses in a weathering steel bogie beam, with particular emphasis on the influence of different welding sequences on residual stress distribution. Simulated results demonstrate that the welding sequence significantly influences the residual stress distribution and magnitude within the beam. The numerical simulation methodology developed in this study offers a powerful tool for optimizing welding sequences to regulate residual stresses during the fabrication of bogie structures. Full article

(This article belongs to the Special Issue Hybrid Additive Manufacturing and Welding for Metal Alloys: Advances and Applications)

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13 pages, 4511 KB

Open AccessArticle

Optimization of Microstructure and Strength–Ductility Synergy in Selective Laser-Melted Ti6Al4V Alloy via Chessboard Scanning Strategy

by Haochun Zhang, Chilan Cai, Liang Yan, Hailin Gong and Jin Yang

Metals 2025, 15(11), 1224; https://doi.org/10.3390/met15111224 - 5 Nov 2025

Abstract

To optimize the microstructure and mechanical properties of Ti6Al4V alloys fabricated via Selective Laser Melting (SLM), this study proposes an optimization approach based on the chessboard scanning strategy. A systematic comparison of three scanning strategies—alternating, stripe, and chessboard scanning—was conducted to examine their [...] Read more.

To optimize the microstructure and mechanical properties of Ti6Al4V alloys fabricated via Selective Laser Melting (SLM), this study proposes an optimization approach based on the chessboard scanning strategy. A systematic comparison of three scanning strategies—alternating, stripe, and chessboard scanning—was conducted to examine their effects on thermal input distribution, grain refinement, phase composition, and mechanical performance. Characterization results from Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD), and Transmission Electron Microscopy (TEM) revealed that the chessboard scanning strategy effectively refines the grain size to 88.64 ± 10.79 μm and increases the strengthening phase α′ content to 53.3%. Mechanical testing showed a tensile strength of 1179 ± 17 MPa (11.02% higher than stripe scanning) and elongation of 7.9 ± 0.4%. This strategy promotes random grain orientation by altering the scanning path, disrupting directional solidification, and suppressing texture formation. Microstructural mechanism analysis suggests that dislocation strengthening, increased α′ content, and grain refinement synergistically enhance both strength and ductility. These findings provide theoretical support for optimizing SLM parameters and the design of Ti6Al4V alloys’ microstructure and mechanical properties. Full article

(This article belongs to the Special Issue Additive Manufacturing and Characterization of Metallic Alloys and Composites)

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22 pages, 6316 KB

Open AccessArticle

Research on the Neutral Layer Deflection Phenomenon in Three-Dimensional Stretch Bending of Profiles

by Songyue Yang, Yu Wen, Hao Sun, Yi Li and Ce Liang

Metals 2025, 15(11), 1223; https://doi.org/10.3390/met15111223 - 5 Nov 2025

Abstract

This paper aims to study the deflection phenomenon of the neutral layer in the cross-section of profiles during the 3D stretch-bending process. By establishing the displacement field for both the stretching and bending processes of a profile with elastoplastic constitutive characteristics, and combining [...] Read more.

This paper aims to study the deflection phenomenon of the neutral layer in the cross-section of profiles during the 3D stretch-bending process. By establishing the displacement field for both the stretching and bending processes of a profile with elastoplastic constitutive characteristics, and combining the deformation processes, the geometric description of the profile deformation is constructed, and then linearized. Subsequently, by integrating the material’s constitutive properties and model boundary conditions, the analytical model parameters for profiles with regular cross-sections are solved. The analytical model effectively captures the behavior of the neutral layer and its deflection phenomenon. To further investigate, the finite element model was developed to simulate the deformation process. The distribution of the neutral layer in the simulation results matched the analytical predictions. To generalize the analytical results to profiles with arbitrary cross-sections, an L-shaped profile was analyzed, and a roller-based 3D flexible stretch-bending device with roller dies was used. By measuring the springback direction, the neutral layer deflection observed in both the analytical and finite element model results was validated. The results demonstrate that, under small deformation conditions, the neutral layer deflection during the 3D stretch-bending process was successfully predicted. Full article

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21 pages, 7853 KB

Open AccessArticle

The Effect of Surface Corrosion Damage and Fe Content on the Fatigue Life of an AlSi7Mg0.6 Cast Alloy Used in the Electric Automotive Industry

by Lenka Kuchariková, Eva Tillová, Zuzana Šurdová, Mária Chalupová, Viera Zatkalíková, Edita Illichmanová and Ivana Švecová

Metals 2025, 15(11), 1222; https://doi.org/10.3390/met15111222 - 5 Nov 2025

Abstract

The aluminum casting alloy AlSi7Mg0.6 (A357) is extensively used in the automotive industry due to its favorable balance of mechanical properties, castability, lightweight characteristics, and corrosion resistance. Castings made from this alloy are often subjected to harsh service environments, where surface degradation and [...] Read more.

The aluminum casting alloy AlSi7Mg0.6 (A357) is extensively used in the automotive industry due to its favorable balance of mechanical properties, castability, lightweight characteristics, and corrosion resistance. Castings made from this alloy are often subjected to harsh service environments, where surface degradation and microstructural variability can significantly impact fatigue performance. This study investigates the combined effects of surface corrosion damage and higher Fe content on the fatigue life of the AlSi7Mg0.6 alloy, using a rotating bending fatigue test under simultaneous corrosion exposure in a 3.5 wt. % NaCl solution. The effect of corrosion and Fe content on fatigue life was then investigated and analyzed using Wöhler curves and scanning electron microscopy (SEM). The results demonstrate that the corrosion-fatigue interaction accelerated the kinetics of the fatigue process, while the fracture mechanism and crack initiation places are not fundamentally altered compared to alloys in the state without corrosion damage. A comparison of the fatigue lifetime of samples in an air environment and a corrosive environment shows that the corrosive environment (3.5% NaCl) reduces the fatigue lifetime of alloys without T6 by an average of 7.5 MPa and alloys after T6 by 6 MPa. The results are probably due to the penetration of chloride ions into casting defects located on the surface of the samples. Surface pits formed during corrosion act as stress concentrators, increasing the likelihood of stress-induced failure. Microstructural feature morphology, especially Fe-rich intermetallic phases, influences crack propagation mechanisms. Full article

(This article belongs to the Special Issue Advances in Microstructure and Properties of Light Alloys)

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15 pages, 2173 KB

Open AccessArticle

Application of Machine Learning and Data Augmentation Algorithms in the Discovery of Metal Hydrides for Hydrogen Storage

by Giancarlo Beltrame, Erika Michela Dematteis, Vitalie Stavila, Paola Rizzi, Marcello Baricco and Mauro Palumbo

Metals 2025, 15(11), 1221; https://doi.org/10.3390/met15111221 - 4 Nov 2025

Abstract

The development of efficient and sustainable hydrogen storage materials is a key challenge for realizing hydrogen as a clean and flexible energy carrier. Among various options, metal hydrides offer high volumetric storage density and operational safety, yet their application is limited by thermodynamic, [...] Read more.

The development of efficient and sustainable hydrogen storage materials is a key challenge for realizing hydrogen as a clean and flexible energy carrier. Among various options, metal hydrides offer high volumetric storage density and operational safety, yet their application is limited by thermodynamic, kinetic, and compositional constraints. In this work, we investigate the potential of machine learning (ML) to predict key thermodynamic properties—equilibrium plateau pressure, enthalpy, and entropy of hydride formation—based solely on alloy composition using Magpie-generated descriptors. We significantly expand an existing experimental dataset from ~400 to 806 entries and assess the impact of dataset size and data augmentation, using the PADRE algorithm, on model performance. Models including Support Vector Machines and Gradient Boosted Random Forests were trained and optimized via grid search and cross-validation. Results show a marked improvement in predictive accuracy with increased dataset size, while data augmentation benefits are limited to smaller datasets and do not improve accuracy in underrepresented pressure regimes. Furthermore, clustering and cross-validation analyses highlight the limited generalizability of models across different material classes, though high accuracy is achieved when training and testing within a single hydride family (e.g., AB₂). The study demonstrates the viability and limitations of ML for accelerating hydride discovery, emphasizing the importance of dataset diversity and representation for robust property prediction. Full article

(This article belongs to the Section Metallic Functional Materials)

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19 pages, 11365 KB

Open AccessArticle

Hot Deformation Behavior and Dynamic Recrystallization Mechanism of GH3230 Superalloy

by Shichong Yuan, Yanhui Liu, Hua Zhang, Hao Li, Qing Li and Jinshan Li

Metals 2025, 15(11), 1220; https://doi.org/10.3390/met15111220 - 4 Nov 2025

Abstract

An isothermal hot compression test of GH3230 was carried out under deformation conditions with deformation temperatures ranging from 1020 to 1110 °C and strain rates ranging from 1 to 0.001 s⁻¹. On this basis, the corresponding constitutive equation of the alloy [...] Read more.

An isothermal hot compression test of GH3230 was carried out under deformation conditions with deformation temperatures ranging from 1020 to 1110 °C and strain rates ranging from 1 to 0.001 s⁻¹. On this basis, the corresponding constitutive equation of the alloy was established.

\dot{ε} = e x p (36.123) {[s i n h (0.00587 σ)]}^{4.7946} e x p [- 451.507 / (R T)]

. At the same time, a power dissipation diagram and thermal processing diagram were created. The peak value η can reach 0.36, and the optimum hot working parameter window of the GH3230 superalloy is 1020~1110 °C/0.1~0.001 s⁻¹. The microstructure evolution of the alloy under different conditions was studied by EBSD. With an increase in deformation temperature and a decrease in strain rate, the grain size significantly improved; the average grain size of the GH3230 alloy increased from 16.86 to 35.06 μm, and the degree of recrystallization of the alloy also improved. The maximum recrystallization volume fraction is 75.2%. At low temperature and high strain rate, the recrystallization mechanism of the microstructure is mainly CDRX, and DDRX is the auxiliary mechanism. At high temperature and low strain rate, the main corresponding recrystallization mechanism gradually transforms into DDRX. Full article

(This article belongs to the Special Issue Deformation Behavior and Microstructure Evolution of Alloys)

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24 pages, 14236 KB

Open AccessArticle

Ni-Based Coatings on Molybdenum: Influence of Current Density and Basalt on Mechanical Properties and Forensic Relevance

by Ivana O. Mladenović, Vladislav Jovanov, Željko Radovanović, Vera Obradović, Rastko Vasilić, Radmila Jančić-Heinemann and Nebojša D. Nikolić

Metals 2025, 15(11), 1219; https://doi.org/10.3390/met15111219 - 2 Nov 2025

Abstract

Ni and Ni/basalt (Ni/Bst) coatings prepared by the electrodeposition on Mo substrate were analyzed with the aim of their potential application in forensics. The coatings of Ni and Ni/Bst are produced galvanostatically from the sulfamate electrolyte at different current densities and characterized by [...] Read more.

Ni and Ni/basalt (Ni/Bst) coatings prepared by the electrodeposition on Mo substrate were analyzed with the aim of their potential application in forensics. The coatings of Ni and Ni/Bst are produced galvanostatically from the sulfamate electrolyte at different current densities and characterized by scanning electron microscope (morphology), X-ray diffraction (structure) and Vickers microindentation (microhardness). The wettability of Ni and Ni/Bst coatings was also investigated. While morphology and microhardness of the coatings strongly depended on the current density of electrodeposition and the presence of basalt particles in the electrolyte, the effect of basalt addition on structure of the coatings was not observed. The microhardness of Ni coatings was in the (1.6951–5.7246) GPa range, while the addition of basalt particles increased the range to (5.8206–10.7981) GPa. Both Ni and Ni/Bst coatings were hydrophilic, whereas comparison of the coatings obtained at the same current density showed that incorporation of the basalt particles in the coating decreases the degree of hydrophilicity, as observed by the increase in the water contact angle (WCA). The largest WCA, i.e., the smallest hydrophilicity, showed Ni/Bst coating produced at 30 mA cm⁻² (WCA ≈ 75.5°), and was about 46.7% larger than that of Mo substrate (WCA ≈ 51.5°). This coating also showed the best development of latent fingerprints with clearly visible ridge details, indicating that there is strong correlation between fingerprint development and the wettability of the coatings. Full article

(This article belongs to the Section Powder Metallurgy)

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17 pages, 7777 KB

Open AccessArticle

Microstructure and Properties of TA2 Titanium Joints Brazed with Ti–Zr–Cu–Ni Filler Metal

by Zimeng Xiao, Huiling Zhou, Sheng Lu, Zexin Wang and Oleksandr Dobuvyy

Metals 2025, 15(11), 1218; https://doi.org/10.3390/met15111218 - 2 Nov 2025

Abstract

TA2 titanium was brazed with a Ti–37.5Zr–15Cu–10Ni filler metal at 860–890 °C for 20 min to investigate the influence of temperature on joint properties. Raising the brazing temperature reduced residual filler in the seam center and transformed the microstructure from heterogeneous phases to [...] Read more.

TA2 titanium was brazed with a Ti–37.5Zr–15Cu–10Ni filler metal at 860–890 °C for 20 min to investigate the influence of temperature on joint properties. Raising the brazing temperature reduced residual filler in the seam center and transformed the microstructure from heterogeneous phases to a uniform α-(Ti,Zr) solid-solution matrix, accompanied by significant widening of the diffusion layer. At brazing temperatures of 890 °C, the hardness decreased to below 300 HV_0.5 and became more uniform as brittle phases were suppressed. The shear strength reached a maximum of 302 MPa, and the fracture morphology exhibited characteristics of ductile fracture. Micro-electrochemical testing indicated that the joint brazed exhibited an almost uniform current distribution and significantly reduced localized corrosion. Although a small fraction of the Widmanstätten structure was observed at this temperature, it did not impair the overall mechanical performance. These findings demonstrate that a moderate increase in brazing temperature promotes elemental diffusion, alleviates brittle phase enrichment, and markedly enhances the mechanical properties and corrosion resistance of TA2 joints. Full article

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16 pages, 3917 KB

Open AccessArticle

The Effect of In-Situ-Grown Graphene from Highland Barley Powder on the Properties of Copper Matrix Materials

by Zhe Wang, Changfei Sun, Xianglongtian Tang, Cheng Du, Denghui Li and Cong Chen

Metals 2025, 15(11), 1217; https://doi.org/10.3390/met15111217 - 2 Nov 2025

Abstract

In situ graphene was grown on the surface of copper particles using highland barley powder, which is rich in sucrose and β-glucan, as a carbon source. The graphene content in the graphene-coated copper (Gr@Cu) composite powder was 4.98 wt.%. A characteristic angle of [...] Read more.

In situ graphene was grown on the surface of copper particles using highland barley powder, which is rich in sucrose and β-glucan, as a carbon source. The graphene content in the graphene-coated copper (Gr@Cu) composite powder was 4.98 wt.%. A characteristic angle of approximately 14° was observed between the graphene and copper crystal planes, indicating strong interfacial bonding. Raman spectroscopy revealed an ID/IG ratio of 0.96 for the graphene. Owing to the in situ growth of graphene, the mechanical properties of the copper matrix are effectively strengthened. At a graphene content of 0.7 wt.%, the graphene was uniformly dispersed within the copper matrix, resulting in optimized mechanical properties of the composite. This composite exhibited a conductivity of 70% IACS and a compressive yield strength of 175 MPa. Full article

(This article belongs to the Section Powder Metallurgy)

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13 pages, 11164 KB

Open AccessArticle

Synergistic Effects of Sub-Micron WC Reinforcement and T6 Heat Treatment on the Evolution of Microstructure and Mechanical Behavior in Al–Cu–Mg Composites Fabricated Through Powder Metallurgy

by Gustavo Rodríguez-Cabriales, Juan Pablo Flores-De los Ríos, Juan Francisco López de Lara-Herrera, Mario Sánchez-Carrillo, Hansel Manuel Medrano Prieto, Jose Manuel Mendoza-Duarte, Marco Antonio Ruiz-Esparza-Rodríguez, Carlos Gamaliel Garay-Reyes, Sergio González, Alfredo Martínez-García, Ivanovich Estrada-Guel and Roberto Martínez-Sánchez

Metals 2025, 15(11), 1216; https://doi.org/10.3390/met15111216 - 1 Nov 2025

Abstract

Al–Cu–Mg composites reinforced with sub-micron tungsten carbide (WC) particles were synthesized by powder metallurgy and subjected to T6 heat treatment to clarify the interplay between dispersion strengthening and precipitation hardening. Composites with 1–3 wt.% WC (average size 0.8 μm) were solution-treated at 540 [...] Read more.

Al–Cu–Mg composites reinforced with sub-micron tungsten carbide (WC) particles were synthesized by powder metallurgy and subjected to T6 heat treatment to clarify the interplay between dispersion strengthening and precipitation hardening. Composites with 1–3 wt.% WC (average size 0.8 μm) were solution-treated at 540 °C for 3 h, water-quenched, and aged at 195 °C for up to 100 h. Microstructural analyses confirmed a uniform distribution of WC and demonstrated that its presence did not modify the dissolution–precipitation sequence of the Al-Cu-Mg matrix. Transmission Electron Microscopy observations provided direct evidence of θ′ (Al₂Cu) precipitates. The 3 wt.% WC composite reached peak hardness after 5 h (78 HRF), a 15% increase over the T6-treated unreinforced alloy, and exhibited a 40% higher yield strength (330 MPa). These improvements were attributed to the combined effects of Orowan strengthening and age-hardening precipitates (θ′). The results demonstrate that integrating powder metallurgy, sub-micron WC reinforcement, and T6 treatment is an effective route to enhance strength in Al–Cu–Mg alloys without delaying aging kinetics. Full article

(This article belongs to the Special Issue Synthesis, Microstructure, and Properties of Lightweight Metal Matrix Composite Materials)

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43 pages, 8258 KB

Open AccessArticle

Optimizing the Leaching Parameters of Asbestos Tailings for Maximizing the Recovery of Critical Metals

by Zouhour Rajah, Daphne Freda Gavras, Herizo Andrianandraina, Fariborz Faraji, Mahamadou Traoré, Stéphanie Somot, Faïçal Larachi, Dominic Ryan and Ahmed Bouajila

Metals 2025, 15(11), 1215; https://doi.org/10.3390/met15111215 - 1 Nov 2025

Abstract

Asbestos tailings represent a historical liability in many countries. Canada aims at transforming this industrial legacy into an opportunity to both mitigate the environmental footprint and recover critical (such as magnesium, nickel, chromium, and cobalt) and strategic metals, which represent significant economic development [...] Read more.

Asbestos tailings represent a historical liability in many countries. Canada aims at transforming this industrial legacy into an opportunity to both mitigate the environmental footprint and recover critical (such as magnesium, nickel, chromium, and cobalt) and strategic metals, which represent significant economic development potential. This study aimed to investigate the recovery of critical and strategic metals (CSMs) from asbestos tailings using hydrochloric (HCl) acid leaching, with acid concentration (2–12 mol/L), leaching temperature (20–90 °C), and solid–liquid ratio (10–40%) as key process parameters. The tailing samples studied is composed mostly of chrysotile and lizardite. It contains about 40% magnesium (as its oxide MgO) and nickel and chromium showing contents 52 and 60 times higher than their respective average crustal abundances (Clarke values). Iron content is 8.7% (expressed as its ferric oxide Fe₂O₃). To optimize key factors influencing the leaching process, a statistical experimental design was employed. The designed leaching experiments were subsequently performed, and results were used to define leaching conditions aiming at maximizing Mg and Ni recoveries while minimizing iron contamination using response surface methodology (RSM) based on the central composite design (CCD). A quadratic polynomial model was developed to describe the relationship between the process parameters and metal recoveries. Among the tested effects of acid concentration, temperature, and pulp density on magnesium recovery, the modeling indicated that both hydrochloric acid concentration and leaching temperature significantly enhanced metal recovery, whereas increasing pulp density had a negative effect at low temperature. The empirical mathematical model derived from the experimental data, accounting for the uncertainties on chemical data, indicated that high magnesium recovery was achieved at 90 °C, with 10–12 N hydrochloric acid and a solid-to-liquid ratio of 33.6–40%. These findings reveal the potential for the recovery of critical and strategic metals, both in terms of efficiency and economic viability. Full article

(This article belongs to the Special Issue Leaching, Separation and Purification of Metals from Secondary Resources)

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15 pages, 5771 KB

Open AccessArticle

Influence of Cooling Process on Microstructure and Mechanical Properties of High-Strength, High-Ductility Ship Plate Steel

by Xiaoguang Zhou, Yongling Shao, Xuyuan Zhang, Weina Zhang, Siwei Wu, Guangming Cao and Zhenyu Liu

Metals 2025, 15(11), 1214; https://doi.org/10.3390/met15111214 - 1 Nov 2025

Abstract

This study investigated the influence of the cooling process on the microstructure and mechanical properties of high-strength, high-ductility ship plate steel. The transformation temperature ranges for ferrite (F) and bainite (B) for the experimental steel were determined through thermal simulation experiments. Based on [...] Read more.

This study investigated the influence of the cooling process on the microstructure and mechanical properties of high-strength, high-ductility ship plate steel. The transformation temperature ranges for ferrite (F) and bainite (B) for the experimental steel were determined through thermal simulation experiments. Based on these findings, hot-rolling experiments in laboratory were designed to elucidate the influence of three different cooling paths on the resultant microstructure and mechanical properties. The results demonstrate that the two-stage (air cooling + water cooling) and three-stage (water cooling + air cooling + water cooling) processes after rolling enhance the strength through phase transformation and precipitation strengthening mechanisms. The three-stage process provides an additional fine-grain strengthening effect. Compared to the F+Pearlite (P) or B microstructures produced by single-stage cooling, the F+B dual-phase steel obtained through these multi-stage cooling routes exhibits superior ductility at a comparable yield strength grade. Notably, the two-stage cooling mode proves particularly effective in enhancing ductility. These findings provide a theoretical foundation for designing cooling processes for high-strength, high-ductility ship plate steel. Full article

(This article belongs to the Special Issue Research on Microstructure and Performance Mechanisms of Advanced Steels and Alloys)

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21 pages, 8013 KB

Open AccessArticle

Analysis of Microstructure Evolution, Mechanical Properties, and Strengthening Mechanisms in Extruded 2014Al-GNP Composites

by Junjie Xiong, Shaolong Ma, Jinsheng Zhou and Yu Zhou

Metals 2025, 15(11), 1213; https://doi.org/10.3390/met15111213 - 31 Oct 2025

Abstract

A 2014Al matrix composite reinforced with 0.8 wt.% graphene nanoplatelets (GNPs) was prepared by pre-dispersion and ultrasonic melt casting. Subsequently, the as-cast 2014Al-GNP composite was subjected to hot extrusion under different parameters, followed by a comparative analysis of the microstructure and properties of [...] Read more.

A 2014Al matrix composite reinforced with 0.8 wt.% graphene nanoplatelets (GNPs) was prepared by pre-dispersion and ultrasonic melt casting. Subsequently, the as-cast 2014Al-GNP composite was subjected to hot extrusion under different parameters, followed by a comparative analysis of the microstructure and properties of the various alloys. Microstructure and phase composition of the prepared samples were characterized using OM, SEM, EDS, EBSD and TEM inspections. The results indicate that the addition of GNPs effectively promoted the refinement of the as-cast matrix alloy microstructure, while hot extrusion with appropriate parameters further refined the microstructure of the as-cast matrix alloy. At an extrusion ratio of 16, the Al₂Cu, Al₂CuMg, and GNPs in the microstructure displayed a band-like distribution along the extrusion direction, with reduced size and enhanced uniformity. Concurrently, the dislocation density and Kernel Average Misorientation (KAM) values of the composite increased significantly, dynamic recrystallization intensified, and the texture was further enhanced. The tensile strength reached 572.1 MPa, hardness was 369.6 HV, and elongation was 11.9%, representing improvements of 89.0%, 92.0%, and 142.9%, respectively, compared to the as-cast matrix alloy. Fracture surface analysis exhibited brittle fracture characteristics in the matrix alloy, while the extruded composite with optimal parameters displayed distinct ductile fracture features. In the extruded aluminum matrix composite, the interface between GNPs and the matrix was clean, with mutual diffusion of Al and C atoms, achieving an excellent interfacial bonding state. The significant enhancement in mechanical properties of the extruded alloy was primarily attributed to grain refinement strengthening, dislocation strengthening, and load transfer strengthening by GNPs. Full article

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