Metals

16 pages, 3232 KiB

Open AccessArticle

Multi-Model Collaborative Optimization of Inconel 690 Deposited Geometry in Laser-Directed Energy Deposition: Machine Learning Prediction and NSGA-II Decision Framework

by Chen Liu, Junxiao Liu, Xiuyuan Yin, Xiaoyu Zhang, Shuo Shang and Changsheng Liu

Metals 2025, 15(8), 905; https://doi.org/10.3390/met15080905 (registering DOI) - 14 Aug 2025

Abstract

The critical challenge of achieving precise geometric control in laser directed energy deposition (L-DED) of Inconel 690 for nuclear applications is addressed by this study. We established a data-driven optimization framework that reduces time-consuming trial-and-error experiments. A comprehensive process-geometry dataset was generated through [...] Read more.

The critical challenge of achieving precise geometric control in laser directed energy deposition (L-DED) of Inconel 690 for nuclear applications is addressed by this study. We established a data-driven optimization framework that reduces time-consuming trial-and-error experiments. A comprehensive process-geometry dataset was generated through full-factor experiments. Pearson correlation analysis revealed significant correlations: strong positive correlations between laser power and bead width (r = 0.82) and depth (r = 0.85), and between powder feed rate and height (r = 0.70). A hybrid machine learning model was subsequently developed. It used a Backpropagation Neural Network (BPNN) to achieve excellent prediction of width, height, and depth (R² ≤ 0.962). It also generated 100 uniformly distributed Pareto optimal process parameter sets via the Non-dominated Sorting Genetic Algorithm II (NSGA-II). Experimental validation confirmed the model’s high predictive accuracy—relative error ≤ 5% for width/depth, and a maximum relative error of 5.34% for height. This demonstrates the framework’s effectiveness for reliable multi-objective process optimization in high-precision deposition tasks. It also highlights its potential for use in nuclear component repair and other material systems. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing for Metallic Materials and Their Applications (3rd Edition))

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15 pages, 11276 KiB

Open AccessArticle

Influence of Casting Texture on Local Material Flow During ECAP of Commercially Pure Aluminum

by Nadja Berndt and Martin Franz-Xaver Wagner

Metals 2025, 15(8), 904; https://doi.org/10.3390/met15080904 (registering DOI) - 14 Aug 2025

Abstract

The plastic deformation during equal-channel angular pressing (ECAP) can be affected by various material- and processing-related factors. For instance, the initial crystal orientation and grain size play an important role in determining the material flow, which may cause localized deformation in terms of [...] Read more.

The plastic deformation during equal-channel angular pressing (ECAP) can be affected by various material- and processing-related factors. For instance, the initial crystal orientation and grain size play an important role in determining the material flow, which may cause localized deformation in terms of macroscopic deformation banding. In this study, we use a continuous cast AA1080 aluminum alloy with coarse columnar grains to analyze the influence of casting texture on the local material flow during ECAP. Billets are extracted with their columnar grains inclined either in the same direction as the ECAP shear plane or opposite to it. Visio-plastic analysis is performed on split billets. The pass is interrupted halfway through the ECAP tool to accurately capture steady-state deformation conditions. Flow lines at several positions within the billet are identified based on the positions of deformed and undeformed marker points and fitted to a phenomenological model based on a super-ellipse function. For further characterization, hardness measurements, optical and electron microscopy are carried out on the ECAP-deformed samples. Significant differences in terms of local material flow and microstructure evolution regarding the resulting crystal orientation and deformation banding are observed. Our results confirm and emphasize the importance of initial grain size and texture effects for ECAP processing. Full article

(This article belongs to the Special Issue Preparation, Formation and Application of Light Alloys and Their Composites)

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13 pages, 4949 KiB

Open AccessArticle

Preparation and Characterization of MnFe₂O₄/Fe Soft Magnetic Composites by Surface Oxidation

by Shigeng Li, Rutie Liu and Xiang Xiong

Metals 2025, 15(8), 903; https://doi.org/10.3390/met15080903 (registering DOI) - 14 Aug 2025

Abstract

MnFe₂O₄/Fe soft magnetic composites (SMCs) were designed by the surface oxidation method, and the MnFe₂O₄ layer was utilized as the insulation coating. The microstructure of SMCs and the chemical composition of the insulation layer were observed [...] Read more.

MnFe₂O₄/Fe soft magnetic composites (SMCs) were designed by the surface oxidation method, and the MnFe₂O₄ layer was utilized as the insulation coating. The microstructure of SMCs and the chemical composition of the insulation layer were observed using scanning electron microscopy and energy-dispersive spectroscopy. The surface phase composition of SMCs was characterized using X-ray diffraction, X-ray photoelectron spectrometry, and Raman spectroscopy. The effect of annealing temperature on the insulation layer was investigated, and its relationship with the magnetic properties of the MnFe₂O₄/Fe SMCs was explored. The best overall performances were obtained at 50 mT and 100 kHz with saturation magnetization M_s = 205 emu/g, amplitude permeability μ_a = 100, and a core loss of 234.9 W/kg. Therefore, this work can provide a method to develop a novel insulating coating to reduce core loss, which is of great significance to the investigation of other Fe-based soft magnetic composites for applications in high-frequency magnetic fields. Full article

(This article belongs to the Special Issue Metallic Nanostructured Materials and Thin Films)

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15 pages, 7895 KiB

Open AccessArticle

Microstructural Characteristics of WC-Cu Cladding on Mild Steel Substrate Prepared Through Plasma Transferred Arc Welding

by Muhammad Hussain, Bosheng Dong, Zhijun Qiu, Ulf Garbe, Zengxi Pan and Huijun Li

Metals 2025, 15(8), 902; https://doi.org/10.3390/met15080902 - 13 Aug 2025

Abstract

This study explores the development of a novel composite coating system combining the high hardness of WC and thermal conductivity of Cu, employing the plasma transfer arc welding method under ambient conditions. Utilizing an advanced welding approach, the work investigates microstructural evolution and [...] Read more.

This study explores the development of a novel composite coating system combining the high hardness of WC and thermal conductivity of Cu, employing the plasma transfer arc welding method under ambient conditions. Utilizing an advanced welding approach, the work investigates microstructural evolution and phase formation in a WC-Cu-based coating applied to a mild steel substrate. Emphasis is placed on understanding the solidification behaviour and its influence on defects, microstructural refinement, and carbide formation. The study provides insights into the interactions between coating constituents and the underlying substrate under controlled thermal conditions. These findings demonstrate the potential for producing functionally graded coatings tailored for demanding wear and heat dissipation applications. The approach offers a pathway for enhancing the durability and performance of steel components in extreme service environments. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Experiments and Modelling)

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14 pages, 3658 KiB

Open AccessArticle

Research on the Vector Coherent Factor Threshold Total Focusing Imaging Method for Austenitic Stainless Steel Based on Material Characteristics

by Tianwei Zhao, Ziyu Liu, Donghui Zhang, Junlong Wang and Guowen Peng

Metals 2025, 15(8), 901; https://doi.org/10.3390/met15080901 - 12 Aug 2025

Abstract

The degree of anisotropy and heterogeneity in coarse-grained materials significantly affects ultrasonic propagation behavior and scattering. This paper proposes a vector coherent factor threshold total focusing imaging method (VCF-T-TFM) for austenitic stainless steel, based on material properties, through a combination of simulation and [...] Read more.

The degree of anisotropy and heterogeneity in coarse-grained materials significantly affects ultrasonic propagation behavior and scattering. This paper proposes a vector coherent factor threshold total focusing imaging method (VCF-T-TFM) for austenitic stainless steel, based on material properties, through a combination of simulation and experimentation. Three types of austenitic stainless steel weld test blocks with varying degrees of heterogeneity were selected containing multiple side-drilled hole defects, each with a diameter of 2 mm. Full-matrix data were collected using a 32-element phased array probe with a center frequency of 5 MHz. The grain size and orientation of the material were quantitatively observed via electron backscatter diffraction (EBSD). By combining the instantaneous phase distribution of the TFM image, the coarse-grained material coherence compensation value (C_A) and probability threshold (P_T) were optimized for different heterogeneous regions, and the vector coherence imaging threshold (γ) was adjusted. The defect imaging results of homogeneous material (carbon steel) and three austenitic stainless steels with different levels of heterogeneity were compared, and the influence of coarse-grained, anisotropic heterogeneous structures on the imaging signal-to-noise ratio was analyzed. The results show that the VCF-T-TFM, which considers the influence of material properties on phase coherence, can suppress structural noise. Compared to compensation results that did not account for material properties, the signal-to-noise ratio was improved by 97.3%. Full article

(This article belongs to the Special Issue Non-Destructive Testing of Metallic Materials)

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11 pages, 5053 KiB

Open AccessArticle

The Influence of Microcracks Generated During Forging on Crack Propagation in Steel Forgings

by Marek Grega and Janette Brezinová

Metals 2025, 15(8), 900; https://doi.org/10.3390/met15080900 - 12 Aug 2025

Abstract

This article investigates the formation of solidification cracks in steel forgings used for bearing rings in gear reducers of robotic arms. The forging and heat treatment processes, conducted under consistent technological conditions, revealed the occurrence of high-temperature annealing cracks caused by plasticity depletion [...] Read more.

This article investigates the formation of solidification cracks in steel forgings used for bearing rings in gear reducers of robotic arms. The forging and heat treatment processes, conducted under consistent technological conditions, revealed the occurrence of high-temperature annealing cracks caused by plasticity depletion during stress relaxation. Additionally, solidification cracks were analyzed, with chemical compositions and hardness measurements indicating susceptibility due to elevated carbon and chromium content, as well as a high cracking parameter. Die tool wear and damage during forging were identified as key contributors to crack formation, transferring surface defects, inclusions, and creating cracks that propagate during subsequent processing. The findings underscore the influence of the tooling conditions, material properties, and process parameters on the quality and reliability of steel forgings. Full article

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15 pages, 3120 KiB

Open AccessArticle

Effect of Cu and Ag Content on the Electrochemical Performance of Fe40Al Intermetallic Alloy in Artificial Saliva

by Jesus Porcayo-Calderon, Roberto Ademar Rodriguez-Diaz, Jonathan de la Vega Olivas, Cinthya Dinorah Arrieta-Gonzalez, Jose Gonzalo Gonzalez-Rodriguez, Jose Guadalupe Chacón-Nava and José Luis Reyes-Barragan

Metals 2025, 15(8), 899; https://doi.org/10.3390/met15080899 - 11 Aug 2025

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Abstract

This study investigates the effect of copper (Cu) and silver (Ag) additions on the electrochemical behavior of the Fe40Al intermetallic alloy in artificial saliva, aiming to evaluate its potential for biomedical applications such as dental implants. Alloys with varying concentrations of Ag (0.5, [...] Read more.

This study investigates the effect of copper (Cu) and silver (Ag) additions on the electrochemical behavior of the Fe40Al intermetallic alloy in artificial saliva, aiming to evaluate its potential for biomedical applications such as dental implants. Alloys with varying concentrations of Ag (0.5, 1.0, and 3.0 wt%) and Cu (1.0, 3.0, and 5.0 wt%) were synthesized and exposed to a biomimetic electrolyte simulating oral conditions. Electrochemical techniques, including open circuit potential (OCP), linear polarization resistance (LPR), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS), were employed to assess corrosion performance. Results show that unmodified Fe40Al exhibits good corrosion resistance, attributed to the formation of a stable passive oxide layer. The addition of Cu, particularly at 3.0 wt%, significantly improved corrosion resistance, yielding lower corrosion current densities and higher polarization resistance and charge transfer resistance values, surpassing even 316L stainless steel in some metrics. Conversely, Ag additions led to a degradation of corrosion resistance, especially at 3.0 wt%, due to microstructural changes and the formation of metallic Ag precipitates, AgSCN, and galvanic cells, which promoted localized corrosion. EIS results revealed that Cu- and Ag-modified alloys developed less homogeneous and less protective passive layers over time, as indicated by increased double-layer capacitance (C_dl) and reduced constant phase element exponent (n_dl) values. Overall, the Fe40Al alloy shows intrinsic corrosion resistance in simulated physiological environments, and Cu additions can enhance this performance under controlled conditions. However, Ag additions negatively affect the protective behavior of the passive layer. These findings offer critical insight into the design of Fe-Al-based biomaterials for dental or biomedical applications where corrosion resistance and electrochemical stability are paramount. Full article

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

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22 pages, 6453 KiB

Open AccessArticle

Experimental Study on the Microscale Milling Process of DD5 Nickel-Based Single-Crystal Superalloy

by Ying Li, Yadong Gong, Yang Liu, Zhiheng Wang, Junhe Zhao, Zhike Wang and Zelin Xu

Metals 2025, 15(8), 898; https://doi.org/10.3390/met15080898 - 11 Aug 2025

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Abstract

Technological advances have expanded the use of single-crystal in microscale applications—particularly in infrared optics, electronics, and aerospace. Conducting research on the surface quality of micro-milling processes for single-crystal superalloys has become a key factor in expanding their applications. In this paper, the nickel-based [...] Read more.

Technological advances have expanded the use of single-crystal in microscale applications—particularly in infrared optics, electronics, and aerospace. Conducting research on the surface quality of micro-milling processes for single-crystal superalloys has become a key factor in expanding their applications. In this paper, the nickel-based single-crystal superalloy DD5 is selected as the test object, and the finite element analysis software ABAQUS 2022 version is used to conduct a simulation study on its micro-scale milling process with reasonable milling parameters. A three-factor five-level L₂₅(5³) slot milling orthogonal experiment is conducted to investigate the effects of milling speed, milling depth, and feed rate on its milling force and surface quality, respectively. The results show that the milling depth has the greatest impact on the milling force during the micro-milling process, while the milling speed has the greatest influence on the surface quality. Finally, based on the experimental data, the optimal parameter combination for micro-milling nickel-based single-crystal superalloy DD5 parts is found—when the milling speed is 1318.8 mm/s; the milling depth is 12 µm; the feed rate is 20 µm/s; and the surface roughness value is at its minimum, indicating the best surface quality—which has certain guiding significance for practical machining. Full article

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34 pages, 22828 KiB

Open AccessArticle

Optimization of Process Parameters in Electron Beam Cold Hearth Melting and Casting of Ti-6wt%Al-4wt%V via CFD-ML Approach

by Yuchen Xin, Jianglu Liu, Yaming Shi, Zina Cheng, Yang Liu, Lei Gao, Huanhuan Zhang, Haohang Ji, Tianrui Han, Shenghui Guo, Shubiao Yin and Qiuni Zhao

Metals 2025, 15(8), 897; https://doi.org/10.3390/met15080897 - 11 Aug 2025

Viewed by 172

Abstract

During electron beam cold hearth melting (EBCHM) of Ti-6wt%Al-4wt%V titanium alloy, aluminum volatilization causes compositional segregation in the ingot, significantly degrading material performance. Traditional methods (e.g., the Langmuir equation) struggle to accurately predict aluminum diffusion and compensation behaviors, while computational fluid dynamics (CFD), [...] Read more.

During electron beam cold hearth melting (EBCHM) of Ti-6wt%Al-4wt%V titanium alloy, aluminum volatilization causes compositional segregation in the ingot, significantly degrading material performance. Traditional methods (e.g., the Langmuir equation) struggle to accurately predict aluminum diffusion and compensation behaviors, while computational fluid dynamics (CFD), although capable of resolving multiphysics fields in the molten pool, suffer from high computational costs and insufficient research on segregation control. To address these issues, this study proposes a CFD-machine learning (backpropagation neural network, CFD-ML(BP)) approach to achieve precise prediction and optimization of aluminum segregation. First, CFD simulations are performed to obtain the molten pool’s temperature field, flow field, and aluminum concentration distribution, with model reliability validated experimentally. Subsequently, a BP neural network is trained using large-scale CFD datasets to establish an aluminum concentration prediction model, capturing the nonlinear relationships between process parameters (e.g., casting speed, temperature) and compositional segregation. Finally, optimization algorithms are applied to determine optimal process parameters, which are validated via CFD multiphysics coupling simulations. The results demonstrate that this method predicts the average aluminum concentration in the ingot with an error of ≤3%, significantly reducing computational costs. It also elucidates the kinetic mechanisms of aluminum volatilization and diffusion, revealing that non-monotonic segregation trends arise from the dynamic balance of volatilization, diffusion, convection, and solidification. Moreover, the most uniform aluminum distribution (average 6.8 wt.%, R² = 0.002) is achieved in a double-overflow mold at a casting speed of 18 mm/min and a temperature of 2168 K. Full article

(This article belongs to the Special Issue Full-Cycle Innovation of Titanium Resources: From Mineral Development to High-End Material Manufacturing)

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21 pages, 8080 KiB

Open AccessArticle

Microstructural and Mechanical Characterization of Co-Free Al_xTi_xCrFe₂Ni High-Entropy Alloys

by Róbert Kočiško, Ondrej Milkovič, Patrik Petroušek, Gabriel Sučik, Dávid Csík, Karel Saksl, Ivan Petryshynets, Karol Kovaľ and Pavel Diko

Metals 2025, 15(8), 896; https://doi.org/10.3390/met15080896 - 10 Aug 2025

Viewed by 158

Abstract

This study investigates the effect of Al_x and Ti_x content (x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) on the microstructural evolution and mechanical properties of Co-free high-entropy Al_xTi_xCrFe₂Ni alloys in both as-cast and [...] Read more.

This study investigates the effect of Al_x and Ti_x content (x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) on the microstructural evolution and mechanical properties of Co-free high-entropy Al_xTi_xCrFe₂Ni alloys in both as-cast and homogenized conditions. The research focused on the characterization of structural features, melting behavior, and mechanical performance. Microstructural characterization was carried out using optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and differential thermal analysis (DTA). Mechanical properties were evaluated through Vickers hardness testing and uniaxial compression tests. Increasing the Al and Ti content induced a transformation from a single-phase FCC structure to a dual-phase BCC structure, with the primary BCC phase strengthened by spherical precipitates rich in Al, Ti, and Ni. Homogenization annealing at 1100 °C led to an overall improvement in the mechanical properties. The Al_0.3Ti_0.3CrFe₂Ni alloy exhibited the most balanced combination of strength and ductility after annealing, achieving a compressive yield strength of 1510 MPa, a compressive strength of 3316 MPa, and a compressive plastic strain of 45%. Full article

(This article belongs to the Special Issue Preparation, Properties, Microstructure and Applications of High Entropy Alloys)

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20 pages, 8934 KiB

Open AccessArticle

Numerical and Experimental Investigations on the Compressive Properties of the Graded BCC Lattice Cylindrical Shells Made of 316L Stainless Steel

by Yiting Guan, Wenjie Ma, Miao Cao, Hao Xu, Wenchang Luo, Weidong Cao, Siying Wang, Ying Qin, Xiaoyu Zhang and Xiaofei Cao

Metals 2025, 15(8), 895; https://doi.org/10.3390/met15080895 - 10 Aug 2025

Viewed by 228

Abstract

Uniform and graded BCC lattice cylindrical shells were proposed, and the corresponding structural specimens were fabricated with 316L stainless steel material. Experimental testing and numerical simulations were both utilized to investigate the quasi-static and dynamic compression behavior of the uniform and graded BCC [...] Read more.

Uniform and graded BCC lattice cylindrical shells were proposed, and the corresponding structural specimens were fabricated with 316L stainless steel material. Experimental testing and numerical simulations were both utilized to investigate the quasi-static and dynamic compression behavior of the uniform and graded BCC lattice cylindrical shells. Finite element results were compared with the experimental results. Parametric studies were conducted to study the effects of relative density, gradient distribution, and loading velocity on the mechanical properties and deformation features. When the relative density increased from 9% to 25%, a 175% increase in SEA could be seen. Graded BCC lattice cylindrical shells almost exhibited the same mechanical performance. When compared with the SEA value under low-speed loading conditions, a 26.95% maximum increase could be witnessed in the graded-5 specimen under high-speed loading. Testing results indicated that the proposed uniform and graded BCC lattice cylindrical shells exhibited fascinating quasi-static and dynamic mechanical behavior, which provided guidance for the design and application of next-generation lightweight materials with excellent protective properties. Full article

(This article belongs to the Special Issue Additive Manufactured Metal Structural Materials)

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18 pages, 4208 KiB

Open AccessArticle

Experimental Study and Defect Control in Picosecond Laser Trepanning Drilling of Superalloy

by Liang Wang, Yefei Rong, Long Xu, Changjian Wu and Kaibo Xia

Metals 2025, 15(8), 893; https://doi.org/10.3390/met15080893 - 10 Aug 2025

Viewed by 151

Abstract

Picosecond laser trepanning is a key technology for fabricating film cooling holes in aero-engine turbine blades, overcoming the limitations of conventional machining such as severe tool wear and thermal damage. However, optimizing this advanced process to achieve consistent, high-quality results remains a challenge. [...] Read more.

Picosecond laser trepanning is a key technology for fabricating film cooling holes in aero-engine turbine blades, overcoming the limitations of conventional machining such as severe tool wear and thermal damage. However, optimizing this advanced process to achieve consistent, high-quality results remains a challenge. This study therefore systematically investigates the influence of key laser parameters (power, scanning speed, defocusing distance, and number of scans) on the geometric quality (diameter, taper, and roundness) of holes trepanned in GH4169 superalloy. The experimental results revealed that laser power and defocusing distance are the dominant factors controlling hole diameter and taper. Furthermore, a critical trade-off was identified concerning the number of scans: while more scans improved exit roundness, they also detrimentally increased entrance diameter and taper due to heat accumulation. Based on these findings, we propose a defect control strategy prioritizing a lower number of scans in the initial phase to effectively suppress molten material formation and preserve surface integrity. This work provides a valuable technological reference and theoretical foundation for the low-damage, high-reliability laser manufacturing of high-performance aerospace components. Full article

(This article belongs to the Special Issue Advances in Laser Processing of Metals and Alloys)

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19 pages, 437 KiB

Open AccessArticle

Combined Influence of Stretch-Bending Straightening and Ageing on the Tensile Properties of Packaging Steels

by Sebastian Möller, Dimitrios Nouskalis, Björn Ehmke, Holm Altenbach and Christian Dresbach

Metals 2025, 15(8), 894; https://doi.org/10.3390/met15080894 - 9 Aug 2025

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Abstract

Stretch-bending straightening is used to ensure the desired flatness properties of packaging steel in the final stage of semi-finished product manufacturing. Not only is the flatness of the steel affected by the alternating bending load and the tensile load during the stretch-bending straightening [...] Read more.

Stretch-bending straightening is used to ensure the desired flatness properties of packaging steel in the final stage of semi-finished product manufacturing. Not only is the flatness of the steel affected by the alternating bending load and the tensile load during the stretch-bending straightening process, but the mechanical properties also change depending on several factors. It was found out that the stretch-bending straightening parameters, the temper-rolling degree and the amount of interstitial elements have an influence on this change in mechanical properties. A follow-up ageing process, after stretch-bending straightening, also has a significant impact on this change. Based on these observations, a multivariate prediction model is developed describing the dependence between straightening parameters and resulting yield strength characteristics in non-aged and aged conditions for three different packaging steels. Full article

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18 pages, 5965 KiB

Open AccessArticle

Al₂O₃-Embedded LiNi_0.9Mn_0.05Al_0.05O₂ Cathode Engineering for Enhanced Cyclic Stability in Lithium-Ion Batteries

by Fei Liu, Chenfeng Wang, Ning Yang, Zundong Xiao, Aoxuan Wang and Rijie Wang

Metals 2025, 15(8), 892; https://doi.org/10.3390/met15080892 - 8 Aug 2025

Viewed by 268

Abstract

With the rapid advancement of new energy electric vehicles, high-capacity nickel-rich layered oxides have emerged as predominant cathode materials in lithium-ion battery systems. However, their widespread implementation necessitates rigorous investigation into cycling stability. We synthesized nickel-manganese-aluminum hydroxide precursors as raw materials by co-precipitation [...] Read more.

With the rapid advancement of new energy electric vehicles, high-capacity nickel-rich layered oxides have emerged as predominant cathode materials in lithium-ion battery systems. However, their widespread implementation necessitates rigorous investigation into cycling stability. We synthesized nickel-manganese-aluminum hydroxide precursors as raw materials by co-precipitation method, and synthesized ultrathin Al₂O₃-coated LiNi_0.9Mn_0.05Al_0.05O₂ cathode materials by hydrolysis reaction. The cathode material was uniformly covered by an Al₂O₃ layer with an average thickness of 5–10 nm by high resolution transmission electron microscopy (HRTEM). Electrochemical performance tests showed that the modified cathode material exhibited significantly enhanced reversible capacity, cycling stability, and rate performance, and a more favorable differential capacity curve. In particular, the LNMA-2 samples were able to maintain 90.6% and 88.3% of their initial capacity after 100 cycle tests (with cutoff voltages of 4.3 and 4.5 V, respectively) at 0.5 C charge/discharge rate. These improved electrochemical properties are mainly attributed to the advantages offered by the unique Al₂O₃ coating structure. This study provides significant theoretical value for designing and optimizing the production of high-nickel cobalt-free cathode materials with high cycling performance. Full article

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18 pages, 3886 KiB

Open AccessArticle

Bio-Desilication of Coal Fly Ash and the Impacts on Critical Metal Recovery

by Shulan Shi, Ting Chen, Simeng Ren and Jinhe Pan

Metals 2025, 15(8), 891; https://doi.org/10.3390/met15080891 - 8 Aug 2025

Viewed by 199

Abstract

Critical metals such as rare earth elements (REEs) are primarily associated with silicates and aluminosilicates in coal fly ash, resulting in poor REE recovery. Silicate bacteria can decompose silicate minerals and release silicon, but their impact on REE extraction remains unclear. In this [...] Read more.

Critical metals such as rare earth elements (REEs) are primarily associated with silicates and aluminosilicates in coal fly ash, resulting in poor REE recovery. Silicate bacteria can decompose silicate minerals and release silicon, but their impact on REE extraction remains unclear. In this study, two coal fly ash samples with different origins and combustion methods were bioleached by Paenibacillus mucilaginosus, and the effects of bio-desilication on REE leaching were examined. First, the optimal bio-desilication conditions were determined as a pulp density of 1%, an initial pH of 7.0 and an initial cell concentration OD₆₀₀ = 0.2. Compared to circulating fluidized bed (CFB) coal fly ash, silicon in pulverized coal furnace (PCF) coal fly ash was more difficult to dissolve by P. mucilaginosus. After bio-desilication, the acid leaching rate of REEs improved by 8–15% for CFB coal fly ash but only 4–5% for the PCF sample. Further investigation found that the surface turned rough and the specific surface area of coal fly ash increased after bio-desilication, which are conducive to REE extraction. Additionally, there was more quartz and mullite in PCF coal fly ash, which are more resistant to biological corrosion than amorphous silicate. The results demonstrate that bio-desilication can improve REE recovery, providing new perspectives for the low-cost green utilization of coal fly ash. Full article

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23 pages, 7586 KiB

Open AccessArticle

Multi-Scale Mechanical Anisotropy and Heat Treatment Effects in Additively Manufactured AlSi10Mg

by Aikaterini Argyrou, Leonidas Gargalis, Leonidas Karavias, Evangelia K. Karaxi and Elias P. Koumoulos

Metals 2025, 15(8), 890; https://doi.org/10.3390/met15080890 - 8 Aug 2025

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Abstract

This study investigates the combined effects of build planes and heat treatments on the micro- and nanoscale mechanical properties of additively manufactured AlSi10Mg alloy. The hardness and elastic modulus were examined across two principal planes, XY and XZ, under three conditions: as-built (AB), [...] Read more.

This study investigates the combined effects of build planes and heat treatments on the micro- and nanoscale mechanical properties of additively manufactured AlSi10Mg alloy. The hardness and elastic modulus were examined across two principal planes, XY and XZ, under three conditions: as-built (AB), after solution annealing followed by water quenching (SA), and artificially aged after solution annealing (SA&AA). The results reveal that hardness is significantly affected by heat treatment, decreasing after SA and partially recovering upon subsequent artificial aging (SA&AA), while remaining largely unaffected by build planes, with average values differing by less than 2%. In contrast, the elastic modulus demonstrates a clear anisotropy, correlated with the microstructural changes from both additive manufacturing and thermal post-processing. The XY plane initially shows a modulus up to 29% higher than the XZ plane. However, after aging, the values of both planes converge to similar levels. While average values suggest general trends, localized measurements reveal notable spatial heterogeneity in both the hardness and elastic modulus—particularly after thermal treatments—arising from microstructural evolutions. These findings highlight the complex interplay between orientation and thermal history, underscoring that the mechanical performance of AlSi10Mg is governed by the synergistic effects that influence anisotropy and local mechanical behavior. Full article

(This article belongs to the Special Issue Welding and Additive Manufacturing of Metals)

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16 pages, 5615 KiB

Open AccessArticle

Surface Integrity Evolution and Fretting Wear Improvement of DD6 Single-Crystal Superalloy via Laser Shock Peening and Laser Shock Peening Without Coating

by Yuliang Li, Linjie Qiao, Xiaofeng Dang, Mo Lang, Sihai Luo, Liucheng Zhou, Xiaoqing Liang and Weifeng He

Metals 2025, 15(8), 889; https://doi.org/10.3390/met15080889 - 8 Aug 2025

Viewed by 217

Abstract

In this paper, the different effects of laser shock peening (LSP) and laser shock peening without coating (LSPwC) on the morphology, microhardness and fretting-wear behavior of DD6 Ni-based single-crystal superalloy are investigated. The results show that the surface roughness of DD6 decreases slightly [...] Read more.

In this paper, the different effects of laser shock peening (LSP) and laser shock peening without coating (LSPwC) on the morphology, microhardness and fretting-wear behavior of DD6 Ni-based single-crystal superalloy are investigated. The results show that the surface roughness of DD6 decreases slightly after LSP, while it increases after LSPwC due to surface remelting. Shock wave strengthening during LSP and LSPwC results in plastic deformation of the surface layer of DD6 samples. However, besides work hardening from shock wave, dispersion strengthening of oxide particles also occurs during LSPwC. Therefore, after LSPwC, the microhardness of the DD6 surface layer increases by 38.8%, higher than the increase of 27.7% after LSP. The fretting wear resistance of DD6 increases by about 42.8% and 58% after LSP and LSPwC, respectively. The surface roughness only affects the friction coefficient at the initial stage of fretting wear. The hardness increase caused by work hardening and the dispersion strengthening of surface oxides after laser strengthening is the key to the improvement of fretting wear resistance. The main wear mechanisms of untreated and LSP sample are oxidation wear, abrasive wear and adhesive wear, while the main wear mechanisms of LSPwC sample are oxidation wear and adhesive wear. Full article

(This article belongs to the Section Structural Integrity of Metals)

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16 pages, 3493 KiB

Open AccessArticle

Harnessing Industrial Waste for Sustainable Arsenic in a Mine Leachate Treatment

by Begoña Fernández, Julia Ayala and Rafael Rodríguez

Metals 2025, 15(8), 888; https://doi.org/10.3390/met15080888 - 8 Aug 2025

Viewed by 236

Abstract

This study focuses on the removal of arsenic (As) from contaminated water originating from an abandoned mercury mine landfill. To obtain results that more accurately reflect the material’s behavior under real-world conditions, tests were conducted starting with agitation, followed by column tests, and [...] Read more.

This study focuses on the removal of arsenic (As) from contaminated water originating from an abandoned mercury mine landfill. To obtain results that more accurately reflect the material’s behavior under real-world conditions, tests were conducted starting with agitation, followed by column tests, and subsequently channel tests. The results demonstrated high efficacy of industrial waste materials (FA, HA, and EA) in adsorbing As, with a significant reduction of this contaminant in the leachates. Practical applications of this methodology include its potential use in large-scale remediation projects, improving water quality in mining-affected areas, and contributing to sustainable waste management practices. Full article

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24 pages, 7185 KiB

Open AccessArticle

Hot Extrusion Process Grain Size Prediction and Effects of Friction Models and Hydraulic Press Applications

by Mohd Kaswandee Razali, Yun Heo and Man Soo Joun

Metals 2025, 15(8), 887; https://doi.org/10.3390/met15080887 - 7 Aug 2025

Viewed by 134

Abstract

This study focuses on realistic modeling of forming load and microstructural evolution during hot metal extrusion, emphasizing the effects of friction models and hydraulic press behavior. Rather than merely predicting load magnitudes, the objective is to replicate actual press operation by integrating a [...] Read more.

This study focuses on realistic modeling of forming load and microstructural evolution during hot metal extrusion, emphasizing the effects of friction models and hydraulic press behavior. Rather than merely predicting load magnitudes, the objective is to replicate actual press operation by integrating a load limit response into finite element modeling (FEM). By applying Coulomb and shear friction models under both constant and hydraulically controlled press conditions, the resulting impact on grain size evolution during deformation is examined. The hydraulic press simulation features a maximum load threshold that dynamically reduces die velocity once the limit is reached, unlike constant presses that sustain velocity regardless of load. P91 steel is used as the material system, and the predicted grain size is validated against experimentally measured data. Incorporating hydraulic control into FEM improves the representativeness of simulation results for industrial-scale extrusion, enhancing microstructural prediction accuracy, and ensuring forming process reliability. Full article

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39 pages, 5853 KiB

Open AccessArticle

Development of Technology for Processing Pyrite–Cobalt Concentrates to Obtain Pigments of the Composition Fe₂O₃ and Fe₃O₄

by Tatyana Chepushtanova, Aliya Altmyshbayeva, Yerik Merkibayev, Kulzira Mamyrbayeva, Zhanat Yespenova and Brajendra Mishra

Metals 2025, 15(8), 886; https://doi.org/10.3390/met15080886 - 7 Aug 2025

Viewed by 136

Abstract

This paper presents the results of a study on the development of a processing technology for pyrite–cobalt concentrates to obtain iron oxide pigments (Fe₂O₃ and Fe₃O₄) via high-temperature hydrolysis. It was found that, in a single [...] Read more.

This paper presents the results of a study on the development of a processing technology for pyrite–cobalt concentrates to obtain iron oxide pigments (Fe₂O₃ and Fe₃O₄) via high-temperature hydrolysis. It was found that, in a single operation, the concentrate can be effectively purified from lead, zinc, and copper, yielding an iron–nickel–cobalt product suitable for further processing by standard technologies, such as smelting into ferronickel. The scientific originality of research concludes in a mechanism of stepwise selective chloride volatilization, which was established as follows: stage I (500–650 °C)—removal of lead; stage II (700–750 °C)—chlorination of copper and iron; stage III (850–900 °C)—volatilization of nickel and cobalt. Microprobe analysis of the powders obtained from high-temperature hydrolysis of FeCl₂·4H₂O and FeCl₃·6H₂O revealed the resulting Fe₃O₄ and Fe₂O₃ powders with particle sizes 50 μm and 100 μm. A visual color palette was created, corresponding to different Fe₃O₄/Fe₂O₃ ratios in the pigment composition—ranging from black (magnetite) to red (hematite)—and potential application areas. For the first time, the new technological scheme was proposed of pigments Fe₂O₃ and Fe₃O₄ production from pyrite–cobalt concentrates via combination of oxidized roasting with subsequent chlorination and high-temperature hydrolysis of the products. Full article

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17 pages, 5080 KiB

Open AccessArticle

Effect of External Constraints on Deformation Behavior of Aluminum Single Crystals Cold-Rolled to High Reduction: Crystal Plasticity FEM Study and Experimental Verification

by Hui Wang, Junyao Dong, Shunjie Yao, Shuqi Liu, Letian Cao and Xi Huang

Metals 2025, 15(8), 885; https://doi.org/10.3390/met15080885 - 7 Aug 2025

Viewed by 198

Abstract

In this study, aluminum single crystals with a {1 0 0} <0 0 1> (Cube) orientation were rolled under two conditions: with external constraints imposed by an external aluminum frame (3DRC) and without external constraints (3DR). The crystal plasticity finite element method (CPFEM) [...] Read more.

In this study, aluminum single crystals with a {1 0 0} <0 0 1> (Cube) orientation were rolled under two conditions: with external constraints imposed by an external aluminum frame (3DRC) and without external constraints (3DR). The crystal plasticity finite element method (CPFEM) was used to simulate texture evolution, and the results corresponded well with experimental observations. The minor discrepancies observed were primarily attributed to the idealized conditions in the simulation. The results demonstrate that in the 3DR model, crystal orientations predominantly rotate around the transverse direction (TD), with non-TD rotations playing a secondary role. In contrast, the 3DRC model exhibits similar rotation patterns to 3DR at lower reductions, but at higher reductions, non-TD rotations become comparable to TD rotations. This difference results in more concentrated orientations in 3DR and more dispersed orientations in 3DRC. Additionally, analysis reveals that external constraints cause deformation behavior to deviate from the plane strain condition rather than move closer to it. The presence of external constraints alters stress and strain states, modifying the activation of slip systems and crystal rotations, leading to significant variations in slip activity, shear strain, and crystal rotation along TD. Full article

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14 pages, 3669 KiB

Open AccessArticle

Facile Approach for Fabrication of Hydrophobic Aluminum Alloy Surfaces Using Fatty Acids

by Alina Matei, Oana Brincoveanu and Vasilica Ţucureanu

Metals 2025, 15(8), 884; https://doi.org/10.3390/met15080884 - 7 Aug 2025

Viewed by 204

Abstract

Alloys and metals exhibit high sensitivity to corrosion and aggressive environments. Hence, the development of protective treatments through accessible methods with a high degree of protection has become a necessity. This paper presents a method for treating the hydrophilic surface of aluminum alloys [...] Read more.

Alloys and metals exhibit high sensitivity to corrosion and aggressive environments. Hence, the development of protective treatments through accessible methods with a high degree of protection has become a necessity. This paper presents a method for treating the hydrophilic surface of aluminum alloys using two types of unsaturated fatty acids, thereby increasing the degree of hydrophobicity and protecting the material. The samples were cleaned by a chemical process, followed by immersion in oleic acid (C₁₈H₃₄O₂, 18:1 cis-9) and elaidic acid (C₁₈H₃₄O₂, 18:1 trans-9), and they were then treated at a temperature of 80 °C. Morphological and microstructural analyses were conducted using OM, FE-SEM, EDX, and FTIR to understand the influence of unsaturated monocarboxylic fatty acids on the alloy surfaces. The wettability capacity of the alloys was investigated by measuring the contact angle (CA). The results revealed that the cleaning step and modification treatment with fatty acids are essential steps for increasing the hydrophobic character of the surface. This study can be applied to various types of metallic substrates to enhance their corrosion resistance and long-term chemical stability in aggressive environments, making it adaptable for use in different industrial fields. Full article

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

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24 pages, 6501 KiB

Open AccessArticle

Exploring Lattice Rotations Induced by Kinematic Constraints in Deep Drawing from Crystal Plasticity Approach

by Yu-Xuan Jiang, Shih-Heng Tung and Jui-Chao Kuo

Metals 2025, 15(8), 883; https://doi.org/10.3390/met15080883 - 7 Aug 2025

Viewed by 179

Abstract

The anisotropic nature of cup ears formed during the deep drawing of sheet metals is governed by the distribution of crystallographic orientation in interaction between earing. In this study, we examined the orientation development of a cube-oriented aluminum single crystal to couple the [...] Read more.

The anisotropic nature of cup ears formed during the deep drawing of sheet metals is governed by the distribution of crystallographic orientation in interaction between earing. In this study, we examined the orientation development of a cube-oriented aluminum single crystal to couple the deep drawing kinematics with the formation of anisotropic orientations. A quarter model of a circular deep-drawn blank was simulated in the finite element software using a user-defined material subroutine. A cube-oriented aluminum single crystal was designed to serve as a reference and trace the orientation evolution in the deep drawing process. After the deep drawing, the bottom, wall, and flange of the drawn cup were investigated at azimuthal angles (

α

) of 0° and 45° with respect to the radial direction (RD) in terms of the orientation. Our findings show that the change in the lattice orientation could be attributed to the rotation induced by drawing and bending processes under kinematic constraints. Thus, the initial cube orientation developed into different orientations during the deep drawing. The type-A slip system mainly contributed to the radial strain at α = 0°, and type-B and C slip systems accounted for the longitudinal and circumferential strains at α = 45°. Full article

(This article belongs to the Special Issue Feature Papers in Crystallography and Applications of Metallic Materials (2nd Edition))

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5 pages, 142 KiB

Open AccessEditorial

Manufacturing and Characterization of Metallic Electrode Materials

by Que Huang

Metals 2025, 15(8), 882; https://doi.org/10.3390/met15080882 - 7 Aug 2025

Viewed by 112

Abstract

In recent years, the growing demand for resources has driven the development of energy storage devices and related technologies, particularly the application of metal electrode materials, which are of particular importance in lithium, sodium, potassium, and zinc-based ion batteries, metal batteries, and solar [...] Read more.

In recent years, the growing demand for resources has driven the development of energy storage devices and related technologies, particularly the application of metal electrode materials, which are of particular importance in lithium, sodium, potassium, and zinc-based ion batteries, metal batteries, and solar energy storage and catalytic technologies [...] Full article

(This article belongs to the Special Issue Manufacturing and Characterization of Metallic Electrode Materials)

26 pages, 11995 KiB

Open AccessArticle

Research on Hydrogen/Deuterium Permeation Behavior and Influencing Factors of X52MS Pipeline Steel

by Ning Liu, Ke Jin, Junqiang Ren, Jie Sheng, Xuefeng Lu and Xingchang Tang

Metals 2025, 15(8), 881; https://doi.org/10.3390/met15080881 - 7 Aug 2025

Viewed by 245

Abstract

The hydrogen/deuterium permeation behavior of X52MS pipeline steel with three thicknesses was investigated using the gas/liquid phase permeation method by changing the current density and regulating the surface roughness. The permeation curves under different conditions were obtained, the hydrogen/deuterium diffusion coefficients and related [...] Read more.

The hydrogen/deuterium permeation behavior of X52MS pipeline steel with three thicknesses was investigated using the gas/liquid phase permeation method by changing the current density and regulating the surface roughness. The permeation curves under different conditions were obtained, the hydrogen/deuterium diffusion coefficients and related important parameters were calculated, and the surface morphology of the hydrogen-filled side was observed using scanning electron microscopy. It is found that the hydrogen diffusion coefficient and diffusion flux increase gradually with an increase in the hydrogen charging current density, while the hydrogen infiltration lag time gradually decreases. With the increase in surface roughness of the specimen, the corrosion degree of the surface after hydrogen penetration decreases, the hydrogen diffusion coefficient gradually decreases, and the penetration time, lag time, and hydrogen concentration on the cathode side gradually increase. Full article

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20 pages, 4891 KiB

Open AccessArticle

Electrochemical Behavior of Thermomechanically Processed UNS S41003 Steel in Acidic Chloride Media: Assessing Martensitic Transformation Effects

by Carlos H. B. Queiroz, Davi A. Marques, Otílio B. F. Diógenes, Daniel de C. Girão, Roberta B. Vasques, Adolfo K. do N. Viana, Gemma Fargas, Mauro A. C. Florez and Walney S. Araújo

Metals 2025, 15(8), 880; https://doi.org/10.3390/met15080880 - 7 Aug 2025

Viewed by 266

Abstract

UNS S41003 is a low-cost, low-carbon ferritic stainless steel that exhibits moderate corrosion resistance but limited mechanical performance. This study evaluates the electrochemical behavior of untreated and thermomechanically treated UNS S41003 samples. Corrosion tests were conducted in acidic electrolytes with varying pH to [...] Read more.

UNS S41003 is a low-cost, low-carbon ferritic stainless steel that exhibits moderate corrosion resistance but limited mechanical performance. This study evaluates the electrochemical behavior of untreated and thermomechanically treated UNS S41003 samples. Corrosion tests were conducted in acidic electrolytes with varying pH to simulate aggressive environments relevant to industrial and structural applications where exposure to acidic media and corrosive pollutants occurs. Potentiodynamic polarization curves for all samples displayed passive regions typically associated with protective oxide film formation; however, localized pitting corrosion was detected post-test. Electrochemical impedance spectroscopy indicated a marked decrease in corrosion resistance as pH decreased. The corrosion resistance of the treated alloy remained comparable to that of the untreated condition, indicating that thermomechanical processing did not detrimentally affect passivity or corrosion performance under the tested conditions. The literature suggests that the applied treatment enhances mechanical properties, supporting the potential use of this alloy in structural components subjected to acidic environments requiring a balance of mechanical strength and corrosion resistance. Full article

(This article belongs to the Special Issue Corrosion Behavior of Alloys in Water Environments)

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33 pages, 7351 KiB

Open AccessArticle

Constructal Design and Numerical Simulation Applied to Geometric Evaluation of Stiffened Steel Plates Subjected to Elasto-Plastic Buckling Under Biaxial Compressive Loading

by Andrei Ferreira Lançanova, Raí Lima Vieira, Elizaldo Domingues dos Santos, Luiz Alberto Oliveira Rocha, Thiago da Silveira, João Paulo Silva Lima, Emanuel da Silva Diaz Estrada and Liércio André Isoldi

Metals 2025, 15(8), 879; https://doi.org/10.3390/met15080879 - 6 Aug 2025

Viewed by 248

Abstract

Widely employed in diverse engineering applications, stiffened steel plates are often subjected to biaxial compressive loads. Under these conditions, buckling may occur, initially within the elastic range but potentially progressing into the elasto-plastic domain, which can lead to permanent deformations or structural collapse. [...] Read more.

Widely employed in diverse engineering applications, stiffened steel plates are often subjected to biaxial compressive loads. Under these conditions, buckling may occur, initially within the elastic range but potentially progressing into the elasto-plastic domain, which can lead to permanent deformations or structural collapse. To increase the ultimate buckling stress of plates, the implementation of longitudinal and transverse stiffeners is effective; however, this complexity makes analytical stress calculations challenging. As a result, numerical methods like the Finite Element Method (FEM) are attractive alternatives. In this study, the Constructal Design method and the Exhaustive Search technique were employed and associated with the FEM to optimize the geometric configuration of stiffened plates. A steel plate without stiffeners was considered, and 30% of its volume was redistributed into stiffeners, creating multiple configuration scenarios. The objective was to investigate how different arrangements and geometries of stiffeners affect the ultimate buckling stress under biaxial compressive loading. Among the configurations evaluated, the optimal design featured four longitudinal and two transverse stiffeners, with a height-to-thickness ratio of 4.80. This configuration significantly improved the performance, achieving an ultimate buckling stress 472% higher than the unstiffened reference plate. In contrast, the worst stiffened configuration led to a 57% reduction in performance, showing that not all stiffening strategies are beneficial. These results demonstrate that geometric optimization of stiffeners can significantly enhance the structural performance of steel plates under biaxial compression, even without increasing material usage. The approach also revealed that intermediate slenderness values lead to better stress distribution and delayed local buckling. Therefore, the methodology adopted in this work provides a practical and effective tool for the design of more efficient stiffened plates. Full article

(This article belongs to the Special Issue Advanced Plastic Forming Processes: Theory, Experiments and Numerical Simulations)

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15 pages, 1952 KiB

Open AccessArticle

Processing of Secondary Raw Materials from Ferrochrome Production via Agglomeration and Study of Their Mechanical Properties

by Yerlan Zhumagaliyev, Yerbol Shabanov, Maral Almagambetov, Maulen Jundibayev, Nursultan Ulmaganbetov, Salamat Laikhan, Akgul Jundibayeva, Aigerim Abilberikova, Nurbala Ubaidulayeva and Rysgul Adaibayeva

Metals 2025, 15(8), 878; https://doi.org/10.3390/met15080878 - 6 Aug 2025

Viewed by 228

Abstract

In the process of producing ferroalloys, a large amount of secondary raw materials is formed, including slag, aspiration dusts and sludge. The recycling of secondary raw materials can create resources and bring environmental and economic benefits. Wet secondary raw materials (WSRMs) are characterized [...] Read more.

In the process of producing ferroalloys, a large amount of secondary raw materials is formed, including slag, aspiration dusts and sludge. The recycling of secondary raw materials can create resources and bring environmental and economic benefits. Wet secondary raw materials (WSRMs) are characterized by a high chromium oxide content (averaging 24%), but due to their high moisture levels, they cannot be directly used in arc furnaces. As a strategic approach, mixing WSRMs with drier, more chromium-rich dusts (up to 45% Cr₂O₃) has been proposed. This not only reduces the overall moisture content of the mixture but also enhances the metallurgical value of the charge material. This paper presents the results of laboratory studies on the agglomeration of secondary wet raw materials using briquetting, extrusion and pelletizing methods. The main factors influencing the quality of the resulting product were analyzed, including the method of agglomeration, the composition of the mixture, as well as the type and dosage of the binder component. The strength characteristics of the finished agglomerated samples were evaluated in terms of resistance to splitting, impact loads and falling. Notably, the selected binders are organic and polymer substances capable of complete combustion under metallurgical smelting conditions. Full article

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22 pages, 25395 KiB

Open AccessArticle

Hot Deformation and Predictive Modelling of β-Ti-15Mo Alloy: Linking Flow Stress, ω-Phase Evolution, and Thermomechanical Behaviour

by Arthur de Bribean Guerra, Alberto Moreira Jorge Junior, Guilherme Yuuki Koga and Claudemiro Bolfarini

Metals 2025, 15(8), 877; https://doi.org/10.3390/met15080877 - 6 Aug 2025

Viewed by 211

Abstract

This study investigates the hot deformation behaviour and flow stress prediction of metastable β-Ti-15Mo alloy, a promising material for biomedical applications requiring strength–modulus optimisation and thermomechanical tunability. Isothermal compression tests were performed within the temperature range of 923–1173 K and at strain rates [...] Read more.

This study investigates the hot deformation behaviour and flow stress prediction of metastable β-Ti-15Mo alloy, a promising material for biomedical applications requiring strength–modulus optimisation and thermomechanical tunability. Isothermal compression tests were performed within the temperature range of 923–1173 K and at strain rates of 0.17, 1.72, and 17.2

s^{- 1}

to assess the material’s response under industrially relevant hot working conditions. The alloy showed significant sensitivity to temperature and strain rate, with dynamic recovery (DRV) and dynamic recrystallisation (DRX) dominating the softening behaviour depending on the conditions. A strain-compensated Arrhenius-type constitutive model was developed and validated, resulting in an apparent activation energy of approximately 234 kJ/mol. Zener–Hollomon parameter analysis confirmed a transition in deformation mechanisms. Although microstructural and diffraction data suggest possible contributions from nanoscale phase transformations, including ω-phase dissolution at high temperatures, these aspects remain to be fully elucidated. The model offers reliable predictions of flow behaviour and supports optimisation of thermomechanical processing routes for biomedical β-Ti alloys. Full article

(This article belongs to the Special Issue Hot Forming/Processing of Metals and Alloys)

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20 pages, 772 KiB

Open AccessReview

Treatment of Refractory Oxidized Nickel Ores (ONOs) from the Shevchenkovskoye Ore Deposit

by Chingis A. Tauakelov, Berik S. Rakhimbayev, Aliya Yskak, Khusain Kh. Valiev, Yerbulat A. Tastanov, Marat K. Ibrayev, Alexander G. Bulaev, Sevara A. Daribayeva, Karina A. Kazbekova and Aidos A. Joldassov

Metals 2025, 15(8), 876; https://doi.org/10.3390/met15080876 - 6 Aug 2025

Viewed by 286

Abstract

The increasing depletion of high-grade nickel sulfide deposits and the growing demand for nickel have intensified global interest in oxidized nickel ores (ONOs), particularly those located in Kazakhstan. This study presents a comprehensive review of the mineralogical and chemical characteristics of ONOs from [...] Read more.

The increasing depletion of high-grade nickel sulfide deposits and the growing demand for nickel have intensified global interest in oxidized nickel ores (ONOs), particularly those located in Kazakhstan. This study presents a comprehensive review of the mineralogical and chemical characteristics of ONOs from the Shevchenkovskoye cobalt–nickel ore deposit and other Kazakhstan deposits, highlighting the challenges they pose for conventional beneficiation and metallurgical processing. Current industrial practices are analyzed, including pyrometallurgical, hydrometallurgical, and pyro-hydrometallurgical methods, with an emphasis on their efficiency, environmental impact, and economic feasibility. Special attention is given to the potential of hydro-catalytic leaching as a flexible, energy-efficient alternative for treating low-grade ONOs under atmospheric conditions. The results underscore the necessity of developing cost-effective and sustainable technologies tailored to the unique composition of Kazakhstani ONOs, particularly those rich in iron and magnesium. This work provides a strategic framework for future research and the industrial application of advanced leaching techniques to unlock the full potential of Kazakhstan’s nickel resources. Full article

(This article belongs to the Section Extractive Metallurgy)

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