Metals

16 pages, 15593 KB

Open AccessArticle

Atmospheric Corrosion of High-Lead Bronze: From Cerussite Patina to Bronze Disease

by Zengwei Ji, Lang Guo, Liqin Wang, Yanni Ma, Ren Li, Zeduan Pan and Xing Zhao

Metals 2026, 16(8), 938; https://doi.org/10.3390/met16080938 - 21 Aug 2026

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This study investigates the atmospheric corrosion behavior of high-lead bronze alloys within a simulated aggressive environment characterized by high humidity, acidity, chlorides, oxygen, and CO₂. The evolution of surface morphology and corrosion products was systematically monitored using colorimetric analysis and micro-Raman [...] Read more.

This study investigates the atmospheric corrosion behavior of high-lead bronze alloys within a simulated aggressive environment characterized by high humidity, acidity, chlorides, oxygen, and CO₂. The evolution of surface morphology and corrosion products was systematically monitored using colorimetric analysis and micro-Raman spectroscopy. Results indicate that the initial patina primarily comprised cuprite (Cu₂O) and cassiterite (SnO₂), which are predominantly benign phases. During the early corrosion stage, lead oxidation and carbonation prevailed, generating abundant bright-white cerussite. Subsequently, as copper-driven corrosion became dominant, these white deposits diminished and were progressively replaced by characteristic green “bronze disease”, identified as atacamite (Cu₂(OH)₃Cl). The findings reveal that preferential lead corrosion is likely to induce localized pitting, thereby accelerating degradation of the copper substrate. Consequently, higher lead content may reduce the overall corrosion resistance of bronze artifacts under these specific conditions. These results offer experimental insights into atmospheric corrosion mechanisms and inform the development of evidence-based conservation strategies for bronze cultural heritage. Full article

(This article belongs to the Section Corrosion and Protection)

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17 pages, 10358 KB

Open AccessArticle

Recovery of Germanium from Zinc Smelting Leachate Using a Novel Hydroxamic Acid Extractant BGYW: Continuous Counter-Current Extraction and Process Optimization

by Zong Guo, Zhenyu Wang, Zhixing Qin, Tao Li, Haibei Wang, Yunchuan Ma, Yun Li, Guang Fu, Hao Ma and Chaozhen Zheng

Metals 2026, 16(8), 937; https://doi.org/10.3390/met16080937 - 21 Aug 2026

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Abstract

Germanium is a critical rare-dispersed metal with irreplaceable applications in infrared optics, fiber-optic communications, and semiconductor industries, making its efficient recovery from secondary resources of great strategic importance. This study investigates the selective recovery of germanium from complex zinc smelting leachates using a [...] Read more.

Germanium is a critical rare-dispersed metal with irreplaceable applications in infrared optics, fiber-optic communications, and semiconductor industries, making its efficient recovery from secondary resources of great strategic importance. This study investigates the selective recovery of germanium from complex zinc smelting leachates using a novel hydroxamic acid extractant, BGYW, in synergistic combination with P204. The feed solution contained approximately 360 mg/L Ge, 10,790 mg/L Fe²⁺, and 98,530 mg/L Zn, representing a highly complex matrix. Continuous counter-current extraction was performed in a 30-stage miniature mixer-settler. Under optimized conditions of 10% BGYW + 5% P204 in white oil, an O/A ratio of 1:1, and 8 mol/L NH₄F as strippant, the single-stage germanium extraction efficiency reached 99.4%. Over 16 consecutive cycles, the extraction system maintained stable performance with average germanium extraction above 99%. A 3-stage scrubbing section using 50 g/L H₂SO₄ effectively removed co-extracted Zn, Cu, and Al impurities. Iron co-extraction, a major challenge, was successfully mitigated through a 2–3 stage iron scrubbing step using a chloride-containing scrubbing solution, which reduced the iron concentration in the strip liquor from approximately 600 mg/L to below 4 mg/L, and decreased the Fe/Ge mass ratio from 0.197 to below 0.01. The overall germanium recovery across the entire 30-stage continuous process reached 98.82%, and the dissolution loss of BGYW in the aqueous phase was reduced by over 85% compared to the conventional YW100 extractant. Third-phase formation caused by residual organic flocculants from the leaching step was eliminated through enhanced pre-treatment, while ferric fluoride precipitation in the stripping section was resolved by incorporating the iron scrubbing stage. This study demonstrates that the BGYW-P204 extraction system with the integrated iron scrubbing step offers an efficient, stable, and industrially viable approach for germanium recovery from zinc smelting leachates, providing a practical solution to the long-standing challenge of germanium–iron separation and contributing to the sustainable supply of this critical metal. Full article

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

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17 pages, 39515 KB

Open AccessArticle

EBSD-Derived Misorientation Analysis of Stage-Dependent Grain Refinement in High-Pressure-Torsion-Processed AA1050 Aluminium

by Hui Wang, Shuxin Bo, Chen Yuan, Shouwei Xu, Guanyu Deng, Yu Liu and Rui Wang

Metals 2026, 16(8), 936; https://doi.org/10.3390/met16080936 - 21 Aug 2026

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Abstract

The grain refinement of high-stacking-fault-energy metals during high-pressure torsion (HPT) is governed by dislocation activity and boundary evolution. However, how local misorientation evolves during different stages of grain refinement remains insufficiently clarified. In this study, AA1050 aluminium was processed by HPT to selected [...] Read more.

The grain refinement of high-stacking-fault-energy metals during high-pressure torsion (HPT) is governed by dislocation activity and boundary evolution. However, how local misorientation evolves during different stages of grain refinement remains insufficiently clarified. In this study, AA1050 aluminium was processed by HPT to selected equivalent strains of 0, 0.90, 2.69, 10.76 and 53.78, and electron backscatter diffraction (EBSD) was used to analyse grain morphology, boundary fractions and EBSD-derived misorientation parameters. The results reveal strongly stage-dependent grain refinement during HPT. The average grain size decreases rapidly from 12.63 μm in the initial state to 3.29 μm at ε = 0.90 and 2.19 μm at ε = 2.69, remains nearly unchanged at ε = 10.76, and finally decreases to 0.58 μm at ε = 53.78. The fraction of low-angle grain boundaries increases markedly at ε = 0.90, indicating intensive formation of dislocation substructures, whereas high-angle grain boundaries become dominant at high strain. Grain orientation spread (GOS) and grain reference orientation deviation (GROD) exhibit non-monotonic evolution, whereas the geometrically necessary dislocation (GND) density increases markedly at the early deformation stage and subsequently decreases with further deformation. These results indicate that the stage-dependent grain refinement of AA1050 during HPT is closely associated with dislocation-mediated grain subdivision involving alternating grain elongation and fragmentation. Full article

(This article belongs to the Special Issue Phase Stability and Microstructural Evolution in Aluminum Alloys)

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19 pages, 14539 KB

Open AccessArticle

Optimization Study on the Process Parameters for Molybdenum Milling

by Xian Meng, Hao Xu, Haochen Li, Jinwen Cao, Jinyue Geng, Cong Yan, Xiang Cheng and Heji Huang

Metals 2026, 16(8), 935; https://doi.org/10.3390/met16080935 - 21 Aug 2026

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Abstract

Molybdenum (Mo), owing to its excellent properties, is widely used as a plasma-facing material and is recognized as a typical difficult-to-machine material. Achieving high-quality, low-damage machining is essential for ensuring the service reliability of Mo components. However, studies on the milling of Mo [...] Read more.

Molybdenum (Mo), owing to its excellent properties, is widely used as a plasma-facing material and is recognized as a typical difficult-to-machine material. Achieving high-quality, low-damage machining is essential for ensuring the service reliability of Mo components. However, studies on the milling of Mo remain limited. Therefore, this study investigates a high-quality, low-damage milling technique for Mo based on analyses of milling force, machined surface roughness, and white layer formation. First, the effects of machining parameters, including radial depth of cut (a_e), spindle speed (n), and feed per tooth (f_z), on the responses, namely milling force (F) and surface roughness (R_a), were investigated. The relationships between milling force, surface roughness, and white layer formation were analyzed. Subsequently, the response surface methodology (RSM) was employed to reveal the influence mechanisms of the machining parameters and their interactions on the response variables. Finally, a Kriging surrogate model integrated with the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was adopted to identify the optimal machining parameter combination for high-quality, low-damage milling. The results indicate that the milling force and white-layer thickness exhibit consistent increasing trends with increasing feed per tooth under the investigated conditions, demonstrating that controlling the milling force is an effective approach for achieving high-quality, low-damage milling of Mo. For the simultaneous minimization of milling force and surface roughness, the optimal machining parameters were determined to be a radial depth of cut of 0.2101 mm, a spindle speed of 10,090.7 rpm, and a feed per tooth of 0.01 mm/z. These findings provide valuable process parameter guidance for the precision machining of Mo components. Full article

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19 pages, 18384 KB

Open AccessArticle

Hot Deformation Behavior and Microstructural Evolution of a High-Strength Mg-Gd-Y-Zr Alloy

by Haitao Xie, Zhiwei Liang, Di Mei, Aiyue Zhang, Chenchen Jiang, Qingshan Du, Yang Xiao, Shijie Zhu, Liguo Wang, Chujie Liu, Jinxue Liu and Shaokang Guan

Metals 2026, 16(8), 934; https://doi.org/10.3390/met16080934 - 21 Aug 2026

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Abstract

Mg-Gd-Y-Zr alloys, with strong age-hardening and thermal stability, are ideal for lightweight load-bearing components, yet forming large complex parts is limited by high sensitivity to hot deformation parameters. This work investigates the hot deformation behavior and microstructure evolution of a Mg-9Gd-4Y-0.5Zr (wt.%) alloy [...] Read more.

Mg-Gd-Y-Zr alloys, with strong age-hardening and thermal stability, are ideal for lightweight load-bearing components, yet forming large complex parts is limited by high sensitivity to hot deformation parameters. This work investigates the hot deformation behavior and microstructure evolution of a Mg-9Gd-4Y-0.5Zr (wt.%) alloy via hot compression at 400 to 510 °C and strain rates of 0.001 to 10 s⁻¹. An Arrhenius constitutive equation with an activation energy Q of 158.63 kJ/mol was established, and a hot processing map was constructed. EBSD characterization revealed the dynamic recrystallization, grain size evolution, and texture transition. The results show that flow stress depends strongly on temperature and strain rate. At strain rates of 0.001~1 s⁻¹, a dynamic balance between work hardening and dynamic softening is achieved, and the post-peak flow stress gradually stabilizes. At a high strain rate of 10 s⁻¹, the flow stress continues to decrease because the competition between softening from dynamic recrystallization and work hardening is disrupted by deformation-induced heating. Low strain rates (≤0.01 s⁻¹) and high temperatures (≥470 °C) promote dynamic recrystallization and significant grain refinement. Two optimal processing windows were determined: 400 to 430 °C at 0.001 to 0.01 s⁻¹, giving fully recrystallized fine equiaxed grains, and 440 to 460 °C at 0.01 to 0.1 s⁻¹ with a power dissipation efficiency η of 0.43 to 0.51, balancing processing efficiency and microstructural uniformity. This work provides systematic theoretical and data support for optimizing hot forming parameters of large Mg-Gd-Y-Zr load-bearing components and offers guidance for applying high-strength magnesium alloys in high-end equipment. Full article

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

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17 pages, 2798 KB

Open AccessArticle

Domain-Knowledge-Guided Feature Engineering for Small-Sample Machine Learning Prediction of Mechanical Properties in Low-Carbon Hot-Rolled Steel Strips

by Saurabh Tiwari, Hyoju Ahn, Jongwon Lee and Nokeun Park

Metals 2026, 16(8), 933; https://doi.org/10.3390/met16080933 - 21 Aug 2026

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Abstract

Industrial steel property prediction is often constrained by limited labelled data, reducing the effectiveness of conventional machine learning models. This study investigated whether metallurgy-informed feature engineering enhances predictive performance under small-data conditions. A representative set of 300 samples from an industrial low-carbon hot-rolled [...] Read more.

Industrial steel property prediction is often constrained by limited labelled data, reducing the effectiveness of conventional machine learning models. This study investigated whether metallurgy-informed feature engineering enhances predictive performance under small-data conditions. A representative set of 300 samples from an industrial low-carbon hot-rolled steel strip dataset (C: 0.02–0.06 wt%; Mn: 0.17–0.38 wt%) was used to derive five physically meaningful descriptors: carbon equivalent (CE), nitrogen-to-aluminum ratio (N/Al), microalloying efficiency index (MEI), thermal processing parameter (TPP), and solid solution strengthening index (SSSI). These descriptors were combined with the original 17 compositional and processing variables to create a 22-feature dataset. Random Forest (RF) and Extreme Gradient Boosting (XGBoost) models were evaluated on an independent 60-sample test set using 5-fold cross-validation. Feature engineering improved the prediction accuracy, with the greatest gain observed for elongation. For XGBoost, the mean percentage error decreased from 3.23% to 3.05%, whereas the test-set R² increased from 0.4935 to 0.5444, representing a 10.3% improvement in the explained variance. For the yield strength, the Random Forest method increased the R² from 0.4744 to 0.4861. Permutation importance and partial dependence analyses identified MEI and TPP as the six most influential predictors across all targets, confirming that the engineered descriptors provide complementary metallurgical information. Learning curve analysis showed slightly higher cross-validation R² values at intermediate training sizes (n = 125–175), indicating modestly improved sample efficiency. These findings establish domain-informed feature engineering as an interpretable and practical strategy for improving machine learning in data-limited steel manufacturing processes. Full article

(This article belongs to the Special Issue Advances in Metal Casting and Forming)

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27 pages, 12874 KB

Open AccessArticle

Influence and Mechanism of Microstructure Refinement on the Hydrogen Embrittlement Resistance of 34MnB5

by Yi Feng, Guangjie Huang, Kejian Li, Wei Li, Hongzhou Lu, Cansheng Yu, Hui Song, Jianing Bao, Junping Zhang and Jie He

Metals 2026, 16(8), 932; https://doi.org/10.3390/met16080932 - 21 Aug 2026

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Abstract

To investigate the effect of microalloying on hydrogen embrittlement resistance of hot-stamped steels with strength levels of 1.8 GPa and above, six composition schemes were designed based on conventional 34MnB5 steel, including three routes, namely Nb, V, and Nb–V. U-bend constant-strain bending tests [...] Read more.

To investigate the effect of microalloying on hydrogen embrittlement resistance of hot-stamped steels with strength levels of 1.8 GPa and above, six composition schemes were designed based on conventional 34MnB5 steel, including three routes, namely Nb, V, and Nb–V. U-bend constant-strain bending tests and slow strain rate tensile (SSRT) tests were conducted on quenched specimens for each scheme. Results indicated that the Nb-containing compositions exhibited superior hydrogen embrittlement resistance. The mechanism by which microalloying refines the martensitic microstructure of 34MnB5 in the quenched state and enhances its resistance to hydrogen embrittlement was studied in detail. It was found that Nb exhibits stronger effects than V in refining and homogenizing the martensite structure. The fundamental reasons for Nb’s enhanced ability to pin austenite grain boundaries at high temperatures—leading to better microstructural refinement and homogenization—are its higher temperature range for second-phase precipitation, greater driving force for grain boundary diffusion, lower austenite grain boundary diffusion coefficient, and weaker tendency for high-temperature coarsening of precipitates. The microstructural refinement and homogenization induced by Nb addition are more pronounced than those achieved by combined additions of Nb and V. Furthermore, within the concentration range of 0–0.1%, the amount of Nb is positively correlated with the degree of microstructural refinement and homogenization. By reducing martensite lath size through microalloying, multiple microstructural modifications occur: decreased density of geometrically necessary dislocations (GNDs) in the matrix, significant increase in interface density—especially a higher proportion of high-angle grain boundaries—reduced number of Σ3 special harmful grain boundaries, weakened matrix texture intensity, fewer twin martensites, and smaller twin martensite sizes. These factors collectively contribute significantly to the improved hydrogen embrittlement resistance of Nb-containing steels. Full article

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13 pages, 8899 KB

Open AccessArticle

Structure and Properties of the Melt-Spun Zr–(Al)–Ni–Cr–Ag Alloys

by Olena Shved, Vasyl Girzhon, Oleksandr Smolyakov, Ihor Shtablavyi, Philipp Dörflinger, Helmut Riedl, Andrey Prokofiev and Stepan Mudry

Metals 2026, 16(8), 931; https://doi.org/10.3390/met16080931 - 21 Aug 2026

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Abstract

The structure, mechanical and electrical properties of Zr-based melt-spun Zr–(Al)–Ni–Cr–Ag alloys were investigated as a function of elemental composition. X-ray diffraction reveals the structural evolution from fully amorphous to nanocrystalline states, with the latter containing Zr₂Ni “big-cube” (space group Fd3̄ [...] Read more.

The structure, mechanical and electrical properties of Zr-based melt-spun Zr–(Al)–Ni–Cr–Ag alloys were investigated as a function of elemental composition. X-ray diffraction reveals the structural evolution from fully amorphous to nanocrystalline states, with the latter containing Zr₂Ni “big-cube” (space group Fd3̄m, cF96), fcc-Zr₂Ni, and β-Zr phases depending on the alloying ratio: Cr-rich compositions (≥15 at.%) stabilize β-Zr within the amorphous matrix, whereas Ag-enriched alloys promote “big-cube” phase formation. Ag atoms can replace both Zr and Ni sites in the “big-cube” lattice, yielding a (Zr,Ag)₂(Ni,Ag) solid solution and highlighting its role as a structural bridge between the amorphous and crystalline states. Nanoindentation measurements show that hardness increases from 6.5 GPa in fully amorphous ribbons to 10.12 GPa in three-phase nanocrystalline composites, with an H/E ratio of ~0.08 indicating predominantly covalent bonding, and the fracture strength of the amorphous alloys is ~2 GPa, exceeding literature values for related Zr-based systems. Electrical resistivity measurements over the 4–298 K range show that most alloys deviate from Matthiessen’s rule, exhibiting a negative temperature coefficient of resistivity consistent with the Mooij correlation; the presence of the icosahedrally ordered “big-cube” phase further increases resistivity relative to fully amorphous alloys. Full article

(This article belongs to the Topic Alloys and Composites Corrosion and Mechanical Properties, 2nd Edition)

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15 pages, 4323 KB

Open AccessArticle

The Preparation and Optoelectronic Properties of Symmetric and Asymmetric Multilayered Transparent Conductive Films with ZnS-TiO₂-Ag Material System

by Kai Tao, Hanbin Chen, Fangzi Zhao, Shiqi Li and Zhiyong Liu

Metals 2026, 16(8), 930; https://doi.org/10.3390/met16080930 - 20 Aug 2026

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Abstract

Flexible transparent conductive films with symmetric and asymmetric multilayered structures are studied using the ZnS–TiO₂–Ag material system, in order to capitalize on the divergent properties of the two dielectric layers for improved performance. The dielectric/metal/dielectric-structured films were deposited by magnetron sputtering [...] Read more.

Flexible transparent conductive films with symmetric and asymmetric multilayered structures are studied using the ZnS–TiO₂–Ag material system, in order to capitalize on the divergent properties of the two dielectric layers for improved performance. The dielectric/metal/dielectric-structured films were deposited by magnetron sputtering sequentially, with high-purity targets. Multilayered films with various dielectric combinations and metallic layer thicknesses were prepared and analyzed. The surface morphology and phase structure were characterized by atomic force microscopy and scanning electronic microscopy. The optical properties were tested by spectrophotometry and analyzed by numerical simulation approach. The sheet resistance was measured via a four-point probe tester. Among the series of multilayers, asymmetric ZnS/Ag/TiO₂ film with 35 nm thickness of dielectric layers and 8.5 nm of metallic layer possesses the optimum comprehensive optoelectronic performance. The average light transmittance reaches 90.72% in the visible spectrum, and the sheet resistance is 7.69 Ω/sq. The good result is ascribed primarily to the combined advantages of superior percolation effect of bottom ZnS layer on ultrathin Ag layer, beneficial impingement effect of top layer deposition on the metallic layer, and excellent surface smoothness of the top dielectric layer. Full article

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20 pages, 4444 KB

Open AccessArticle

Investigation of the Structural State of a Liquid Mg–Zn Magnesium Alloy from the Perspective of the Behavior of the Bjerrum–Guggenheim Osmotic Coefficient in the Melt

by Vera Tolokonnikova, Sailaubai Baisanov, Amankeldy Ahmetov, Yerbolat Makhambetov, Olzhas Kenzhaliyev and Alexey Orlov

Metals 2026, 16(8), 929; https://doi.org/10.3390/met16080929 - 20 Aug 2026

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Abstract

Carrying out a series of fundamental studies in the field of physicochemical analysis, based on an approach that considers the phase state of alloys and accounts for the regular patterns of interaction of substances in multicomponent ores that are complex in both chemical [...] Read more.

Carrying out a series of fundamental studies in the field of physicochemical analysis, based on an approach that considers the phase state of alloys and accounts for the regular patterns of interaction of substances in multicomponent ores that are complex in both chemical and phase composition, makes it possible to formulate a number of scientifically substantiated practical recommendations. The aim of this work is to assess the degree of zinc sublimation from a magnesium alloy through the behavior of the Bjerrum–Guggenheim osmotic coefficient and the degree of dissociation of the congruent compound. The paper presents a method for processing phase equilibrium lines in a temperature–composition phase diagram, resulting in mathematical expressions for the liquidus and solidus lines on a unified analytical basis in the form of a semi-empirical dependence derived from the Schröder–Le Chatelier equation. Indirectly, through the Bjerrum–Guggenheim osmotic coefficient, the degree of dissociation of MgZn₂ in the Mg–Zn system was determined to range from 17% to 46%. This result is in good agreement with the conclusions of Nikolay Semyonovich Kurnakov regarding the degree of dissociation of congruent compounds inferred from the shape of the maximum on phase diagrams. For MgZn₂, this maximum is very smooth, i.e., the composition of the liquid phase changes continuously with deviation from stoichiometry, resulting in a symmetrical rounded peak. An experimental study was carried out using a SEM/EDS analytical complex to confirm the high volatility of zinc. The key zinc-concentrating phases were identified in the investigated processing products (slag, metal, and dust), which is consistent with the theoretical premises and explains the mechanism of zinc behavior during high-temperature processing of zinc-containing slags. The form of zinc occurrence in different phases was established. In the initial slag, the zinc content reaches 51.79%. In the metallic phase, zinc is detected as fine dispersed inclusions. In the collected dust (flue ducts), particles enriched in zinc up to 44.09 wt.% were identified. Full article

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29 pages, 23354 KB

Open AccessArticle

Industrial Waste Upcycling for Modern Construction: SAW Slag-Incorporated Composites with Multifunctional Properties Against Biological Degradation

by Samuel Castro-Lopes, Ivanilda Ramos de Melo, Viviane Drumond Rodrigues, José Anselmo da Silva Neto, Emanoel Araújo, Marcelo Medeiros, Severino Leopoldino Urtiga Filho, Tiago Felipe de Abreu Santos, Cinthia Pederneiras and Romildo Berenguer

Metals 2026, 16(8), 928; https://doi.org/10.3390/met16080928 - 20 Aug 2026

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Abstract

This research investigates the potential for valorizing submerged arc welding (SAW) slag as a partial substitute for Portland cement in eco-efficient mortars. The research focuses on microstructural characterization, mechanical performance, and, innovatively, resistance to microbial adhesion by Escherichia coli. The residue was [...] Read more.

This research investigates the potential for valorizing submerged arc welding (SAW) slag as a partial substitute for Portland cement in eco-efficient mortars. The research focuses on microstructural characterization, mechanical performance, and, innovatively, resistance to microbial adhesion by Escherichia coli. The residue was processed by grinding and incorporated at substitution levels of 5%, 10%, and 15% by weight. The mechanical results demonstrate that the 5% substitution (AM5%) showed the best performance, reaching 47.55 MPa at 28 days, an increase of approximately 20% compared to the reference sample. This improvement is attributed to the pozzolanic effect with the filling and refinement of the pore structure, in the production of the secondary C-A-S-H phase. In the bioreactor biological assay, the AM5% sample demonstrated a significant reduction in bacterial colonization adhering to the material’s surface, with values of 9.4 × 10¹ CFU/cm². Scanning electron microscopy (SEM) analyses revealed that the denser surface, with lower porosity, hindered the anchoring of E. coli and the formation of biofilm. The study concludes that the use of 5% SAW slag not only improves the structural properties of mortars but also increases their durability in environments prone to biological contamination, such as sanitation systems, promoting a sustainable alternative for the management of industrial waste in civil construction. Full article

(This article belongs to the Special Issue Pyrometallurgy and Waste Recycling: Experiment and Simulation)

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22 pages, 3896 KB

Open AccessArticle

Pellet-Sintering Process for Limonitic Nickel Laterite: Effects of Operating Parameters and Performance Improvement

by Gen Li, Deqing Zhu, Jian Pan, Qingshi Song, Wei Liu and Ming Wang

Metals 2026, 16(8), 927; https://doi.org/10.3390/met16080927 - 20 Aug 2026

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Abstract

Limonitic nickel laterite is difficult to sinter because of its high loss on ignition, high combined-water content, and complex refractory mineral composition, which often result in poor sinter strength and high solid fuel consumption. In this study, a pellet-sintering process was adopted to [...] Read more.

Limonitic nickel laterite is difficult to sinter because of its high loss on ignition, high combined-water content, and complex refractory mineral composition, which often result in poor sinter strength and high solid fuel consumption. In this study, a pellet-sintering process was adopted to improve the sintering performance of limonitic nickel laterite. Pot sintering tests were carried out to investigate the effects of key process parameters—including moisture content, solid fuel dosage, return fines dosage, and drying–holding regime—on yield, tumble index, productivity index, and solid fuel consumption. The selected conditions were determined as follows: moisture content of 21%, solid fuel dosage of 5.8%, return fines dosage of 25%, drying at 450 °C for 5 min, and holding at 1000 °C for 10 min, under a fixed basicity of 1.5 and a bed height of 850 mm. Under these conditions, the yield, tumble index, productivity index, and solid fuel consumption reached 70.19%, 57.87%, 1.37 t·m⁻²·h⁻¹, and 95.86 kg·t⁻¹, respectively. Compared with conventional sintering, pellet sintering increased the yield, tumble index, and productivity index by 24.05%, 35.56%, and 31.73%, respectively, while reducing solid fuel consumption by 22.87%. XRD, OM, quantitative image analysis, and SEM–EDS analyses showed that pellet sintering reduced the average two-dimensional pore area fraction from 33.29% to 18.05% and the large-pore area fraction from 22.25% to 11.61%, while promoting a more continuous bonding structure characterized by a spinel-rich mineral framework, spinel–olivine eutectic-type composite bonding phases, and SFCA-type bonding phases. These results demonstrate that pellet sintering is a feasible route for improving the sintering performance and consolidation behavior of limonitic nickel laterite. Full article

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20 pages, 5785 KB

Open AccessArticle

Mechanical Response Characteristics of Tungsten-Based Alloys Prepared by SLM: Experimental Research and Verification

by Yiming Li, Bihui Hong and Wenbin Li

Metals 2026, 16(8), 926; https://doi.org/10.3390/met16080926 - 20 Aug 2026

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Abstract

This study presents a systematic investigation into the mechanical responses of two tungsten-based alloys—84W–11.2Ni–4.8Fe and 88W–8.4Ni–3.6Fe—fabricated via selective laser melting (SLM). Quasi-static compression tests using a universal testing machine and dynamic impact experiments employing a split Hopkinson pressure bar (SHPB) were conducted over [...] Read more.

This study presents a systematic investigation into the mechanical responses of two tungsten-based alloys—84W–11.2Ni–4.8Fe and 88W–8.4Ni–3.6Fe—fabricated via selective laser melting (SLM). Quasi-static compression tests using a universal testing machine and dynamic impact experiments employing a split Hopkinson pressure bar (SHPB) were conducted over a temperature range of 298–598 K and strain rates spanning from 1 × 10⁻³ s⁻¹ to 2.3 × 10³ s⁻¹. Both alloys exhibited significant strain-rate hardening and thermal softening effects. Based on the experimental data, a Johnson–Cook (J–C) constitutive model was established. The fidelity of the calibrated model for the 84W alloy was rigorously validated through pulsed X-ray radiography and static armor penetration tests. The SLM-fabricated 84W-shaped charge liner produced a well-collimated jet with a tip velocity of 5101.5 m/s and achieved a penetration depth of 87 mm into rolled homogeneous armor (RHA)-equivalent steel targets. Numerical simulations using the developed J–C model showed close agreement with experimental measurements, with a maximum discrepancy of only 9.19%, thereby confirming the predictive capability of the constitutive model. These results demonstrate that the proposed J–C model can reliably characterize the large-deformation behavior of SLM-processed 84W and 88W liners under the extreme thermomechanical conditions characteristic of shaped charge jet formation—namely high temperature, high pressure, and ultra-high strain rate. Collectively, this work establishes a foundational framework for the application of SLM technology to shaped charge liner design and provides a critical basis for further research into jet formation physics and penetration mechanics of tungsten-based alloys. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing of Metallic Materials: Characterization, Properties and Applications)

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16 pages, 3970 KB

Open AccessArticle

Effect of Microalloying Elements on the Microstructure and Elevated-Temperature Mechanical Behavior of High-Strength Drill Pipe Steel

by Yuguang Fan, Ning Li, Kaifeng Chen, Zhi You, Xinguo Liu, Lijuan Zhu, Chun Feng, Kai Zhang, Tian Wang and Hao Qu

Metals 2026, 16(8), 925; https://doi.org/10.3390/met16080925 - 19 Aug 2026

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Abstract

The mechanical behavior of S135 and V150 (Mo-V-Nb microalloyed) drill pipe steels was systematically investigated at room temperature (RT) and elevated temperatures (100–300 °C), alongside the microstructural evolution after long-term thermal exposure at 310 °C (200–500 h). V150 steel exhibits a superior RT [...] Read more.

The mechanical behavior of S135 and V150 (Mo-V-Nb microalloyed) drill pipe steels was systematically investigated at room temperature (RT) and elevated temperatures (100–300 °C), alongside the microstructural evolution after long-term thermal exposure at 310 °C (200–500 h). V150 steel exhibits a superior RT yield strength (1099 vs. 1012 MPa) relative to S135, attributed to grain refinement and precipitation strengthening from nanoscale MC precipitates. However, at 200–300 °C, S135 steel displays strength recovery due to dynamic strain aging (DSA) facilitated by the formation of Cottrell atmospheres. Conversely, in V150 steel, V and Nb pin free interstitial atoms, suppressing Cottrell atmosphere formation and DSA. Consequently, V150 cannot gain DSA-induced strengthening, resulting in a steeper yield strength decline (a 17.3% drop at 300 °C versus 11.5% for S135). Long-term thermal exposure further reveals divergent microstructural evolution: S135 steel achieves synchronous improvements in strength and ductility via the transformation of coarse M₃C into stable alloy carbides and the precipitation of nanoscale Mo-enriched carbides. In contrast, V150 steel undergoes Ostwald ripening and coherency loss of high-volume-fraction nano-MC precipitates, weakening dislocation pinning and accelerating dislocation annihilation, ultimately leading to the simultaneous degradation of strength and ductility. This study elucidates that while Mo-V-Nb microalloying enhances RT strength, it compromises high-temperature mechanical stability. Full article

(This article belongs to the Section Metal Failure Analysis)

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26 pages, 7223 KB

Open AccessArticle

Sequential Design, Statistically Informed Multi-Objective Decision-Making, and Multi-Scale Quality Evaluation of Resistance Spot Welding Between Al-Si-Coated B1500HS and HC340/590DP Steels

by Wei Li and Liming Zhou

Metals 2026, 16(8), 924; https://doi.org/10.3390/met16080924 - 19 Aug 2026

Viewed by 443

Abstract

Dissimilar resistance spot welding of Al-Si-coated B1500HS hot-stamped steel to HC340/590DP dual-phase steel suffers from a narrow process window and HAZ temper softening. A sequential orthogonal-central composite design strategy screened factors and constructed local second-order models for nugget diameter and tensile-shear force. Because [...] Read more.

Dissimilar resistance spot welding of Al-Si-coated B1500HS hot-stamped steel to HC340/590DP dual-phase steel suffers from a narrow process window and HAZ temper softening. A sequential orthogonal-central composite design strategy screened factors and constructed local second-order models for nugget diameter and tensile-shear force. Because the complete tensile-shear CCD dataset is unavailable for independent verification, the tensile-shear model is used strictly as an auxiliary local calibration and is not assigned the same validation level as the nugget-diameter model. Within-batch ANOVA showed that electrode force dominated diameter variation and first-pulse current dominated force variation. A model-assisted variance-aware compromise (7.8/8.5 kA, 2.9 kN, 13/17 cycles) was point-wise validated at 6.5065 ± 0.1366 mm and 15.053 ± 0.1899 kN (n = 20, CV 2.10%/1.26%). The measured performance-optimal orthogonal condition remained Run 11; thus, the compromise is interpreted as a stability-oriented choice rather than a global optimum. A joint-specific HAZ screening envelope (width < 0.7 mm; hardness loss < 50%) is proposed as a descriptive screening criterion only; because HAZ width and microhardness were not measured for the n = 20 validation condition, the envelope was not validated on that condition and remains conditional on the single-factor HAZ data. The framework integrates process optimization with transparent statistical qualification and reports its model calibration limits. Full article

(This article belongs to the Section Welding and Joining)

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20 pages, 19002 KB

Open AccessArticle

Effects of Joint-Edge Preparation on Weld Quality and Mechanical Properties of Thin AISI 304 Stainless Steel Sheets Under Autogenous and Filler-Wire Laser Beam Welding Conditions

by Yeongsu Ha, Seung Yong Lee, Bong Cheon Park, Su Hwan Kim and Jung Kwan Seo

Metals 2026, 16(8), 923; https://doi.org/10.3390/met16080923 - 19 Aug 2026

Viewed by 269

Abstract

Laser beam welding (LBW) offers low thermal distortion for thin austenitic stainless steel sheets but is sensitive to butt-joint fit-up and edge quality. This study compared machined and sheared joint edges under selected autogenous and ER308L filler-wire LBW conditions. Bead geometry, defects, microstructure, [...] Read more.

Laser beam welding (LBW) offers low thermal distortion for thin austenitic stainless steel sheets but is sensitive to butt-joint fit-up and edge quality. This study compared machined and sheared joint edges under selected autogenous and ER308L filler-wire LBW conditions. Bead geometry, defects, microstructure, microhardness, tensile properties, and fracture behavior were characterized using conventional microscopy, EBSD-KAM, and three-dimensional digital image correlation (3D-DIC). The machined-edge autogenous condition (LBW-A-M) produced a stable bead with 0.04 mm top underfill and only a small number of internal discontinuities, while its tensile properties remained close to those of the base metal and fracture occurred in the base metal. In contrast, the sheared-edge autogenous condition (LBW-A-S) exhibited 0.24 mm top underfill, 0.18 mm misalignment, multiple pores, and localized strain near the weld, with tensile strength and elongation of 682.31 MPa and 44.04%, respectively. Under the selected filler-wire conditions, no measurable top underfill was observed, although pores remained. Because the autogenous and filler-wire modes used different process parameters and heat inputs, cross-mode differences are condition-specific rather than isolated filler-wire effects. Overall, joint-edge preparation and fit-up control remained important for thin-sheet LBW. Full article

(This article belongs to the Section Welding and Joining)

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18 pages, 22731 KB

Open AccessArticle

Synergistically Enhanced Bifunctional Electrocatalysis on W-Se Co-Modified Lightweight Porous Ni/Cu Foil for Methanol and Urea Oxidation

by Guangya Hou, Jingnan Wei, Jianli Zhang, Qiang Chen and Yiping Tang

Metals 2026, 16(8), 922; https://doi.org/10.3390/met16080922 - 19 Aug 2026

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Abstract

The development of lightweight, low-cost, and high-performance non-precious metal electrocatalytic electrodes is critical to advancing the practical implementation of methanol and urea oxidation reactions (MOR and UOR) in next-generation energy conversion systems. Herein, we reported a facile synthesis of a W-Se co-modified porous [...] Read more.

The development of lightweight, low-cost, and high-performance non-precious metal electrocatalytic electrodes is critical to advancing the practical implementation of methanol and urea oxidation reactions (MOR and UOR) in next-generation energy conversion systems. Herein, we reported a facile synthesis of a W-Se co-modified porous Ni/Cu paper electrode (W-NiSe/Cu_p) via synchronous pulse electrodeposition onto filter paper-derived porous Cu foil. The hierarchical porosity and high specific surface area originated from the paper template, while synergistic electronic modulation among Ni, W, and Se enhanced intrinsic catalytic activity. At 0.8 V, the W-NiSe/Cu_p electrode delivered current densities of 298 mA·cm⁻² (MOR) and 305 mA·cm⁻² (UOR) with a lower-mass loading, representing 1.29-fold and 1.34-fold enhancements over the Ni/Cu_p electrode. Furthermore, the electrode exhibited exceptional durability: under chronopotentiometry operation at 100 mA·cm⁻² in a 6-fold-concentrated electrolyte (6 M KOH + 3.0 M CH₃OH + 1.98 M CO(NH₂)₂), the operating potentials retained 95.74% (MOR) and 118.05% (UOR) of their initial values after 9 h. This study offers a novel strategy for designing lightweight non-precious metal catalytic electrodes for portable energy devices and also verifies the broad potential of biomass templates in constructing advanced energy electrocatalytic materials. Full article

(This article belongs to the Special Issue Energy Storage and Electrochemical Performance of Metals)

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13 pages, 12092 KB

Open AccessArticle

Viscous Flow Properties and Structural Evolution of Vanadium-Containing Hot Metal: Experiments and Molecular Dynamics Simulation

by Jiawei Chen, Yufei Pan, Penghui Guo, Xinyi Li, Zhuogang Pang, Zhenghua Shen, Shan Ren, Donghui Wei and Xiangdong Xing

Metals 2026, 16(8), 921; https://doi.org/10.3390/met16080921 - 19 Aug 2026

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Abstract

To reveal the effect of vanadium content on the viscous flow behavior of vanadium-containing hot metal, viscosity measurements and molecular dynamics simulations were conducted. The viscosity and melting characteristic temperature were measured. The local structures of Fe, V, and C atoms were analyzed [...] Read more.

To reveal the effect of vanadium content on the viscous flow behavior of vanadium-containing hot metal, viscosity measurements and molecular dynamics simulations were conducted. The viscosity and melting characteristic temperature were measured. The local structures of Fe, V, and C atoms were analyzed using radial distribution functions, average coordination numbers, mean square displacements, and cluster evolution. Both viscosity and melting characteristic temperature increased with vanadium content. At 1300 °C, the viscosity increased from 11.8 to 19.9 mPa·s as the vanadium content increased from 0.20 to 0.30 wt%. The melting characteristic temperature increased from 1242 to 1323 °C. Structural analysis showed that increasing vanadium content promoted the redistribution of C atoms. The average coordination number of V–C increased from 7.780 to 8.218. In contrast, the coordination numbers of C–Fe and Fe–C decreased. The mean square displacements of Fe and C atoms also decreased, indicating that atomic diffusion was suppressed. Cluster evolution further showed that V–C structures could dissociate and recombine with Fe–C and Fe–V units. Therefore, increasing vanadium content reduced the fluidity of hot metal by increasing the melting characteristic temperature, strengthening V–C local coordination, and promoting complex cluster formation. Full article

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11 pages, 4735 KB

Open AccessArticle

Low-Oxygen and Dense Mo10Cr Alloys Prepared via In-Situ Nanocarbon Deoxygenation and Two-Step Pressurization Hot Pressing

by Zixuan Liu, Xin Chen, Chengduo Wang, Hao Shi, Yanghan Li, Jiaqiang Yang, Ning Luo, Qingkui Li, Benshuang Sun and Jilin He

Metals 2026, 16(8), 920; https://doi.org/10.3390/met16080920 - 18 Aug 2026

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Abstract

Hot pressing is a promising technique for fabricating high-density molybdenum (Mo) alloys; however, obtaining low oxygen content remains a significant challenge. In this study, Mo10Cr alloy billets were prepared by hot pressing with nanocarbon addition and a two-step pressurization strategy to reduce the [...] Read more.

Hot pressing is a promising technique for fabricating high-density molybdenum (Mo) alloys; however, obtaining low oxygen content remains a significant challenge. In this study, Mo10Cr alloy billets were prepared by hot pressing with nanocarbon addition and a two-step pressurization strategy to reduce the oxygen content. Results show that the relative density of the Mo10Cr alloy increases with hot-pressing temperature and eventually remains above 98%, accompanied by grain growth and an increased degree of solid solution. The incorporation of nanocarbon facilitates in situ oxygen reduction during hot pressing under one-step pressurization, but this deoxygenation process is impeded by the applied pressure. In contrast, the two-step pressurization method effectively reduces the oxygen content of the nanocarbon-added Mo10Cr alloy to 169 ppm while maintaining a low residual carbon level. Furthermore, this approach significantly improves the compositional uniformity of the alloy. It is also observed that increasing the applied pressure promotes densification alongside grain growth. Consequently, the combination of two-step pressurization and in situ nanocarbon deoxygenation presents an effective pathway for fabricating dense, low-oxygen Mo alloys. Full article

(This article belongs to the Section Powder Metallurgy)

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18 pages, 7157 KB

Open AccessArticle

Thermal Simulation Experiments on Smelting Characteristics and Dephosphorization in Converter with High Scrap Ratio

by Chengyi Wang, Libin Yang, Wei Wu, Guangheng Ji, Yuxiang Dai, Guoqiang Wei and Zhouhua Jiang

Metals 2026, 16(8), 919; https://doi.org/10.3390/met16080919 - 18 Aug 2026

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Abstract

Smelting with a high scrap ratio in converters holds significant importance for carbon reduction and emission reduction in the iron and steel industry. Under high scrap ratio conditions, the kinetic and thermodynamic conditions of the molten bath change significantly, leading to considerable differences [...] Read more.

Smelting with a high scrap ratio in converters holds significant importance for carbon reduction and emission reduction in the iron and steel industry. Under high scrap ratio conditions, the kinetic and thermodynamic conditions of the molten bath change significantly, leading to considerable differences in the elemental reactions and slag formation patterns during the smelting process. To investigate the reaction characteristics and dephosphorization behavior of the molten bath under different scrap ratios, this study conducted thermal simulation experiments of converter smelting with four scrap ratios (20%, 30%, 40%, and 50%) using a 500 kg induction furnace. Scrap preheating and supplemental heating agents were applied as needed. Slag petrographic analysis was carried out using SEM and EDS. The experimental results indicate that with scrap ratios of 20% and 30%, the carbon–oxygen reaction and slag formation efficiency are relatively high. The dephosphorization rate in the early stage of smelting can exceed 50%, and phosphorus is effectively enriched in the CaO–SiO₂ matrix phase, with the highest phosphorus distribution ratio observed at a 30% scrap ratio. In contrast, with scrap ratios of 40% and 50%, the carbon–oxygen reaction is slower, and the dephosphorization rate in the early smelting stage is less than 10%. In the 40% scrap ratio experiment, phosphorus began to accumulate significantly in the dicalcium silicate phase during the mid-smelting stage as the basicity increased. At a 50% scrap ratio, the silicate matrix remained the dominant phase throughout all smelting stages, and no distinct phosphorus-rich phase was formed. Full article

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

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19 pages, 7288 KB

Open AccessArticle

Comparative Study of Cathodic Protection Effects on Corrosion and Biofouling of Bronze Alloys in Marine Environment and Laboratory Conditions

by Aiala Urbegain, Carlos G. San-Gabino, Antonio Santiago, Berta Antelo, Javier Franco and Iñigo Braceras

Metals 2026, 16(8), 918; https://doi.org/10.3390/met16080918 - 18 Aug 2026

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Abstract

Cathodic protection (CP) is used in the marine industry to prevent corrosion of metal components in seawater but may also promote biofilm formation. When steel and copper alloy components are in contact, the latter is often subjected to higher applied CP voltages than [...] Read more.

Cathodic protection (CP) is used in the marine industry to prevent corrosion of metal components in seawater but may also promote biofilm formation. When steel and copper alloy components are in contact, the latter is often subjected to higher applied CP voltages than otherwise required when a steel component is not present. In this study, the protection that CP offers in bronze alloys (RG-10 and CC492K) was assessed, both in controlled laboratory conditions and in real marine conditions in the Bay of Biscay (up to 3000 h), with various temperatures and methods: sacrificial anodes and impressed currents under different voltages. After the exposures, visual, scanning electron microscopy (SEM), X-ray diffraction (XRD) and corrosion rate analyses were performed. The results showed faster biofouling deposition on surfaces with a higher CP voltage, exposed to marine seawater, at the early stages. Subsequently, for longer exposure times, intermediate CP voltages offered less biofouling protection. XRD analyses showed the presence of calcareous compounds (calcite and aragonite), among others. Meanwhile, the corrosion observed in the laboratory was mediated by the amounts of deposited salts, with higher corrosion corresponding to higher CP voltages. Changes in temperature for the same CP voltage caused quantitative and qualitative differences in salt deposition. The higher Pb content of the CC492K alloy compared with the higher Cu and Sn contents of GR-10 did not manifest at the biofouling level, but different corrosion rates were measured (GR-10 < CC492K). Thus, the optimal CP protection conditions for marine and laboratory environments are not the same, because of the different conditions involved. Full article

(This article belongs to the Special Issue Marine Environmental Corrosion and Protection of Metals)

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21 pages, 3988 KB

Open AccessArticle

Study on Interfacial Characteristics and Tribological Behavior of Laser Cladding Ni/WC Coating

by Linghui Kong, Lei Zhang, Yi Li, Hushtarbek Mametimin, Xuyang Liu and Jiabing Lei

Metals 2026, 16(8), 917; https://doi.org/10.3390/met16080917 - 17 Aug 2026

Viewed by 246

Abstract

Ni60/WC composite coatings reinforced with various WC contents were fabricated on 45 steels via high-speed laser cladding. First-principles calculations were adopted to investigate the interfacial characteristics between Ni and WC. The microstructures of the coating were analyzed by a scanning electron microscope (SEM). [...] Read more.

Ni60/WC composite coatings reinforced with various WC contents were fabricated on 45 steels via high-speed laser cladding. First-principles calculations were adopted to investigate the interfacial characteristics between Ni and WC. The microstructures of the coating were analyzed by a scanning electron microscope (SEM). The microhardness and wear resistance of the coatings were evaluated by a Vickers hardness tester and a friction and wear tester. Theoretical calculations indicate that the C-terminated WC (001) crystal plane achieves the most stable bonding with the Ni (111) surface through the hcp site, with an interface energy of 9.57 J·m⁻². The interface is mainly provided by Ni-W metal bonds and Ni-C covalent bonds. The microstructure results show that the WC particles have good metallurgical bonding with the Ni matrix. Thus, the good interface ensures efficient load transfer to hard WC particles. The microhardness rose markedly with the increase in WC content, reaching 760 HV_0.2 for the 40 wt.% WC, which is 1.8 times that of Ni60 coatings. Tribological experiments showed that appropriate WC content could significantly improve the wear resistance of the coating. Full article

(This article belongs to the Section Additive Manufacturing)

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16 pages, 4453 KB

Open AccessArticle

Relation Between Local Mechanical Properties and Microstructural Evolution of 9%Cr Welded Joint by Nanoindentation Characterization

by Yini She, Zhiqiang Wang, Linye Zhang, Zhibin Shen, Licheng Ruan and Yuxuan Song

Metals 2026, 16(8), 916; https://doi.org/10.3390/met16080916 - 16 Aug 2026

Viewed by 324

Abstract

In ultra-supercritical (USC) power plants, P92 steel welded joints are continuously subjected to creep-fatigue (CF) loading, rendering them susceptible to premature cracking during service. To investigate the CF interaction behavior, CF tests were performed on P92 steel welded joints at 650 °C under [...] Read more.

In ultra-supercritical (USC) power plants, P92 steel welded joints are continuously subjected to creep-fatigue (CF) loading, rendering them susceptible to premature cracking during service. To investigate the CF interaction behavior, CF tests were performed on P92 steel welded joints at 650 °C under various dwell times. The results indicate that prolonged dwell periods progressively shorten the cycle life. Scanning electron microscopy (SEM) observations reveal that with increasing dwell time, the fracture mechanism of the P92 steel gradually transitions from a fatigue-dominated failure mode to one governed by creep-fatigue interaction damage. Subsequently, nanoindentation was employed to evaluate the hardness (H), elastic modulus (E), and creep deformation, based on which the strain rate sensitivity (m) was estimated and the underlying damage mechanisms were thoroughly discussed. Full article

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16 pages, 9452 KB

Open AccessArticle

Enhanced Impact Toughness of 6082 Aluminum Alloy via Electromagnetic Shocking Treatment

by Qian Sun, Junzhong Zou and Qi Xiang

Metals 2026, 16(8), 915; https://doi.org/10.3390/met16080915 - 15 Aug 2026

Viewed by 234

Abstract

To further improve the impact toughness of aged 6082 aluminum alloy, electromagnetic shocking treatment (EST) was applied to IHC (solution treatment + unidirectional compression + peak aging) samples. The mechanical properties and impact toughness of the IHC and EST samples were evaluated through [...] Read more.

To further improve the impact toughness of aged 6082 aluminum alloy, electromagnetic shocking treatment (EST) was applied to IHC (solution treatment + unidirectional compression + peak aging) samples. The mechanical properties and impact toughness of the IHC and EST samples were evaluated through room-temperature tensile tests and Charpy impact tests, respectively. The results indicate that, compared to the IHC samples, the EST samples exhibit higher tensile strength (an increase of approximately 9.4%), greater elongation, and significantly higher impact energy (an increase of approximately 26.5%). Microstructural characterization reveals that, compared to the IHC samples, the EST samples possess a lower dislocation density, a larger grain size, and shorter precipitates. Striped grain boundaries were observed in both IHC and EST samples, but they were considerably more pronounced in the EST samples. This indicates that more distinct interface wetting occurred in the EST samples, which promoted grain growth to some extent, a reduction in dislocation density, precipitate dissolution, and the occurrence of interface bridging. This paper primarily investigates the microstructural evolution within the alloy under EST and discusses how these microstructural changes influence the alloy’s performance, thereby providing a novel approach to enhancing the impact toughness of aluminum alloys. Full article

(This article belongs to the Special Issue Advances in Lightweight Alloys, 3rd Edition)

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19 pages, 25446 KB

Open AccessArticle

Co-Pyrolysis of Waste Tennis Ball Rubber and Spent Lithium-Ion Batteries for Reductive Cathode Regeneration and Porous Carbon Production

by Qing Zhang, Jamile Mohammadi Moradian, Jiahao Li, Sabereh Nazari, Haifeng Wang and Yanping Zhang

Metals 2026, 16(8), 914; https://doi.org/10.3390/met16080914 - 14 Aug 2026

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Abstract

The rapid growth of tennis participation and the widespread use of lithium-ion batteries have led to increasing volumes of rubber waste and spent battery materials, underscoring the need for integrated recycling strategies. In this work, a thermochemical co-pyrolysis process is developed to convert [...] Read more.

The rapid growth of tennis participation and the widespread use of lithium-ion batteries have led to increasing volumes of rubber waste and spent battery materials, underscoring the need for integrated recycling strategies. In this work, a thermochemical co-pyrolysis process is developed to convert waste tennis ball rubber particles (TBRPs) and spent lithium-ion battery (LIB) cathodes into valuable products. The decomposition of TBRPs generates reactive gaseous and liquid hydrocarbons that function as in situ reductants, enabling the breakdown of high-valence transition metal oxides in the cathode material. Subsequent magnetic separation and mild acid-washing yield nonmagnetic solids enriched in lithium compounds and carbonaceous residues. Structural and chemical analyses (SEM, XRD, TEM, EDS, and XPS) confirm extensive cathode reduction and the formation of Li₂CO₃ at optimized conditions (650 °C, 1 h, cathode-to-TBRPs mass ratio 1:0.65). The carbonized rubber evolves into a highly porous carbon material with a carbon purity of approximately 95.37 At%. This study demonstrates a low-energy, environmentally friendly pathway for the co-valorization of two challenging waste streams while simultaneously recovering lithium salts, reduced metal oxides, and functional porous carbon. Full article

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28 pages, 5642 KB

Open AccessArticle

Depth-Resolved Surface Integrity Evolution and Hydrodynamic Erosion Mechanisms in Abrasive Water Jet Machining of Dissimilar Stainless Steel–Carbon Steel Welds

by Mohammad S. Alsoufi

Metals 2026, 16(8), 913; https://doi.org/10.3390/met16080913 - 14 Aug 2026

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Abstract

Abrasive Water Jet Machining (AWJM) is increasingly used for post-weld surface modification of dissimilar metallic joints; however, the depth-dependent surface response of welded stainless–carbon steel joints remains insufficiently quantified. In this study, four dissimilar welded systems, TIG 316, TIG 309, ARC 316, and [...] Read more.

Abrasive Water Jet Machining (AWJM) is increasingly used for post-weld surface modification of dissimilar metallic joints; however, the depth-dependent surface response of welded stainless–carbon steel joints remains insufficiently quantified. In this study, four dissimilar welded systems, TIG 316, TIG 309, ARC 316, and ARC 309, were systematically investigated to elucidate the combined influence of welding technology, filler composition, and jet parameters on surface integrity. Surface roughness was evaluated at multiple jet-penetration depths using amplitude (R_a, R_q, R_t, R_z) and statistical (R_sk, R_ku) descriptors. The results reveal three distinct hydrodynamic erosion regimes governing texture evolution. Duplex welds (TIG 309 and ARC 309) exhibited highly stable erosion behavior, with R_a confined to 1.91–2.99 µm, low roughness gradients (ΔR_a/Δdepth = 0.012–0.015 µm·mm⁻¹), and near-Gaussian surface statistics (R_sk ≈ 0, R_ku ≈ 3–4). In contrast, austenitic welds (TIG 316 and ARC 316) showed pronounced depth-dependent instability, with R_a increasing up to 4.54 µm and the normalized roughness ratio R_z/R_a reaching 5.69 in TIG 316 near the jet exit. Strong inter-parameter correlations in duplex welds (r ≥ 0.94) confirm uniform erosion kinetics, whereas weakened correlations in austenitic systems (r ≈ 0.70–0.83) reflect jet-energy dissipation. These findings establish a mechanistically grounded AWJM performance window for achieving R_a ≤ 3 µm in dissimilar welded steels. Full article

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18 pages, 27466 KB

Open AccessArticle

Numerical Investigation of Melt Flow and Free-Surface Deformation in an Industrial Dual-Mode Vacuum Induction Furnace

by Zhenchao Han, Di Wang, Qintian Zhu, Hao Qiu and Heping Liu

Metals 2026, 16(8), 912; https://doi.org/10.3390/met16080912 - 14 Aug 2026

Viewed by 362

Abstract

During vacuum induction melting (VIM) of superalloys, oxygen and nitrogen control involves interfacial processes at both the melt free surface and the crucible–melt interface, where melt flow is an important factor affecting reaction kinetics. A coupled electromagnetic and fluid flow model with a [...] Read more.

During vacuum induction melting (VIM) of superalloys, oxygen and nitrogen control involves interfacial processes at both the melt free surface and the crucible–melt interface, where melt flow is an important factor affecting reaction kinetics. A coupled electromagnetic and fluid flow model with a deformable free surface was developed and validated for a 3 t industrial VIM furnace with two electromagnetic excitation modes. The melt flow under the Heating and Stirring modes is compared, with particular attention to the role of free-surface deformation, and the effects of input power and filling ratio are further examined. The results show that at an input power of 190 kW and a filling ratio of 85%, the Heating mode produces two counter-rotating vortices separated by a low-velocity mid-region, while the Stirring mode generates a dominant upper vortex covering most of the melt volume with a smaller counter-rotating vortex at the bottom. The Stirring mode achieves approximately 1.3 times the surface velocity, 1.7 times the wall friction velocity, and half the mixing time of the Heating mode. Free-surface deformation significantly affects the predicted flow structure, particularly under the Heating mode. Parametric results further show that input power mainly changes the flow intensity without altering the flow structure under either mode. By contrast, the filling ratio strongly affects the flow structure under the Heating mode, while that under the Stirring mode is largely preserved. These findings provide insight into the melt flow conditions relevant to oxygen and nitrogen removal during VIM processing. Full article

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

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19 pages, 19396 KB

Open AccessArticle

Aluminosilicochrome Produced from Technogenic Wastes as an Alternative to Conventional Ferrosilicochrome in Refined Ferrochrome Smelting

by Aristotel Issagulov, Aibar Myrzagaliyev, Saule Sagintayeva, Yerbolat Makhambetov, Diana Issagulova and Kuanysh Ilyassov

Metals 2026, 16(8), 911; https://doi.org/10.3390/met16080911 - 14 Aug 2026

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Abstract

This study investigates the possibility of using aluminosilicochrome (ASC) produced from technogenic raw materials as a potential alternative to FSC-48 ferrosilicochrome in refined ferrochrome smelting. Laboratory smelting tests were carried out in an induction furnace using alumina crucibles with a charge mass of [...] Read more.

This study investigates the possibility of using aluminosilicochrome (ASC) produced from technogenic raw materials as a potential alternative to FSC-48 ferrosilicochrome in refined ferrochrome smelting. Laboratory smelting tests were carried out in an induction furnace using alumina crucibles with a charge mass of 50 g. The two variants were compared based on the material balance, SEM-EDS analysis of the metallic and slag phases, a conditional estimate of chromium transfer to the metal, and the results of thermodynamic modeling in FactSage 8.4. It was established that a Cr–Fe metallic phase is formed when both FSC-48 and ASC are used. The average metal mass was 13.8 g for FSC-48 and 13.3 g for ASC. According to SEM-EDS data, the Cr content in the metallic phase was 70.53 and 68.64 wt. %, respectively. Aluminum introduced with ASC predominantly transfers into the slag, increasing its Al content to 20.81 wt. %. The conditional estimate of total chromium transfer from the charge to the metallic phase was 91.9% for FSC-48 and 91.6% for ASC. FactSage modeling showed higher calculated ore-derived Cr recovery for ASC under equilibrium conditions; however, excessive ASC addition increased the Si content in the metal. The obtained results confirm the fundamental possibility of using ASC as a complex reductant in refined ferrochrome smelting. Full article

(This article belongs to the Section Extractive Metallurgy)

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14 pages, 29702 KB

Open AccessArticle

In Situ Investigation of Temperature and Strain-Rate-Dependent Serrated Flow and Crack Evolution in Mn13 High–Manganese Steel

by Ming Gao, Yang Liu, Yanling Zhang, Yaqiang Li, Qiang Liu and Lei Cheng

Metals 2026, 16(8), 910; https://doi.org/10.3390/met16080910 - 14 Aug 2026

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Abstract

Temperature- and strain-rate-dependent serrated flow, localized plastic instability, and qualitative microcrack evolution in Mn13 Hadfield steel were investigated using stress–strain analysis and in situ tensile observation. Solution treatment at 1050 °C for 1–1.5 h followed by water quenching yielded homogeneous single-phase austenite. Type [...] Read more.

Temperature- and strain-rate-dependent serrated flow, localized plastic instability, and qualitative microcrack evolution in Mn13 Hadfield steel were investigated using stress–strain analysis and in situ tensile observation. Solution treatment at 1050 °C for 1–1.5 h followed by water quenching yielded homogeneous single-phase austenite. Type A and Type B serrations were dominant at room temperature at 1 × 10⁻³ s⁻¹ and at 100 °C at 1 × 10⁻² s⁻¹, whereas the room-temperature specimen tested at 1 × 10⁻² s⁻¹ showed delayed serration onset and pronounced Type B stress drops only at high strains. Type C serrations occurred mainly near fracture at 100 °C at 1 × 10⁻³ s⁻¹, 200 °C at 1 × 10⁻² s⁻¹ and 200 °C at 5 × 10⁻² s⁻¹. In situ observations further reveal that different serration types correspond to distinct localized deformation modes. During Type A serrations, the tracked feature exhibited unidirectional stepwise migration involving forward motion, arrest, and renewed advance. Type B serrations were associated with discontinuous pulse-like migration characterized by rapid forward motion, brief arrest, local backward motion, and renewed advance. No regular trajectory was observed during Type C stress drops; only local brightness changes and slight positional shifts occurred. These observations link macroscopic serrations to localized deformation in Mn13 steel and provide qualitative in situ evidence for grain-boundary microcrack initiation and evolution during deformation. Full article

(This article belongs to the Special Issue Metal Material Failure Analysis and Optimization)

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13 pages, 3160 KB

Open AccessArticle

HAZ Evolution in PHS1500 and Q&P1180 Steels Under Resistance Spot Welding Thermal Cycles

by Maria Emanuela Palmieri, Matteo Villa, Giuseppe Macoretta, Michele Maria Tedesco and Luigi Tricarico

Metals 2026, 16(8), 909; https://doi.org/10.3390/met16080909 - 14 Aug 2026

Viewed by 326

Abstract

Resistance spot welding (RSW) is the primary joining technology for automotive advanced high-strength steels (AHSSs), where the inherent severe thermal cycles profoundly alter the heat-affected zone (HAZ) microstructure, leading to localized variations in mechanical properties. Characterizing the spatial gradients in microstructure and the [...] Read more.

Resistance spot welding (RSW) is the primary joining technology for automotive advanced high-strength steels (AHSSs), where the inherent severe thermal cycles profoundly alter the heat-affected zone (HAZ) microstructure, leading to localized variations in mechanical properties. Characterizing the spatial gradients in microstructure and the resulting mechanical properties remains a major challenge in weld failure analysis due to the small size of the HAZ and its complex thermal history. In this study, the HAZ of two prominent AHSS grades, a first-generation press hardening steel (PHS1500) and a third-generation quenching and partitioning steel (Q&P1180), was physically simulated using a Gleeble^® 3180 thermomechanical simulator to achieve precise control over the localized thermal cycles. The investigation first evaluated the role of thermal cycle duration, governed by the welding time parameter (300 ms vs. 800 ms), on the microstructural evolution of the PHS1500 steel. Increasing the weld time from 300 ms to 800 ms reduced the cooling rate under the nominal 1400 °C condition from approximately 3000 K/s to 2500 K/s; however, no marked change was observed in the overall microstructural and hardness trends within the investigated range. Subsequently, using the 300 ms thermal profile as a reference baseline, a comparative metallurgical study was conducted between PHS1500 and Q&P1180. Under the same 300 ms thermal history, the maximum hardness reduction relative to the corresponding base material was approximately 42% for PHS1500 and 12% for Q&P1180. The hardness minima were located within FE-estimated temperature ranges close to the Ac₁ region for PHS1500 and around 600 °C for Q&P1180, respectively. This comparison highlighted the distinct microstructural responses of the two generations across the upper-critical (UCHAZ), inter-critical (ICHAZ), and sub-critical (SCHAZ) zones. Moreover, microhardness profiles were correlated with the microstructural findings, establishing a correlation among the simulated thermal history, the observed microstructural evolution, and localized mechanical performance. Full article

(This article belongs to the Special Issue Recent Advances in Microstructure, Experiment and Numerical Simulation of Steel)

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Metals, Volume 16, Issue 8 (August 2026) – 117 articles

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