Metals

30 pages, 65330 KiB

Open AccessArticle

Experiments and Simulations on the Low-Temperature Reduction of Iron Ore Oxide Pellets with Hydrogen

by Róbert Findorák, Zuzana Miškovičová, Jaroslav Legemza, Róbert Dzurňák, Branislav Buľko, Peter Demeter, Andrea Egryová and Róbert Maliňák

Metals 2025, 15(3), 289; https://doi.org/10.3390/met15030289 - 6 Mar 2025

Abstract

This article examines the low-temperature reducibility of four types of iron ore pellets in a pure hydrogen atmosphere, with the aim of understanding the thermodynamic aspects of the process. The research focuses on optimizing conditions for pellet reduction in order to reduce CO [...] Read more.

This article examines the low-temperature reducibility of four types of iron ore pellets in a pure hydrogen atmosphere, with the aim of understanding the thermodynamic aspects of the process. The research focuses on optimizing conditions for pellet reduction in order to reduce CO₂ emissions and improve iron production efficiency. Experimental tests were conducted at temperatures of 600 °C and 800 °C, supplemented by thermodynamic simulations predicting the equilibrium composition and energy requirements. Chemical and microstructural analyses revealed that porosity, mineralogical composition, and phase distribution homogeneity significantly affect reduction efficiency. High-quality pellets with low SiO₂ content demonstrated the best reduction ability, while fluxed pellets with the presence of calcium silicate ferrites and pellets with a higher content of SiO₂ showed lower reduction potential due to the presence of hard-to-reduce phases such as calcium silicate ferrites and iron silicates. The results highlight the importance of controlling process conditions and optimizing pellet properties to enhance the reduction process and minimize environmental impacts. This study provides valuable insights for the application of hydrogen reduction in industrial conditions, contributing to the decarbonization of the metallurgical industry. Full article

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15 pages, 3466 KiB

Open AccessArticle

Prediction of Creep Rupture Life of 5Cr-0.5Mo Steel Using Machine Learning Models

by Muhammad Ishtiaq, Hafiz Muhammad Rehan Tariq, Devarapalli Yuva Charan Reddy, Sung-Gyu Kang and Nagireddy Gari Subba Reddy

Metals 2025, 15(3), 288; https://doi.org/10.3390/met15030288 - 6 Mar 2025

Abstract

The creep rupture life of 5Cr-0.5Mo steels used in high-temperature applications is significantly influenced by factors such as minor alloying elements, hardness, austenite grain size, non-metallic inclusions, service temperature, and applied stress. The relationship of these variables with the creep rupture life is [...] Read more.

The creep rupture life of 5Cr-0.5Mo steels used in high-temperature applications is significantly influenced by factors such as minor alloying elements, hardness, austenite grain size, non-metallic inclusions, service temperature, and applied stress. The relationship of these variables with the creep rupture life is quite complex. In this study, the creep rupture life of 5Cr-0.5Mo steel was predicted using various machine learning (ML) models. To achieve higher accuracy, various ML techniques, including random forest (RF), gradient boosting (GB), linear regression (LR), artificial neural network (ANN), AdaBoost (AB), and extreme gradient boosting (XGB), were applied with careful optimization of hidden parameters. Among these, the ANN-based model demonstrated superior performance, yielding high accuracy with minimal prediction errors for the test dataset (RMSE = 0.069, MAE = 0.053, MAPE = 0.014, and R² = 1). Additionally, we developed a user-friendly graphical user interface (GUI) for the ANN model, enabling users to predict and optimize creep rupture life. This tool helps materials scientists and industrialists prevent failures in high-temperature applications and design steel compositions with enhanced creep resistance. Full article

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15 pages, 10067 KiB

Open AccessArticle

Effects of a Welding Wire Containing Er or Sc on the Microstructure, Mechanical Properties, and Corrosion Resistance of the 5xxx Aluminum Alloy MIG Joint

by Cunwei Zou, Ruizhi Wu, Xinhe Yang, Zhikun Ma and Legan Hou

Metals 2025, 15(3), 287; https://doi.org/10.3390/met15030287 - 6 Mar 2025

Abstract

The development of MIG (metal inert gas) welding for five-series aluminum alloys primarily involves the improvement and optimization of welding processes. Building upon research findings regarding the enhancement of aluminum alloy properties through the use of scandium (Sc) and erbium (Er), our study [...] Read more.

The development of MIG (metal inert gas) welding for five-series aluminum alloys primarily involves the improvement and optimization of welding processes. Building upon research findings regarding the enhancement of aluminum alloy properties through the use of scandium (Sc) and erbium (Er), our study incorporates Sc and Er into the welding wire to examine their impact on welding quality. The results show that the introduction of Er and Sc results in grain refinement from 47 µm to 29 µm and 31 µm, respectively. Grain refinement is mainly attributed to the heterogeneous nucleation of submicron-sized, coherent Al₃Er and Al₃Sc phases with L12 structure. The ultimate tensile strength (UTS), fracture elongation EI [%], and microhardness of joints welded with Er-containing and Sc-containing filler wires exhibit significant enhancements due to the refinement strengthening and dispersion strengthening. Joints welded with the filler wires containing Er and Sc display reduced corrosion current density and higher corrosion potential. The enhanced corrosion resistance comes from the formation of a denser oxide film and the equilibrium in the potential difference between the precipitated phases (Al₃Er and Al₃Sc) and the matrix. Filler wires containing Er and Sc have almost similar effects on improvements of the MIG welding joints. Full article

(This article belongs to the Special Issue Manufacturing Processes of Metallic Materials)

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17 pages, 6445 KiB

Open AccessArticle

Influence of B₂O₃ on the Viscosity and Melt Structure of CaO-SiO₂-M₂O (M = Li, Na)-Based Slags

by Jinhui Wang, Jie Qi, Yuanxin Shi, Yingying Dou and Chengjun Liu

Metals 2025, 15(3), 286; https://doi.org/10.3390/met15030286 - 6 Mar 2025

Abstract

In the process of continuous casting, especially high-speed continuous casting, the inflow state of the mold flux is particularly important. The fluxing agent is one of the most important factors affecting the flow state. The influence of the typical fluxing agent B₂ [...] Read more.

In the process of continuous casting, especially high-speed continuous casting, the inflow state of the mold flux is particularly important. The fluxing agent is one of the most important factors affecting the flow state. The influence of the typical fluxing agent B₂O₃ on the viscous characteristics and melt structure of the fluorine-free CaO-SiO₂-M₂O (M = Li, Na) system was analyzed. The following conclusions were drawn. In the CaO-SiO₂-Na₂O slags, with the increasing addition of B₂O₃, the viscosity, breaking temperature, and polymerization degree of the slag show a gradually decreasing trend. When the mass fraction of B₂O₃ increased from 0 to 10%, the increase in two-dimensional [BO₃] structural units played a dominant role. When the mass fraction of B₂O₃ reached 15%, the network was affected by the increase in [BO₃] and the low-polymerized [SiO₄] tetrahedrons. The CaO-SiO₂-Li₂O slag system had a lower breaking temperature due to the formation of phases such as Li₂O·2B₂O₃, of a low melting temperature. The initial degree of depolymerization of the network was high. Upon increasing the addition of B₂O₃, the relative proportion of the network modifier structural units significantly increased, resulting in the enhanced instability of the network structure. As a result, the effect of [SiO₄]-polymerization was stronger than that of [BO₃]-depolymerization in maintaining the stability of the network structure. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology—Second Edition)

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23 pages, 10069 KiB

Open AccessArticle

Microstructural Evolution, Strengthening Mechanisms, and Fracture Behavior of Aluminum Composites Reinforced with Graphene Nanoplatelets and In Situ–Formed Nano-Carbides

by Rumyana Lazarova, Lubomir Anestiev, Yana Mourdjeva, Kateryna Valuiska and Veselin Petkov

Metals 2025, 15(3), 285; https://doi.org/10.3390/met15030285 - 5 Mar 2025

Abstract

The microstructure and mechanical properties of GNP-reinforced aluminum composites obtained by powder metallurgy and hot extrusion (at 400 °C, 500 °C, and annealing at 3 h at 610 °C), were investigated. It was found that: (i) depending on the processing applied, the composites [...] Read more.

The microstructure and mechanical properties of GNP-reinforced aluminum composites obtained by powder metallurgy and hot extrusion (at 400 °C, 500 °C, and annealing at 3 h at 610 °C), were investigated. It was found that: (i) depending on the processing applied, the composites showed an increase in yield strength (YS) and ultimate strength (US) of up to 283%, and 78%, respectively; (ii) depending on the size of the ex situ GNP and in situ Al₄C₃ reinforcements, two fracture mechanisms are observed: ductile and brittle–ductile; (iii) annealing for 3 h at 610 °C did not improve the mechanical properties; (iv) the plot of YS vs. the volume fraction of the GNP introduced showed a peculiar pattern not been reported so far. Theoretical analysis of the results showed: (1) the major contributor to the YS increase is the Hall–Petch mechanism; (2) the reinforcements contribution to YS, complements that of Hall–Petch; (3) the main contributor to the composite strength is GNP; (4) a critical size of the reinforcement exists, 1.43 nm, at which the YS is maximal, 260 MPa; (5) the increase in the processing temperature and time leads to Ostwald ripening and increase of Al₄C₃ size and deterioration of mechanical properties. Full article

(This article belongs to the Special Issue Powder Metallurgy of Metals and Alloys)

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17 pages, 7697 KiB

Open AccessArticle

Dynamic Compression and Blast Failure Behavior of a Biomimetic Novel Lattice with Vertex Modifications Made of 316L Stainless Steel

by Fei Zhou, Zhihua Xue and Xiaofei Cao

Metals 2025, 15(3), 284; https://doi.org/10.3390/met15030284 - 5 Mar 2025

Abstract

A novel 316L stainless steel Vertex Modified BCC (VM-BCC) lattice unit cell with attractive performance characteristics is developed. Lattice structure, as well as the sandwich panel, are constructed. Numerical simulation is utilized to simulate the quasi-static compression, dynamic compression and blast behavior considering [...] Read more.

A novel 316L stainless steel Vertex Modified BCC (VM-BCC) lattice unit cell with attractive performance characteristics is developed. Lattice structure, as well as the sandwich panel, are constructed. Numerical simulation is utilized to simulate the quasi-static compression, dynamic compression and blast behavior considering the rate-dependent properties, elastoplastic response and nonlinear contact. Finite element results are validated by comparing with the experimental results. Parametric studies are conducted to gain insight into the effects of loading velocity, equivalent TNT load and explosion distance on the dynamic behavior of the lattice pattern and sandwich panel. Testing results indicate that the proposed 316L stainless steel VM-BCC structure exhibits more superior plateau stress and specific energy absorption (SEA) than those of the BCC or Octet one. The proposed novel lattice will provide reference for improving the protective efficiency in key equipment fields and enhancing overall safety. Full article

(This article belongs to the Special Issue Fracture Mechanics of Materials—the State of the Art)

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22 pages, 20741 KiB

Open AccessArticle

Microstructure and Properties of Resistance Element Welded Joints of DP780 Steel and 6061 Aluminum Alloy

by Qinglong Wu, Yue Yang, Yingzhe Li, Qing Guo, Shuyue Luo and Zhen Luo

Metals 2025, 15(3), 283; https://doi.org/10.3390/met15030283 - 5 Mar 2025

Abstract

This study developed a metallurgical and mechanical hybrid resistance element welding (REW) method to fabricate lightweight Al/steel joints between 2.0 mm 6061 aluminum alloy and 1.2 mm DP780 steel, addressing critical challenges of interfacial intermetallic compounds (IMC layer thickness: 4.6–8.3 μm) in dissimilar [...] Read more.

This study developed a metallurgical and mechanical hybrid resistance element welding (REW) method to fabricate lightweight Al/steel joints between 2.0 mm 6061 aluminum alloy and 1.2 mm DP780 steel, addressing critical challenges of interfacial intermetallic compounds (IMC layer thickness: 4.6–8.3 μm) in dissimilar metal welding. In addition, the scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and electron probe microanalysis (EPMA) were used to observe the microstructure characteristics and element distribution. The lath martensite and solidification microstructure were observed in the steel-nugget zone and Al-nugget zone, respectively. Furthermore, the microhardness distribution, volume fraction of the α phase, tensile–shear load, and failure mode of REWed joint were studied. Process optimization demonstrated welding current’s pivotal role in joint performance, achieving a maximum tensile–shear load of 6914.1 N under 10 kA conditions with a button pull-out failure (BPF) mechanism. Full article

(This article belongs to the Special Issue Modeling and Mechanism Analysis of Welding Process for Metals)

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21 pages, 12165 KiB

Open AccessArticle

Microscopic Modeling of Interfaces in Cu-Mo Nanocomposites: The Case Study of Nanometric Metallic Multilayers

by Abdelhafid Akarou, Florence Baras and Olivier Politano

Metals 2025, 15(3), 282; https://doi.org/10.3390/met15030282 - 5 Mar 2025

Abstract

Nanocomposites composed of Cu and Mo were investigated by means of molecular dynamics (MD) simulations to study the incoherent interface between Cu and Mo. In order to select an appropriate potential capable of accurately describing the Cu-Mo system, five many-body potentials were compared: [...] Read more.

Nanocomposites composed of Cu and Mo were investigated by means of molecular dynamics (MD) simulations to study the incoherent interface between Cu and Mo. In order to select an appropriate potential capable of accurately describing the Cu-Mo system, five many-body potentials were compared: three Embedded Atom Method (EAM) potentials, a Tight Binding Second Moment Approximation (TB-SMA) potential, and a Modified Embedded Atom Method (MEAM) potential. Among these, the EAM potential proposed by Zhou in 2001 was determined to provide the best compromise for the current study. The simulated system was constructed with two layers of Cu and Mo forming an incoherent fcc-Cu(111)/bcc-Mo(110) interface, based on the Nishiyama–Wassermann (NW) and Kurdjumov–Sachs (KS) orientation relationships (OR). The interfacial energies were calculated for each orientation relationship. The NW configuration emerged as the most stable, with an interfacial energy of 1.83 J/m², compared to 1.97 J/m² for the KS orientation. Subsequent simulations were dedicated to modeling Cu atomic deposition onto a Mo(110) substrate at 300 K. These simulations resulted in the formation of a dense layer with only a few defects in the two Cu planes closest to the interface. The interfacial structures were characterized by computing selected area electron diffraction (SAED) patterns. A direct comparison of theoretical and numerical SAED patterns confirmed the presence of the NW orientation relationship in the nanocomposites formed during deposition, corroborating the results obtained with the model fcc-Cu(111)/bcc-Mo(110) interfaces. Full article

(This article belongs to the Special Issue Design and Development of Metal Matrix Composites)

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17 pages, 1584 KiB

Open AccessArticle

An Innovative Algorithm for Damage Mapping in Multiaxial Fatigue Using the Stress Scale Factor (SSF) Concept

by Francisco Bumba, Vitor Anes and Luis Reis

Metals 2025, 15(3), 281; https://doi.org/10.3390/met15030281 - 5 Mar 2025

Abstract

Predicting damage to materials under multiaxial fatigue is a complex challenge, especially when normal and shear stresses interact in dynamic and non-linear ways. Traditional methods often oversimplify these interactions, leading to less reliable fatigue predictions and limiting their usefulness in real-world applications. To [...] Read more.

Predicting damage to materials under multiaxial fatigue is a complex challenge, especially when normal and shear stresses interact in dynamic and non-linear ways. Traditional methods often oversimplify these interactions, leading to less reliable fatigue predictions and limiting their usefulness in real-world applications. To address this, we present a novel algorithm based on the principles of the Stress Scale Factor (SSF), designed to dynamically evaluate the relative contributions of normal and shear stresses to fatigue damage. By providing a more accurate mapping of multiaxial fatigue damage, this approach enables improved predictions of fatigue life. The methodology combines experimental insights with mathematical modeling to create a flexible and adaptive framework. By making it possible to map multiaxial fatigue damage with greater precision, this SSF-based approach not only enhances the understanding of fatigue behavior but also enables better design decisions. The result is safer, more reliable, and efficient structures across a range of applications. This study bridges the gap between theoretical methods and practical needs, offering engineers and researchers a powerful tool to improve fatigue analysis and optimize structural performance. Full article

(This article belongs to the Special Issue Novel Insights into Fatigue and Fracture Behavior of Metallic Materials)

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23 pages, 6226 KiB

Open AccessArticle

Optimizing FSP Parameters for AA5083/SiC Composites: A Comparative Analysis of Taguchi and Regression

by Oritonda Muribwathoho, Velaphi Msomi and Sipokazi Mabuwa

Metals 2025, 15(3), 280; https://doi.org/10.3390/met15030280 - 5 Mar 2025

Abstract

The fabrication of AA5083/SiC composites by the friction stir processing (FSP) method is the main objective of this study. The study looks at how the mechanical properties of the composites are affected by three important process parameters: traversal speed, rotational speed, and tilt [...] Read more.

The fabrication of AA5083/SiC composites by the friction stir processing (FSP) method is the main objective of this study. The study looks at how the mechanical properties of the composites are affected by three important process parameters: traversal speed, rotational speed, and tilt angle. The Taguchi L₉ design matrix was used to effectively investigate parameter effects, decreasing experimental trials and cutting expenses. Tensile testing measured tensile strength, whereas microhardness tests evaluated hardness. The findings showed that a maximum tensile strength of 243 MPa and a maximum microhardness of 94.80 HV were attained. The findings also showed that the optimal ultimate tensile strength (UTS) and percentage elongation (PE) were achieved at a tilt angle of 2°, a traverse speed of 30 mm per minute, and a rotating speed of 900 rev/min. On the other hand, a slightly greater traverse speed of 45 mm per minute was required to reach maximal microhardness (MH) with the same rotational speed and tilt angle. Analysis of variance (ANOVA) showed that rotational speed has a substantial impact on all mechanical properties, highlighting how important it is for particle dispersion and grain refining. This work is unique in that it systematically optimizes FSP parameters by using regression analysis and the Taguchi technique in addition to ANOVA. This allows for a better understanding of how these factors affect the mechanical properties of SiC-reinforced composites. The findings contribute to advancing the cost-effective fabrication of high-performance metal matrix composites for industrial applications requiring enhanced strength and durability. Full article

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18 pages, 2081 KiB

Open AccessArticle

Characterization of EAF and LF Slags Through an Upgraded Stationary Flowsheet Model of the Electric Steelmaking Route

by Ismael Matino, Alice Petrucciani, Antonella Zaccara, Valentina Colla, Maria Ferrer Prieto and Raquel Arias Pérez

Metals 2025, 15(3), 279; https://doi.org/10.3390/met15030279 - 4 Mar 2025

Abstract

The current, continuous increase in attention toward preservation of the environment and natural resources is forcing resource-intensive industries like steelworks to investigate new solutions to improve resource efficiency and promote the growth of a circular economy. In this context, electric steelworks, which inherently [...] Read more.

The current, continuous increase in attention toward preservation of the environment and natural resources is forcing resource-intensive industries like steelworks to investigate new solutions to improve resource efficiency and promote the growth of a circular economy. In this context, electric steelworks, which inherently implement circularity principles, are spending efforts to enhance valorization of their main by-product, namely slags. A reliable characterization of the slag’s composition is crucial for the identification of the best valorization pathway, but, currently, slag monitoring is often discontinuous. Furthermore, in the current period of transformation of steel production, preliminary knowledge of the effect of modifications of operating practices on slags composition is crucial to assessing the viability of these modifications. In this paper, a stationary flowsheet model of the electric steelmaking route is presented; this model enables joint monitoring of key variables related to process, steel and slags. For the estimation of the content of most compounds in slags, the average relative percentage error is below 20% for most of the considered steel families. Thus, the tool can be considered suitable for scenario analyses supporting slag valorization. Higher performance is achievable by exploiting more reliable data for model tuning. These data can be obtained via novel devices that gather more numerous and representative data on the amount and composition of slags. Full article

(This article belongs to the Special Issue Recent Advances in the Recycling and Reuse of Metallurgical Wastes and By-Products)

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19 pages, 3694 KiB

Open AccessReview

Review of the Properties and Degradation Mechanisms of Refractories in Aluminum Reduction Cells

by Mohamed Hassen Ben Salem, Gervais Soucy, Daniel Marceau, Antoine Godefroy and Sébastien Charest

Metals 2025, 15(3), 278; https://doi.org/10.3390/met15030278 - 4 Mar 2025

Abstract

This review examines the degradation of refractory materials in aluminum reduction cells, focusing specifically on contamination caused by the cryolite-based bath. Aluminosilicate refractories, particularly Ordinary Refractory Bricks, play a vital role in maintaining the structural integrity and thermal balance of these cells under [...] Read more.

This review examines the degradation of refractory materials in aluminum reduction cells, focusing specifically on contamination caused by the cryolite-based bath. Aluminosilicate refractories, particularly Ordinary Refractory Bricks, play a vital role in maintaining the structural integrity and thermal balance of these cells under demanding operational conditions. The interaction between the molten bath and refractory linings leads to chemical reactions and mineralogical changes that modify the mechanical and thermal properties of the material over time. The study integrates findings from industrial autopsies, laboratory experiments, and a comprehensive review of the existing literature to identify and analyze the mechanisms of degradation. By analyzing the findings obtained from these methodologies, this review explores how cryolitic infiltration triggers transformations that compromise performance and reduce the lifespan of refractory linings. Covering a broad temperature range (665–960 °C), the study addresses key challenges in understanding bath-induced contamination and provides insights into how to improve the durability and efficiency of refractory materials in aluminum production. Full article

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19 pages, 6589 KiB

Open AccessArticle

Atmospheric Corrosion Behavior of Typical Aluminum Alloys in Low-Temperature Environment

by Tengfei Cui, Jianguo Wu, Jian Song, Di Meng, Xiaoli Jin, Huiyun Tian and Zhongyu Cui

Metals 2025, 15(3), 277; https://doi.org/10.3390/met15030277 - 4 Mar 2025

Abstract

The atmospheric corrosion behavior of type 2024, 5083, 6061, and 7075 aluminum alloys in the Antarctic environment was investigated by outdoor exposure tests and indoor characterization. After one year of exposure to the Antarctic atmosphere, significant differences in surface corrosion states were observed [...] Read more.

The atmospheric corrosion behavior of type 2024, 5083, 6061, and 7075 aluminum alloys in the Antarctic environment was investigated by outdoor exposure tests and indoor characterization. After one year of exposure to the Antarctic atmosphere, significant differences in surface corrosion states were observed among the specimens. The results revealed that the corrosion rate of the 2024 aluminum alloy was the highest, reaching 14.5 g/(m²·year), while the 5083 aluminum alloy exhibited the lowest corrosion rate of 1.36 g/(m²·year). The corrosion products formed on the aluminum alloys exposed to the Antarctic environment were primarily composed of AlOOH and Al₂O₃. In the Antarctic atmosphere environment, the pits were dominated by a freezing–thawing cycle and salt deposition. The freezing–thawing cycle promotes the wedge effect of corrosion products at the grain boundary, resulting in exfoliation corrosion of high-strength aluminum alloys. Full article

(This article belongs to the Special Issue Corrosion of Metals: Behaviors and Mechanisms)

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12 pages, 468 KiB

Open AccessReview

Recent Hydrometallurgical Investigations to Recover Antimony from Wastes

by Francisco Jose Alguacil

Metals 2025, 15(3), 276; https://doi.org/10.3390/met15030276 - 3 Mar 2025

Abstract

Antimony is a chemical element with diverse uses that falls into the range of a critical raw material. Although it appears in nature as stibnite, the mining of this mineralogical species is rare or uncommon, and it is the element that is basically [...] Read more.

Antimony is a chemical element with diverse uses that falls into the range of a critical raw material. Although it appears in nature as stibnite, the mining of this mineralogical species is rare or uncommon, and it is the element that is basically recovered as a secondary material in the processing of various elements (such as gold and copper). Another source for the recovery of this element is the recycling of Sb-bearing wastes such as batteries and alloys. Once dissolved and in order to recover it from the different leachates, adsorption processes are the ones that seem to have, at least for the scientific community, the highest acceptance. This work reviews the most recent advances (in 2024) in the recovery of antimony from different sources using not only adsorption processes but also other technologies of practical interest. Full article

(This article belongs to the Special Issue Hydrometallurgical Processes for the Recovery of Critical Metals)

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11 pages, 4938 KiB

Open AccessArticle

Influence of Heat Treatment Temperature on the Electrochemical Properties of Cold-Rolled 0.2%C–3%Al–6/8.5%Mn–Fe Medium-Manganese Steel

by Jihui Luo and Huixin Zuo

Metals 2025, 15(3), 275; https://doi.org/10.3390/met15030275 - 3 Mar 2025

Abstract

The microstructure evolution, polarization curve and impedance of cold-rolled 0.2%C–3%Al–6/8.5%Mn–Fe steel under heat treatment temperatures of 600–800 °C holding 10 min were tested. The results show that the cold-rolled texture of the steel does not completely disappear at 600 °C and 650 °C, [...] Read more.

The microstructure evolution, polarization curve and impedance of cold-rolled 0.2%C–3%Al–6/8.5%Mn–Fe steel under heat treatment temperatures of 600–800 °C holding 10 min were tested. The results show that the cold-rolled texture of the steel does not completely disappear at 600 °C and 650 °C, exhibiting high charge transfer resistance R_c and corresponding corrosion potential E_corr. When the heat treatment temperature rises to 700 °C, the texture begins to be eliminated and the R_c begins to decrease, indicating a decrease in corrosion resistance. When the heat treatment temperature rises to 750 °C and 800 °C, it was found that the proportion of austenite begins to increase and the number of grain boundaries decreases, resulting in an increase in R_c and an improvement in the corrosion resistance of the steel. Compared to 6.5 Mn steel, the higher Mn content in 8.5 Mn steel results in better corrosion resistance after high-temperature heat treatment. Full article

(This article belongs to the Section Corrosion and Protection)

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17 pages, 4214 KiB

Open AccessArticle

Metallic Metamaterials for Reducing the Magnetic Signatures of Ships

by Fabio Distefano, Roberto Zivieri, Gabriella Epasto, Antonio Pantano and Vincenzo Crupi

Metals 2025, 15(3), 274; https://doi.org/10.3390/met15030274 - 3 Mar 2025

Abstract

In this study, the magnetic signatures of ship structures were investigated. The magnetic signature impacts both navigation safety and the health of the marine ecosystem. Reducing this signature is essential for minimising risks associated with navigation and protecting marine biodiversity. A finite element [...] Read more.

In this study, the magnetic signatures of ship structures were investigated. The magnetic signature impacts both navigation safety and the health of the marine ecosystem. Reducing this signature is essential for minimising risks associated with navigation and protecting marine biodiversity. A finite element model was developed to assess the magnetic signature of honeycomb sandwich panels for ship structures. A theoretical approach was proposed, and the predicted results were compared with the values obtained by the finite element analyses. Different types of structures were compared to evaluate the combined effect of materials and geometry on the magnetic signature. The finite element results and the theoretical predictions indicate that the use of metamaterial structures, consisting of honeycomb sandwich panels with a steel core and aluminium skins, produces a significant reduction of the ship magnetic signature compared to the one arising from a steel panel with the same bending stiffness. Full article

(This article belongs to the Special Issue Metallic Magnetic Materials: Manufacture, Properties and Applications)

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17 pages, 3797 KiB

Open AccessArticle

Influence of Sulfide Concentration on the Properties of Cr₃C₂-25(Ni20Cr) Cermet Coating on Al7075 Substrate

by Mieczyslaw Scendo

Metals 2025, 15(3), 273; https://doi.org/10.3390/met15030273 - 2 Mar 2025

Abstract

The influence of sulfide (S²⁻) concentration on the corrosion resistance of Cr₃C₂-25(Ni20Cr) cermet coating on Al7075 (EN, AW-7075) substrate (Cr₃C₂-25(Ni20Cr)/Al7075) was investigated. The coating was produced by the cold-sprayed (CS) method. The Cr [...] Read more.

The influence of sulfide (S²⁻) concentration on the corrosion resistance of Cr₃C₂-25(Ni20Cr) cermet coating on Al7075 (EN, AW-7075) substrate (Cr₃C₂-25(Ni20Cr)/Al7075) was investigated. The coating was produced by the cold-sprayed (CS) method. The Cr₃C₂-25(Ni20Cr)/Al7075 coatings were modified chemically in solutions containing thioacetic acid amide (TAA). The surface and microstructure of the specimens were both observed by a scanning electron microscope (SEM). The mechanical properties of the Cr₃C₂-25(Ni20Cr) coatings were characterized using microhardness (HV) measurements. The corrosion tests of the materials were carried out using the electrochemical method in a acidic chloride solution. The adsorbed (Me_mS_n)_ads layer effectively separates the Cr₃C₂-25(Ni20Cr)/Al7075 coating surface from contact with the aggressive corrosive environment. More than a twice lower value of corrosion rate (CW) was obtained for the Cr₃C₂-25(Ni20Cr)/Al7075 coating after exposure to the environment with 0.15 M TAA. Full article

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

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14 pages, 8263 KiB

Open AccessArticle

Microstructural, Electrochemical, Mechanical, and Biocompatibility Characterization of ReN Thin Films Synthesized by DC Sputtering on Ti6Al4V Substrates

by Willian Aperador, Giovany Orozco-Hernández, Jonnathan Aperador and Jorge Bautista-Ruiz

Metals 2025, 15(3), 272; https://doi.org/10.3390/met15030272 - 1 Mar 2025

Abstract

Thin films of ReN were synthesized by DC sputtering at different nitrogen pressures (120, 140, 160, and 180 mTorr) on silicon and Ti6Al4V substrates. The coatings were evaluated for their microstructural and mechanical properties. Additionally, the biocompatibility and electrochemical properties of the films [...] Read more.

Thin films of ReN were synthesized by DC sputtering at different nitrogen pressures (120, 140, 160, and 180 mTorr) on silicon and Ti6Al4V substrates. The coatings were evaluated for their microstructural and mechanical properties. Additionally, the biocompatibility and electrochemical properties of the films were studied using Hanks’ lactate solution at 37 °C. X-ray diffraction (XRD) confirmed the formation of cubic ReN with higher nitrogen content. The optimized nitrogen pressure (180 mTorr) allowed the complete formation of the cubic phase of ReN. Regarding electrochemical behavior, ReN coatings significantly improve corrosion resistance, reducing the corrosion rate as nitrogen content increases, reaching 0.0145 µm/year at 180 mTorr. Regarding mechanical properties, the deposited ReN films presented an optimal combination of hardness and elastic modulus for the highest nitrogen contents. Cell viability was assessed by comparing uncoated and coated samples using a live/dead staining assay, demonstrating the biocompatibility of the coatings. To complement this study, scanning electron microscopy (SEM) was used to analyze the protein–coating interaction and cell morphology on the surface of the samples. Full article

(This article belongs to the Special Issue Corrosion Behavior and Surface Engineering of Metallic Materials)

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18 pages, 25726 KiB

Open AccessArticle

Effect of Grain Size on Mechanical Properties and Deformation Mechanism of Nano-Polycrystalline Pure Ti Simulated by Molecular Dynamics

by Xiao Zhang, Adam Ibrahem Abdalrsoul Alduma, Faqi Zhan, Wei Zhang, Junqiang Ren and Xuefeng Lu

Metals 2025, 15(3), 271; https://doi.org/10.3390/met15030271 - 1 Mar 2025

Abstract

Nano- and microscale titanium and its alloys have potential applications in semiconductor-based micro-electromechanical systems due to their excellent mechanical properties. The uniaxial tensile mechanical properties and deformation mechanism of polycrystalline pure Ti with five different grain sizes measuring 6.74–19.69 nm were studied via [...] Read more.

Nano- and microscale titanium and its alloys have potential applications in semiconductor-based micro-electromechanical systems due to their excellent mechanical properties. The uniaxial tensile mechanical properties and deformation mechanism of polycrystalline pure Ti with five different grain sizes measuring 6.74–19.69 nm were studied via molecular dynamics simulation using the embedded-atom potential function method. The Hall–Petch relationships and the critical grain size of the polycrystalline pure Ti are given. The dislocation migration of grain boundaries is the main deformation mechanism when the grain size exceeds 16.61 nm, which causes a direct Hall–Petch effect. When grain sizes are smaller than 16.61 nm, grain boundary sliding is the preferred deformation mechanism, which causes an inverse Hall–Petch effect. The polycrystalline pure Ti shows the highest tensile strength and average flow stress of 2.70 GPa and 2.15 GPa, respectively, at the 16.61 nm grain size, which is the critical grain size in the Hall–Petch relationships. The polycrystalline Ti is at its highest strength when its grain size ranges from 16 to 17 nm. The current research provides a theoretical basis for the use of pure titanium in emerging technologies at the nanoscale. Full article

(This article belongs to the Special Issue Microstructure, Crystallography, and Mechanical Properties of Metallic Materials)

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