Metals

26 pages, 2570 KB

Open AccessReview

Research Status on the Corrosion Resistance and Protective Coating Technologies of Mg-Rare Earth Alloys

by Yueyue Yang, Yufeng Chen, Haoran Hong, Hongliang Zhang, Teng Liu and Zhisheng Nong

Metals 2026, 16(9), 993; https://doi.org/10.3390/met16090993 (registering DOI) - 5 Sep 2026

Mg alloys are among the lightest metallic structural materials used in engineering applications, possessing a range of favorable properties and holding broad application prospects. However, the corrosion resistance of Mg alloys is relatively poor compared to other metallic structural materials, which limits their [...] Read more.

Mg alloys are among the lightest metallic structural materials used in engineering applications, possessing a range of favorable properties and holding broad application prospects. However, the corrosion resistance of Mg alloys is relatively poor compared to other metallic structural materials, which limits their use in various working environments. The addition of rare earth elements is one approach to improving the corrosion resistance of Mg alloys; nevertheless, the corrosion resistance of Mg-rare earth alloys still falls short of industrial application requirements. This paper aims to introduce the corrosion resistance of Mg-rare earth alloys and their applied protective coatings. Through coating characterization techniques, the protective effects of coatings on Mg-rare earth alloys are analyzed and elucidated. Finally, a summary and outlook on the corrosion resistance of Mg-rare earth alloys and coating protection technologies are provided. Full article

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22 pages, 21002 KB

Open AccessArticle

Weldability of Cold-Roll-Bonded Fe–Al Clad Sheets in Dissimilar Joining: Effects of Sheet Configuration and Internal Steel-Layer Melting

by Seung Cheol Shin, Yong Kim, Hye Chan Park and Hyun Jin Woo

Metals 2026, 16(9), 992; https://doi.org/10.3390/met16090992 - 4 Sep 2026

Abstract

Cold-roll-bonded (CRB) Fe–Al clad sheets, which incorporate an internal steel layer within the clad structure, are candidate materials for dissimilar joining in lightweight structural applications, yet systematic comparisons of their weldability across multiple joining processes remain limited. This study evaluates the process-dependent weldability [...] Read more.

Cold-roll-bonded (CRB) Fe–Al clad sheets, which incorporate an internal steel layer within the clad structure, are candidate materials for dissimilar joining in lightweight structural applications, yet systematic comparisons of their weldability across multiple joining processes remain limited. This study evaluates the process-dependent weldability of CRB Fe–Al clad sheets using three joining processes: laser lap welding, DC resistance spot welding, and cold metal transfer-pulse (CMT-P) arc welding. Weld appearance, cross-sectional morphology, tensile shear behavior, and fracture characteristics were assessed for multiple sheet configurations and clad-layer thicknesses. Across all three processes, configurations that placed the clad sheet directly toward the heat source were prone to cracking or strength degradation when the internal steel layer melted extensively, whereas limiting steel-layer involvement produced more stable joints. Among the three processes, resistance spot welding provided the widest workable process window, while laser and CMT-P arc welding achieved peak strengths only within a narrow heat-input range. These findings indicate that the role of the internal steel layer is process-dependent and provide practical guidance for sheet configuration and parameter selection when joining CRB Fe–Al clad sheets to steel or aluminum components. Full article

(This article belongs to the Section Welding and Joining)

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16 pages, 1607 KB

Open AccessArticle

Investigation of Hydrophobicity Enhancement of Molybdenum Surfaces by Micromilling

by Xian Meng, Hao Xu, Hui Zhang, Jinwen Cao, Ying Zhang, Jinyue Geng, Cong Yan and Heji Huang

Metals 2026, 16(9), 991; https://doi.org/10.3390/met16090991 - 4 Sep 2026

Abstract

Molybdenum (Mo), owing to its excellent high-temperature resistance and low sputtering yield, is widely used in advanced equipment such as extreme ultraviolet (EUV) lithography systems. To meet the demand for regulating the surface wettability of Mo, this study employs micromilling to fabricate microgroove [...] Read more.

Molybdenum (Mo), owing to its excellent high-temperature resistance and low sputtering yield, is widely used in advanced equipment such as extreme ultraviolet (EUV) lithography systems. To meet the demand for regulating the surface wettability of Mo, this study employs micromilling to fabricate microgroove arrays on Mo surfaces to enhance their hydrophobicity. First, comparative micromilling experiments are conducted under flood cooling and minimum quantity cooling lubrication (MQCL) conditions. The effects of process parameters, including axial depth of cut (a_p), spindle speed (n), and feed per tooth (f_z), on burr height (H) are investigated under the two cooling/lubrication conditions. The results show that the burr heights obtained under flood cooling are generally lower than those obtained under MQCL. Subsequently, the machining parameters under flood cooling are evaluated using an orthogonal experimental design. A mathematical model relating the microgroove array geometry to the contact angle is then established based on Gibbs free energy to guide the design of surface microgroove structures. Finally, microgroove arrays are fabricated on Mo surfaces using the preferred machining parameters. The results demonstrate that the microgroove arrays effectively enhance the water hydrophobicity of the Mo surface. The static water contact angle increases from 62.45 ± 0.25° for the untreated Mo surface to a maximum of 128.50 ± 0.12°, thereby achieving a transition from hydrophilic to hydrophobic behavior. Full article

16 pages, 8389 KB

Open AccessArticle

Dielectric Polarization Mode Evolution-Induced Band-Tunable Microwave Absorption of Hollow Ni/C Microtubes

by Yunfei Wu, Jianxiang Wang, Kaiwen Li, Jiaheng Wang, Nan Lyu, Zhiyong Bao, Wenjuan Chen, Yong Zhang and Yucheng Wu

Metals 2026, 16(9), 990; https://doi.org/10.3390/met16090990 - 4 Sep 2026

Abstract

1D hollow Ni/C microtubes with tunable carbon shell coating were fabricated through a three-step method with carbon fiber templating, polydopamine coating and carbothermal reduction. The competitive behavior between NiO reduction and Ni-catalyzed graphitization dominates the evolution of carbon structure and interface state. Adjusting [...] Read more.

1D hollow Ni/C microtubes with tunable carbon shell coating were fabricated through a three-step method with carbon fiber templating, polydopamine coating and carbothermal reduction. The competitive behavior between NiO reduction and Ni-catalyzed graphitization dominates the evolution of carbon structure and interface state. Adjusting dopamine content achieves the dielectric polarization mode evolution from NiO/Ni Schottky junction to Ni/C interfacial and intrinsic dipole polarization, realizing band-tunable microwave absorption. With favorable modulation of the carbon shell, the absorber thickness required for efficient absorption declines substantially, while the absorbing bands shift from the X-Ku boundary toward high-frequency Ku and low-frequency S-C band. NC-3 with the thickest carbon coating delivers the strongest absorption of −49.58 dB at merely 1 mm, and its absorbing band can also be tuned to the S band at 6.6 mm. This work offers a concise interfacial strategy for lightweight and band-tunable microwave absorbers. Full article

28 pages, 3231 KB

Open AccessArticle

Evolution of Microstructure, Mechanical Properties and Crystallographic Orientation for T2 Copper Sheet Processed by Large Deformation Amount Followed by Different Annealing Treatment Processes

by Jinhua Zhao, Ziyang Li, Yali Hou, Zongyan Zou, Wenli Hu, Fei Ji and Wenwu He

Metals 2026, 16(9), 989; https://doi.org/10.3390/met16090989 - 4 Sep 2026

Abstract

Industrial pure copper sheets as a crucial electronic material have currently attracted extensive attention from scholars due to the rapid development of the information technology industry. However, past investigations into the regulation discipline of the microstructure and mechanical properties of pure copper have [...] Read more.

Industrial pure copper sheets as a crucial electronic material have currently attracted extensive attention from scholars due to the rapid development of the information technology industry. However, past investigations into the regulation discipline of the microstructure and mechanical properties of pure copper have not paid sufficient attention due to the inevitably low strength induced by the lack of alloying elements. In this study, a typical T2 copper sheet was fabricated by a severe cold-rolling process with a deformation amount of 83% followed by different annealing temperatures ranging from 200 to 500 °C, and the influence of annealing temperature on the evolution of microstructure, mechanical and physical properties and crystallographic orientation (CRO) was investigated systematically. The microstructure features and micro-texture of the studied T2 copper sheet were characterized by optical microscopy (OM) and scanning electron microscopy equipped with electron back-scattered diffraction (EBSD) techniques throughout the entire process from the initial state to the deformed state and annealed state, and the tensile property and electrical conductivity were tested by utilizing a universal testing machine and a digital micro-ohmmeter. Results indicate that the yield strength and tensile strength of the studied T2 copper sheet are both decreased with increasing annealing temperature, accompanied by an increase in electrical conductivity, and the maximum conductivity of up to 98.2% IACS can be reached at the annealing temperature of 500 °C. With the increase in annealing temperature, the degree of recrystallization becomes increasingly sufficient, and the volume fraction of recrystallized grains is increased from ~17.8% to ~35.7% with the annealing temperature increased from 200 to 500 °C. The texture component of the studied T2 copper sheet processed by severe cold rolling with a deformation amount of 83% is characterized by a deformation texture composed of copper texture and S texture, and is then transformed into a texture that predominantly consists of Cube texture under the application of annealing treatment, and the maximum intensity value of Cube texture is enhanced with the increase in annealing temperature. Full article

(This article belongs to the Special Issue Metal Forming and Additive Manufacturing)

17 pages, 3146 KB

Open AccessArticle

Feature Engineering-Driven Interpretable Machine Learning Study on the Corrosion Resistance of Zn-Al-Mg Coatings

by Haochang Tang, Muhua Chang and Lin Lu

Metals 2026, 16(9), 988; https://doi.org/10.3390/met16090988 - 4 Sep 2026

Abstract

Zn-Al-Mg (ZAM) coatings have attracted significant attention in the field of corrosion protection owing to their combination of excellent corrosion resistance and cost-effectiveness. However, the corrosion behavior of ZAM coatings was governed by the synergistic coupling effects of multiple factors, including alloy composition, [...] Read more.

Zn-Al-Mg (ZAM) coatings have attracted significant attention in the field of corrosion protection owing to their combination of excellent corrosion resistance and cost-effectiveness. However, the corrosion behavior of ZAM coatings was governed by the synergistic coupling effects of multiple factors, including alloy composition, coating thickness, corrosive medium, and multiphase microstructure, making it challenging for traditional empirical analysis to systematically reveal the underlying mechanisms. To address this challenge, we constructed a multidimensional corrosion dataset comprising alloy composition, corrosive medium, coating thickness, and phase composition, based on literature data from the past three decades combined with self-measured potentiodynamic polarization experimental results. After data normalization and correlation analysis, we introduced phase structure features—including the Al-rich phase, MgZn₂ phase, Mg₂Si phase, and eutectic microstructures—to enhance the model’s capability in representing microstructural factors. On this basis, we established random forest (RF), support vector regression (SVR), and artificial neural network (ANN) models to predict the corrosion current density, and subsequently conducted an interpretability analysis using the SHapley Additive exPlanations (SHAP) method. The results demonstrated that the expanded feature set significantly improved the prediction performance of the models. Among them, the RF model exhibited the best performance, achieving a determination coefficient (R²) of 0.7363 on the test set, which represented a substantial improvement over the baseline dataset. Feature importance analysis revealed that coating thickness, Mg content, NaCl concentration, and Zn content were the primary factors influencing the corrosion current density. Further SHAP analysis showed that the marginal contribution of the eutectic phase was more prominent in local samples. Meanwhile, the Mg element exhibited distinct non-linear regulation characteristics, exerting varying impacts on the corrosion behavior across different concentration ranges. This study demonstrated that the interpretable machine learning models constructed via feature engineering not only improved the prediction accuracy of the corrosion performance of ZAM coatings, but also provided a novel data-driven approach to revealing the intrinsic correlations among alloy composition, phase structure, and corrosion response. Full article

11 pages, 602 KB

Open AccessArticle

Optimization of Chromium Production Waste Treatment Processes

by Alexander Kim, Alexander Akberdin, Ruslan Sultangaziyev and Kalamkas Titosheva

Metals 2026, 16(9), 987; https://doi.org/10.3390/met16090987 - 4 Sep 2026

Abstract

This paper presents the results of a study on the utilization of chromium-containing waste in the production of mineral wool based on natural basalt. It was shown that a mixture of low-dolomite chromate sludge and low-carbon ferrochrome slag in a 1:1 ratio is [...] Read more.

This paper presents the results of a study on the utilization of chromium-containing waste in the production of mineral wool based on natural basalt. It was shown that a mixture of low-dolomite chromate sludge and low-carbon ferrochrome slag in a 1:1 ratio is compositionally close to dolomite. When dolomite is equivalently replaced in the mineral wool batch, the physicochemical characteristics of the melt remain suitable for mineral wool production. The complete reduction of iron and chromium oxides is achieved in the presence of carbon, resulting in their transfer to the metallic phase, where iron and chromium cations are present in the form of carbides. Due to the cost difference between chromium waste and dolomite, implementing the proposed technology makes it possible to significantly improve the efficiency of chromium waste utilization by reducing the production cost of mineral wool. The Aktobe region has all the prerequisites for implementing the developed technology, with active sources of chromium-containing waste pollution (ACCP, AFP) and basalt deposits, as well as the operational experience of the mineral-wool-manufacturing enterprise Basalt-A LLP. Full article

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15 pages, 3341 KB

Open AccessArticle

Kinetics of Secondary Recrystallization in Grain-Oriented Silicon Steel Based on Grain Size Distribution

by Fang Zhang, Yan Xie, Zhanyi Xu, Hanzheng Zhang and Yuhui Sha

Metals 2026, 16(9), 986; https://doi.org/10.3390/met16090986 - 4 Sep 2026

Abstract

Quasi in situ observations of the early stage of secondary recrystallization in Fe-3.25 wt.% Si high-permeability grain-oriented silicon steel indicate that large matrix grains locally impede the migration of secondary recrystallized grain boundaries. A critical grain-size criterion for identifying potential pinning grains is [...] Read more.

Quasi in situ observations of the early stage of secondary recrystallization in Fe-3.25 wt.% Si high-permeability grain-oriented silicon steel indicate that large matrix grains locally impede the migration of secondary recrystallized grain boundaries. A critical grain-size criterion for identifying potential pinning grains is proposed, and a kinetic model incorporating the matrix grain-size distribution is developed. For the abnormal grain tracked at 1000 °C, the measured grain-size increment over 100 s was approximately 60 μm; the proposed pinning model predicted 47 μm, whereas the weighted-average model predicted 171 μm. Model calculations further suggest that matrix grain-size dispersion, pinning force, grain size, and relative grain-boundary energy jointly affect the early-stage growth of Goss grains. These results provide a framework for interpreting early secondary-recrystallization kinetics, while broader experimental validation is still required before the predicted parameter combinations can be used for process control. Full article

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

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24 pages, 27000 KB

Open AccessArticle

Effect of Ceramic Reinforcement Type on Friction Stability and Wear Resistance of Cu and Cu–Bronze Matrix Powder Metallurgy Brake Composites

by Gürkan Soy, Hasan Öktem, Sıtkı Akıncıoğlu and İlyas Uygur

Metals 2026, 16(9), 985; https://doi.org/10.3390/met16090985 - 4 Sep 2026

Abstract

The tribological performance of copper-matrix sintered brake pads for high-speed rail applications is strongly influenced by ceramic reinforcement type. However, a systematic comparison of SiC, ZrO₂, and SiO₂ within Cu and Cu–Bronze (Cu–Br) matrix systems remains limited. In this study, [...] Read more.

The tribological performance of copper-matrix sintered brake pads for high-speed rail applications is strongly influenced by ceramic reinforcement type. However, a systematic comparison of SiC, ZrO₂, and SiO₂ within Cu and Cu–Bronze (Cu–Br) matrix systems remains limited. In this study, six powder metallurgy composites were produced by cold pressing and sintering at 900 °C, with each matrix reinforced with 2 wt.% SiC, ZrO₂, or SiO₂ and containing graphite and MoS₂ as solid lubricants. Tribological tests were performed at 25, 100, and 400 °C under an 18 N normal load. Microstructural and thermal characteristics were evaluated using optical microscopy, SEM/EDS, and DTA/TGA. The coefficient of friction (COF) ranged from 0.163 to 0.364 across all formulations and temperatures. The Cu–Br-based composites exhibited a narrower reinforcement-dependent COF range than the Cu-based composites, particularly at elevated temperatures. Cu–SiO₂ showed the highest COF within the Cu-based at all test temperatures, whereas Cu–Br–SiC composite exhibited the highest COF among the Cu–Br-based composites at 400 °C. The lowest specific wear rates were obtained for Cu–SiO₂ at 25 °C and Cu–SiC at 400 °C. SiC-reinforced composites exhibited the highest hardness within both matrix systems. Full article

(This article belongs to the Section Metal Matrix Composites)

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17 pages, 2577 KB

Open AccessArticle

Characterising Ionised Air Metalworking Fluid Application During Titanium Alloy Shoulder Milling

by Leon Proud, Ian Cook, Pete Crawforth and Chris M. Taylor

Metals 2026, 16(9), 984; https://doi.org/10.3390/met16090984 - 4 Sep 2026

Abstract

As manufacturers seek to improve cutting process sustainability, alternative metalworking fluid (MWF) strategies are increasingly being explored. For the first time, this study characterises tool wear when shoulder milling both Grade 5 titanium (Ti-6Al-4V) and Grade 2 commercially pure titanium (CP-Ti) with a [...] Read more.

As manufacturers seek to improve cutting process sustainability, alternative metalworking fluid (MWF) strategies are increasingly being explored. For the first time, this study characterises tool wear when shoulder milling both Grade 5 titanium (Ti-6Al-4V) and Grade 2 commercially pure titanium (CP-Ti) with a novel through-spindle Aurion Machining Technologies ionised air (IA) MWF setup. Preliminary results show that during CP-Ti milling trials, the IA strategy led to a tool life of between 85% and 91% of that which was achieved with soluble oil emulsion MWF, whilst during Ti-6Al-4V milling the observed tool life with IA was between 158% and 278% greater than with emulsion coolant at analogous cutting conditions (2.58 and 3.78 times respectively). In addition, IA generated a 26.2% reduction in surface roughness after Ti-6Al-4V milling, potentially indicating a change in tool–surface interaction behaviour. These benefits are compounded as IA returns to its original condition rapidly after utilisation, meaning low environmental and health impact with no waste MWF liquids/gases/mist, clean metal cuttings and low delivery power. Beyond these promising results, cooled and dried but non-ionised air was also shown to perform strongly (regarding tool wear in Ti-6Al-4V milling), relative to emulsion MWF, such that at 190 m/min cutting speed it generated 90% of the tool life which was achieved by the IA strategy. Whilst these preliminary findings require confirmation through repeat testing, IA remains of clear interest for further experimental investigation across a range of subtractive processes. Moreover, this work highlights the potential benefits, niches and configurations for air-based MWFs in general, with further mechanistic and tribological exploration warranted. Full article

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28 pages, 3287 KB

Open AccessReview

Additive Manufacturing of Particle-Reinforced Aluminum Matrix Composites for Aerospace Applications

by Shuai Zhang, Bingbing Li, Zhaofeng Wang, Jiawei Han and Qiang Shi

Metals 2026, 16(9), 983; https://doi.org/10.3390/met16090983 - 4 Sep 2026

Abstract

Additive manufacturing offers a novel technical route for the fabrication of complex lightweight aluminum alloy components in the aerospace field. However, high-strength aluminum alloys still suffer from defects such as hot cracking, porosity and microstructural inhomogeneity during the forming process. Particle reinforcement is [...] Read more.

Additive manufacturing offers a novel technical route for the fabrication of complex lightweight aluminum alloy components in the aerospace field. However, high-strength aluminum alloys still suffer from defects such as hot cracking, porosity and microstructural inhomogeneity during the forming process. Particle reinforcement is a critical strategy to enhance the properties of additively manufactured aluminum matrix composites. Focusing on three mainstream processes, namely powder bed fusion–laser beam (PBF-LB), directed energy deposition–arc (DED-Arc) and directed energy deposition–laser beam (DED-LB), this paper elaborates on the roles of typical reinforcement particles including TiB₂, TiC, SiC and CaB₆ in microstructure tailoring, defect suppression and property enhancement. It further compares the three processes in terms of forming characteristics, microstructure evolution and aerospace applications. Finally, key challenges including particle dispersion, interfacial stability, process consistency and engineering application are summarized, and corresponding future development prospects are discussed. Full article

(This article belongs to the Section Metal Matrix Composites)

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22 pages, 9310 KB

Open AccessArticle

Numerical Modeling of Microstructure Evolution in Nanocrystalline Alloys—Grain Boundary Segregation, Solute Drag, and Mechanics

by Prakarsh Pandey and Shiva Rudraraju

Metals 2026, 16(9), 982; https://doi.org/10.3390/met16090982 - 4 Sep 2026

Abstract

Nanocrystalline (NC) alloys hold significant promise as structural alloys due to their superior mechanical properties over the traditional coarser grained microcrystalline alloys. Often, there is an optimal range of mean grain size for most metals about which maximum material strength can be realized. [...] Read more.

Nanocrystalline (NC) alloys hold significant promise as structural alloys due to their superior mechanical properties over the traditional coarser grained microcrystalline alloys. Often, there is an optimal range of mean grain size for most metals about which maximum material strength can be realized. In the context of NC alloys, stabilization of the grain size in this optimal range is one of the primary synthesis challenges. A large volume fraction of NC alloy microstructure is occupied by grain boundaries (GBs). Since GBs increase the internal surface energy of the system, during solidification and grain growth phases, there is a tendency to minimize GBs through grain coarsening. However, in NC alloys, phenomena like GB–solute segregation and solute precipitation are active and mitigate grain growth and thus stabilize the desired small grains. Numerically modeling these phenomena of GB–solute interactions, and the evolution of these stabilized GBs under mechanical load, is of immense interest to the NC alloy community. To enrich the numerical modeling formulations available in this space, we present here a phase-field-method-based numerical framework to model GB segregation, solute precipitation and effect of external loading on NC alloys. While some of these effects have been modeled in isolation, a unified treatment of the solute–GB segregation-related effects and its coupling with mechanics has not be considered in the literature. We present a three-dimensional, finite element method (FEM)-based, finite-strain phase-field formulation for modeling grain evolution and microstructure stabilization in NC alloys. Beyond the formulation and its computational implementation, various case studies demonstrate the applicability of this framework. Further, thermodynamic and kinetic arguments are provided based on the evolution of GB energy to explain the effects of solute drag, GB pinning and mechanical deformation. Full article

(This article belongs to the Special Issue Deformation of Metals and Alloys: Theory, Simulations and Experiments—2nd Edition)

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20 pages, 21385 KB

Open AccessArticle

Effect of Strip Width on Strip Shape in Ultra-Wide-Strip Tandem Cold Mill

by Lianjie Li, Hongqiang Liu, Xindong Wang, Haibo Xie, Hongwei Cao, Teng Li, Xu Liu, Tianwu Liu, Kai Chen, Chuanbao Zheng, Haobin Tian, Li Sun and Zhengyi Jiang

Metals 2026, 16(9), 981; https://doi.org/10.3390/met16090981 - 3 Sep 2026

Abstract

The strip width in ultra-wide-strip tandem cold rolling changes not only the total rolling load, but also the transverse span over which the work roll (WR) is loaded. This study quantifies the isolated width effect on strip crown at 40 mm from the [...] Read more.

The strip width in ultra-wide-strip tandem cold rolling changes not only the total rolling load, but also the transverse span over which the work roll (WR) is loaded. This study quantifies the isolated width effect on strip crown at 40 mm from the edge (

C_{40}

), flatness and WR elastic deformation in a 2180 mm CVC-6 tandem cold mill. A three-dimensional multi-stand elastic–plastic finite element (EPFE) model was established for five representative widths of 900, 1200, 1500, 1800 and 2100 mm, corresponding to contact-span ratios of 0.413–0.963. The results show that the strip width increased from 900 mm to 2100 mm,

C_{40}

decreased from 20~80 μm to −50~−280 μm, and 1800 mm was the transition point from the positive crown to the negative crown. At the same time, the quadratic flatness component increased toward a center-wave mode, whereas the quartic component decreased toward an edge–center coupled-wave mode. Mechanistically, the relative WR axis deflection at the strip edge increased much faster than the local WR flattening compensation, producing an edge-open loaded roll gap. The findings indicate that strip width should be treated as an independent preset variable for WR bending, intermediate-roll bending and intermediate-roll shifting in ultra-wide cold rolling. Full article

(This article belongs to the Special Issue Advances in the Forming of Metals and Their Alloys)

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21 pages, 2048 KB

Open AccessArticle

Optimization of the Pulsed Laser Cladding Process to Improve the Wear Resistance of (Ti, V)C/Ni Coatings

by Bohan Zhang, Ze Sun, Wei Liu, Kaiming Wang, Yulong Zheng and Hanguang Fu

Metals 2026, 16(9), 980; https://doi.org/10.3390/met16090980 - 3 Sep 2026

Abstract

Continuous laser cladding of Ni-based composite coatings commonly suffers from coarse microstructures, high residual stress, severe cracking susceptibility, and limited wear performance. Although substrate preheating is an effective strategy for crack suppression, it inevitably induces microstructural coarsening and deteriorates mechanical and tribological properties, [...] Read more.

Continuous laser cladding of Ni-based composite coatings commonly suffers from coarse microstructures, high residual stress, severe cracking susceptibility, and limited wear performance. Although substrate preheating is an effective strategy for crack suppression, it inevitably induces microstructural coarsening and deteriorates mechanical and tribological properties, while the independent and coupled effects of pulsed laser modulation and preheating on (Ti, V)C/Ni coating performance remain insufficiently quantified and clarified. To address these technical gaps, this work fabricates (Ti, V)C/Ni composite coatings on Cr12MoV die steel via pulsed laser cladding. An L₁₆ orthogonal experiment is employed to systematically investigate the influences of average power, duty cycle, and pulse frequency on coating hardness, and the optimal pulsed laser parameters are determined as 1750 W average power, 65% duty cycle, and 10 Hz pulse frequency. Under optimized parameters, the pulsed-laser-clad coating achieves a maximum hardness of 898.6 HV_0.2, exhibiting 10.2% higher hardness and 41.4% better wear resistance than its continuous laser-clad counterpart, owing to the refined microstructure and enhanced grain-strengthening effect induced by rapid pulsed thermal cycling. Further comparative experiments demonstrate that substrate preheating combined with pulsed laser cladding effectively eliminates coating cracks and reduces residual stress by alleviating concentrated thermal strain. Nevertheless, preheating-induced microstructure coarsening slightly reduces the hardness and wear resistance of the composite coating compared with the purely pulsed laser-processed coating. In summary, pure pulsed laser processing dominates the improvement in wear resistance, whereas preheating mainly contributes to defect suppression and stress relief, enabling reliable engineering application of laser-clad coatings. Full article

(This article belongs to the Special Issue Machining, Grinding, and Laser Processing of Metallic Materials)

36 pages, 2817 KB

Open AccessReview

Plant-Based Corrosion Inhibitors for Reinforced Concrete Under Chloride Attack: Advances, Mechanisms, and Prospects

by Mingyuan Xiong, Changshi Huang, Guowei Wang, Xiaocheng Zhou and Dan Song

Metals 2026, 16(9), 979; https://doi.org/10.3390/met16090979 - 3 Sep 2026

Abstract

Chloride-induced steel corrosion is one of the major causes of durability degradation in reinforced concrete (RC) structures. Conventional inhibitors have inherent drawbacks in environmental safety, long-term stability, and cement compatibility. Plant extracts, featuring renewability, biodegradability, and abundant bioactive components, have emerged as promising [...] Read more.

Chloride-induced steel corrosion is one of the major causes of durability degradation in reinforced concrete (RC) structures. Conventional inhibitors have inherent drawbacks in environmental safety, long-term stability, and cement compatibility. Plant extracts, featuring renewability, biodegradability, and abundant bioactive components, have emerged as promising green corrosion inhibitors. This review summarizes the categories, inhibition mechanisms, and evaluation methods of plant-based inhibitors, and discusses multi-scale characterization and computational techniques for mechanism research. A conceptual Ginkgo biloba extract (EGb)-LDH strategy is discussed as a possible future route for plant-based inhibitor delivery, but its chloride-responsive release and corrosion-protection performance remain to be experimentally verified. Full article

(This article belongs to the Special Issue Corrosion Mechanisms and Cutting-Edge Protection Technologies for Advanced Alloy Materials)

18 pages, 1110 KB

Open AccessArticle

Synthesis of Micron-Sized Spherical Gold Powders for Gold Conductor Pastes: Effects of Powder Characteristics on Sintering Behavior and Thick-Film Performance

by Xinyu Zhou, Zhiqiang Xia, Qiang Wen, Zhen Pang, Baisen Hou, Yunxia Shi, Hu Sun, Junpeng Li, Zhuo Qian, Xianglei Yu and Guoyou Gan

Metals 2026, 16(9), 978; https://doi.org/10.3390/met16090978 - 3 Sep 2026

Abstract

Micron-sized spherical gold powders possessing high dispersibility and favorable sintering performance are critical for high-performance thick-film gold conductor pastes. Herein, monodisperse micron-sized spherical gold powders were fabricated through an environmentally benign chemical reduction route, where L-ascorbic acid served as the reductant and gum [...] Read more.

Micron-sized spherical gold powders possessing high dispersibility and favorable sintering performance are critical for high-performance thick-film gold conductor pastes. Herein, monodisperse micron-sized spherical gold powders were fabricated through an environmentally benign chemical reduction route, where L-ascorbic acid served as the reductant and gum arabic acted as the dispersant. The influences of solution pH, reaction temperature, stirring speed and reaction time on particle morphology and size distribution were systematically explored. With the mass ratio of gold precursor to reductant maintained at 1:1, the optimal synthetic conditions were determined as pH 3, 20 °C, 550 rpm and 20 min. Under such optimized conditions, spherical gold particles with an average diameter of 0.88 μm were harvested, featuring narrow particle-size distribution, high sphericity, good dispersibility and low organic residue of 0.70 wt%. The as-prepared powder delivered high crystallinity and appropriate sintering activity. Quantitative porosity characterization demonstrated that the thick film derived from this micron-scale gold powder achieved the minimum residual porosity in comparison with the other two counterparts, verifying its outstanding densification behavior. Benefiting from the well-developed dense conductive network, the resultant thick film achieved a low sheet resistance of 1.73 mΩ/sq, a superior adhesion strength of 3.65 N/mm², as well as reliable multi-firing stability. This work offers a feasible approach for large-scale manufacturing of high-quality gold powders toward thick-film electronic devices. Full article

(This article belongs to the Section Metallic Functional Materials)

21 pages, 23988 KB

Open AccessArticle

Atmosphere-Controlled Solid-State Decarburization and Evolution of Carbon-Gradient Microstructures in Medium-Mn Steel

by Xinchan Nie, Caijiao Sun, Lukuo Hong, Shuai Tong and Meijie Zhou

Metals 2026, 16(9), 977; https://doi.org/10.3390/met16090977 - 3 Sep 2026

Abstract

Controlling carbon removal while limiting surface oxidation is essential for constructing composition gradients in high-carbon medium-Mn steel. In this study, solid-state decarburization of Fe-12 wt%Mn-2.7 wt%C alloy sheets was investigated in H₂O-H₂ and CO₂-CO atmospheres by combining thermodynamic [...] Read more.

Controlling carbon removal while limiting surface oxidation is essential for constructing composition gradients in high-carbon medium-Mn steel. In this study, solid-state decarburization of Fe-12 wt%Mn-2.7 wt%C alloy sheets was investigated in H₂O-H₂ and CO₂-CO atmospheres by combining thermodynamic calculations with XRD, SEM, OM, EBSD, and GDOES characterization. Thermodynamic analysis showed that, above 1190 K, the critical gas partial-pressure ratio for Fe oxidation is lower in CO₂-CO than in H₂O-H₂, while the competitive-oxidation analysis further indicated a wider selective-oxidation window in the H₂O-H₂ atmosphere. Experimentally, H₂O-H₂ produced a relatively uniform oxide layer with a clear interface, whereas P_CO₂/P_CO ≥ 0.29 promoted finger-like MnO growth along grain boundaries in CO₂-CO. In both atmospheres, increasing temperature accelerated carbon removal. At 1363 K and 50 min, increasing P_H₂O/P_H₂ from 0.47 to 0.51 and further to 0.56 progressively reduced the carbon concentration at a depth of approximately 450 μm from approximately 0.50 to 0.45 and finally to 0.30 at%, demonstrating effective regulation of the through-thickness carbon gradient. EBSD of the specimen treated at 1323 K for 50 min with P_H₂O/P_H₂ = 0.47 revealed a near-surface α + γ microstructure and a γ-dominated near-center region, with the number-weighted mean grain size increasing from approximately 14.5 to 59.5 μm. These results establish a processing-microstructure relationship among atmosphere-dependent selective oxidation, carbon removal, and carbon-gradient microstructure formation in medium-Mn steel. Full article

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

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22 pages, 18632 KB

Open AccessArticle

Microstructure Evolution of Cu-Ag Alloy During Directional Solidification Under a Transverse Magnetic Field

by Quan Xiao, Haoran Zhang, Xianglei Dong, Hui Xing, Shuya Zhang, Yuheng Fan, Junhua Hu and Hongliang Zhao

Metals 2026, 16(9), 976; https://doi.org/10.3390/met16090976 - 3 Sep 2026

Abstract

Magnetic field-assisted casting technologies have received extensive research attention. Applying a transverse magnetic field during directional solidification offers an effective, non-contact approach to control the microstructure of Cu-Ag alloys by modulating melt convection. However, a comprehensive quantitative understanding of its mesoscopic influence on [...] Read more.

Magnetic field-assisted casting technologies have received extensive research attention. Applying a transverse magnetic field during directional solidification offers an effective, non-contact approach to control the microstructure of Cu-Ag alloys by modulating melt convection. However, a comprehensive quantitative understanding of its mesoscopic influence on solute-driven dendritic growth and the columnar-to-equiaxed transition (CET) is still lacking. In this study, a coupled phase-field and lattice Boltzmann (PF-LBM) model is employed to systematically investigate the effect of a transverse magnetic field on columnar dendrite evolution and CET kinetics during the directional solidification of Cu-Ag alloys. Results show that the field-induced Lorentz force disrupts the symmetry of the solute field ahead of the dendrite tip, driving tilted dendritic growth that intensifies with decreasing initial primary spacing. During the CET process, the magnetic field overrides the randomness of grain nucleation by selecting specific crystallographic orientations. More importantly, it effectively mitigates the thermodynamic suppression of equiaxed nucleation typically caused by high temperature gradients. Furthermore, an increased magnetic field intensity not only accelerates the occurrence of CET but also significantly diminishes the inhibitory effect of high nucleation barriers on the transition. Ultimately, this work provides fundamental insights into external field-induced orientation selection mechanisms of as-cast grains and establishes a theoretical framework for quantitatively controlling texture evolution during the subsequent processing of high-flexure Cu-Ag alloys. Full article

(This article belongs to the Special Issue Modeling and Simulation of Microstructural Evolution in Metallic Materials)

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17 pages, 6332 KB

Open AccessArticle

Influence of Vibration Assistance on Slurry Rheological Behavior and Polishing Performance in Force Rheological Polishing

by Qi Shao, Binghai Lyu, Luguang Guo, Jiahuan Wang, Xiaofeng Lin, Dabin Zhang, Ping Zhao and Julong Yuan

Metals 2026, 16(9), 975; https://doi.org/10.3390/met16090975 - 3 Sep 2026

Abstract

The increasing demand for ultra-precision components with complex surface geometries has stimulated the development of advanced deterministic polishing technologies. This investigation explores the impact of external vibration on the rheological properties of polishing slurry and the material removal performance during the vibration-assisted force [...] Read more.

The increasing demand for ultra-precision components with complex surface geometries has stimulated the development of advanced deterministic polishing technologies. This investigation explores the impact of external vibration on the rheological properties of polishing slurry and the material removal performance during the vibration-assisted force rheological polishing (VFRP) process. The mechanical response of the vibrating workpiece surface under various vibration conditions was numerically analyzed using ANSYS Fluent 14.5. The results demonstrated a strong correlation between the surface pressure imposed on the workpiece and the applied vibration amplitude as well as vibration frequency. Experimental results validate that the introduction of vibration promotes a reversible rheological transition of the slurry from a fluid-predominant state to a solid-resembling structure, which facilitates abrasive particle confinement and subsequently enhances polishing capability. The reliance of stainless-steel sheet polishing performance on vibration parameters was evaluated. With the optimized combination of polishing speed (40 rpm), vibration frequency (80 Hz), and amplitude (0.35 mm), the 30 min polishing process yielded a material removal rate of 68.1 nm/min and reduced the average surface roughness (S_a) from 80 nm to 7.1 nm. The acquired results provide constructive direction for optimizing the VFRP process and promoting its application in high-efficiency, ultra-precision surface polishing. Full article

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