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Nodular Graphite Dissolution and Nucleus Observation
Shear-Punched Surface Layer Damage in Ultrahigh-Strength TRIP-Aided Steels with Bainitic Ferrite/Martensite Matrix
Mechanical Properties of AM vs. Wrought Ti6Al4V: A Study on Martensitic Alloy
Enhancing Mg Alloys for Bioimplants: Zn/Ca Ratio and Texture Synergy for Corrosion Resistance
Synthesis and Properties of Cu-Based Composites Reinforced with ZrB₂

Journal Description

Metals

Metals is an international, peer-reviewed, open access journal published monthly online by MDPI. The Portuguese Society of Materials (SPM), and the Spanish Materials Society (SOCIEMAT) are affiliated with Metals and their members receive a discount on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
Journal Rank: JCR - Q2 (Metallurgy and Metallurgical Engineering) / CiteScore - Q1 (Metals and Alloys)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.5 days after submission; acceptance to publication is undertaken in 2.6 days (median values for papers published in this journal in the first half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Companion journals for Metals include: Compounds and Alloys.

Impact Factor: 2.6 (2023); 5-Year Impact Factor: 2.7 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2075-4701

Latest Articles

14 pages, 1637 KiB

Open AccessArticle

Real-Time Modeling for Design and Control of Material Additive Manufacturing Processes

by Amir M. Horr

Metals 2024, 14(11), 1273; https://doi.org/10.3390/met14111273 - 8 Nov 2024

The use of digital twin and shadow concepts for industrial material processes has introduced new approaches to bridge the gap between physical and cyber manufacturing processes. Consequently, many multidisciplinary areas, such as advanced sensor technologies, material science, data analytics, and machine learning algorithms, [...] Read more.

The use of digital twin and shadow concepts for industrial material processes has introduced new approaches to bridge the gap between physical and cyber manufacturing processes. Consequently, many multidisciplinary areas, such as advanced sensor technologies, material science, data analytics, and machine learning algorithms, are employed to create these hybrid systems. Meanwhile, new additive manufacturing (AM) processes for metals and polymers, based on emerging technologies, have shown promise for the manufacturing of sophisticated parts with complex geometries. These processes are undergoing a major transformation with the advent of digital technology, hybrid physical-data-driven modeling, and fast-reduced models. This study presents a fresh perspective on hybrid physical-data-driven and reduced order modeling (ROM) techniques for the digitalization of AM processes within a digital twin concept. The main contribution of this study is to demonstrate the benefits of ROM and machine learning (ML) technologies for process data handling, optimization/control, and their integration into the real-time assessment of AM processes. Therefore, a novel combination of efficient data-solver technology and an architecturally designed neural network (NN) module is developed for transient manufacturing processes with high heating/cooling rates. Furthermore, a real-world case study is presented, showcasing the use of hybrid modeling with ROM and ML schemes for an industrial wire arc AM (WAAM) process. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing and Their Applications (2nd Edition))

17 pages, 3072 KiB

Open AccessArticle

Metallic Metamaterials with Auxetic Properties: Re-Entrant Structures

by Julian Plewa, Małgorzata Płońska and Grzegorz Junak

Metals 2024, 14(11), 1272; https://doi.org/10.3390/met14111272 (registering DOI) - 8 Nov 2024

The present article is an exploration of metamaterial structures exhibiting auxetic properties. The study shows the effect of three geometric parameters of re-entrant auxetic cells, namely, the internal initial cell angle (θ₀), the strut length ratio h/l, and the degree of [...] Read more.

The present article is an exploration of metamaterial structures exhibiting auxetic properties. The study shows the effect of three geometric parameters of re-entrant auxetic cells, namely, the internal initial cell angle (θ₀), the strut length ratio h/l, and the degree of opening of the unit cells expressed by the change in the θ angle, on the value of the Poisson’s ratio. It combines theoretical insights into physical re-entrant auxetic structures with the demonstration of structures that can be subjected to cyclic loading without being damaged. The experimental section features the results of the compression tests of a symmetrical structure made up of four re-entrant cells and tensile tests of a flat mesh structure of size 4 × 4. In the mesh structure, a modification was applied to the re-entrant cells, creating arched strut connections. It was shown that the value of the maximum load for such structures depends on the bending angle and the length of the inclined strut. The mesh structure was created using torsion springs. Its cyclic tension for different amplitudes yielded Poisson’s ratio values in the range of −1.4 to −1.7. These modifications have enabled stable, elastic, and failure-free cyclical changes of the structure’s dimensions under load. Full article

(This article belongs to the Special Issue Simulation and Optimization Methods in Machining and Structure/Material Design)

21 pages, 13790 KiB

Open AccessArticle

Characterisation of Varying Iron Ores and Their Thermal Decomposition Kinetics Under HIsarna Ironmaking Conditions

by Philipp Leerhoff, Johannes C. Brouwer, Amir Mohseni Armaki, Christiaan Zeilstra, Koen Meijer, Jan van der Stel, Shoshan T. Abrahami, Neslihan Dogan and Yongxiang Yang

Metals 2024, 14(11), 1271; https://doi.org/10.3390/met14111271 (registering DOI) - 8 Nov 2024

In the pre-reduction cyclone of the HIsarna process, both thermal decomposition and gas reduction of the injected iron ores occur simultaneously at gas temperatures of 1723–1773 K. In this study, the kinetics of the thermal decomposition of three iron ores (namely OreA, OreB [...] Read more.

In the pre-reduction cyclone of the HIsarna process, both thermal decomposition and gas reduction of the injected iron ores occur simultaneously at gas temperatures of 1723–1773 K. In this study, the kinetics of the thermal decomposition of three iron ores (namely OreA, OreB and OreC) for HIsarna ironmaking were analysed as an isolated process with a symmetrical thermogravimetric analyser (TGA) under an inert atmosphere. Using various methods, the chemical and mineralogical composition, particle size distribution, morphology and phase distribution of the ores were analysed. The ores differ in their mineralogy and morphology, where OreA only contains hematite as iron-bearing phase and OreB and OreC include goethite and hematite. To obtain the kinetic parameters in non-isothermal conditions, the Coats–Redfern Integral Method was applied for heating rates of 1, 2 and 5 K/min and a maximum temperature of 1773 K. The TGA results indicate that goethite and hematite decomposition occur as a two-stage process in an inert atmosphere of Ar. The proposed reaction mechanism for the first stage of goethite decomposition is chemical reaction with an activation energy ranging from 46.55 to 60.38 kJ/mol for OreB and from 69.90 to 134.47 kJ/mol for OreC. The proposed reaction mechanism for the second stage of goethite decomposition is diffusion, showing an activation energy ranging between 24.43 and 44.76 kJ/mol for OreB and between 3.32 and 23.29 kJ/mol for OreC. In terms of hematite decomposition, only the first stage was analysed. The proposed reaction mechanism is chemical reaction control. OreA shows an activation energy of 545.47 to 670.50 kJ/mol, OreB one of 587.68 to 831.54 kJ/mol and OreC one of 424.31 to 592.32 kJ/mol. Full article

(This article belongs to the Special Issue Feature Papers in Extractive Metallurgy)

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14 pages, 29305 KiB

Open AccessArticle

A Comparative Study on Laser Cutting Performance with Varying Speeds at 10 M Underwater

by Danbi Song, Jungsoo Choi, Sujin Lee, Ryoonhan Kim and Induck Park

Metals 2024, 14(11), 1270; https://doi.org/10.3390/met14111270 - 8 Nov 2024

Despite the dismantling structures that are submerged to significant depths of water during the decommissioning of nuclear power plants, there is limited research on deep-water laser cutting processes. A self-designed pressurized chamber was used in this study and successfully conducted the world’s first [...] Read more.

Despite the dismantling structures that are submerged to significant depths of water during the decommissioning of nuclear power plants, there is limited research on deep-water laser cutting processes. A self-designed pressurized chamber was used in this study and successfully conducted the world’s first laser cutting experiment in a simulated 10 m water depth environment. laser cutting was performed in a 10 m underwater environment, and the cutting efficiency was compared to that observed in a 1 m underwater environment. Therefore, A 100 mm thickness of 304 stainless steel was successfully cut underwater, and the highest cutting speed of 100 mm/min was achieved. The result indicates that, as the cutting speed increased during underwater laser cutting, both the heat input and the mass flow rate of the assist gas decreased, resulting in a narrower rear kerf width and an ineffective evacuation of the molten metal. Full article

(This article belongs to the Special Issue Advances in Metal Cutting and Machining Processes)

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15 pages, 3880 KiB

Open AccessArticle

Trade-Off Between Wear/Corrosion Performance and Mechanical Properties in D-AlNiCo Poly-Quasicrystals Through CNT Addition to the Microstructure

by Seyedmehdi Hosseini, Pavel Novák, Mostafa Alishahi, Zdeněk Kačenka and Petr Šittner

Metals 2024, 14(11), 1269; https://doi.org/10.3390/met14111269 - 8 Nov 2024

An ultrafine-grained Al₇₁Ni_14.5Co_14.5/CNT poly-quasicrystal (QC/CNT) composite was synthesized using spark plasma sintering of powder components developed through electroless Ni-P/CNT plating of Co particles and mechanical alloying. The performance of the synthesized samples was studied using various testing [...] Read more.

An ultrafine-grained Al₇₁Ni_14.5Co_14.5/CNT poly-quasicrystal (QC/CNT) composite was synthesized using spark plasma sintering of powder components developed through electroless Ni-P/CNT plating of Co particles and mechanical alloying. The performance of the synthesized samples was studied using various testing methods, such as room temperature/hot compression, wear, and corrosion tests. The results were compared to the properties of alloy samples fabricated from raw and coated powders (without CNTs). The wear rate and friction coefficient of the quasicrystalline samples improved significantly due to the contribution of the CNTs. The wear rate of the CNT-containing specimens was 0.992 × 10⁻⁴ mm³/N/m, which is 47.1% lower than that of the QC sample. The positive impact of the CNTs on the corrosion potential and current density was further validated by the potentiodynamic polarization tests in a saline solution. However, these improvements in surface properties came at the cost of a 21.5% reduction in compressive strength, although the compressive strength still remained above 1.1 GPa at 600 °C. The results highlight an interesting trade-off between surface properties and mechanical strength, pointing toward the development of materials suitable for extreme conditions. Full article

(This article belongs to the Special Issue Alloy Design and Its Performance Trade-Offs)

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18 pages, 5457 KiB

Open AccessArticle

Lithography-Based Metal Manufacturing of Copper: Influence of Exposure Parameters on Green Part Strength

by Jakob Scheibler, Alina Sabine Kosmehl, Thomas Studnitzky, Chongliang Zhong and Thomas Weißgärber

Metals 2024, 14(11), 1268; https://doi.org/10.3390/met14111268 - 8 Nov 2024

Copper’s high thermal and electrical conductivity enables its application in heat exchangers and high-frequency components. For those applications, additive manufacturing has advantages with respect to functional integration, miniaturization, and reduced waste. However, the processing of copper is a challenge for established laser-based processes [...] Read more.

Copper’s high thermal and electrical conductivity enables its application in heat exchangers and high-frequency components. For those applications, additive manufacturing has advantages with respect to functional integration, miniaturization, and reduced waste. However, the processing of copper is a challenge for established laser-based processes since copper’s high reflectivity impedes energy input. Sinter-based additive manufacturing processes do not exhibit this limitation since the energy for the fusion of material is applied by thermal energy during sintering. This makes them an ideal candidate for copper manufacturing. In the following work, Lithography-based Metal Manufacturing (LMM) of copper is demonstrated. Curing behavior is investigated by single-layer exposure (SLE) tests measuring curing thickness for different loading factors, particle sizes, and exposure times. Bending strength is investigated as a function of exposure time, loading factor, and orientation in the building space. A higher exposure time and lower loading factors increase bending strength. Furthermore, samples with different loading factors are produced to measure the impact of the loading factor on sintered density. For these parameters, no clear trend is demonstrated. Full article

(This article belongs to the Special Issue The Next Generation of Metal Additive Manufacturing)

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21 pages, 6371 KiB

Open AccessArticle

Ruta graveolens Plant Extract as a Green Corrosion Inhibitor for 304 SS in 1 M HCl: Experimental and Theoretical Studies

by Sonia Estefanía Hernández-Sánchez, Juan Pablo Flores-De los Rios, Humberto Alejandro Monreal-Romero, Norma Rosario Flores-Holguin, Luz María Rodríguez-Valdez, Mario Sánchez-Carrillo, Anabel D. Delgado and Jose G. Chacón-Nava

Metals 2024, 14(11), 1267; https://doi.org/10.3390/met14111267 - 8 Nov 2024

This study evaluated the corrosion inhibitory effects of Ruta graveolens leaf extract for 304 stainless steel in 1 M HCl. The analysis of the leaf extract using HPLC indicated that the primary compounds present in the leaf extract were rutin, caffeic acid, p-coumaric [...] Read more.

This study evaluated the corrosion inhibitory effects of Ruta graveolens leaf extract for 304 stainless steel in 1 M HCl. The analysis of the leaf extract using HPLC indicated that the primary compounds present in the leaf extract were rutin, caffeic acid, p-coumaric acid, and apigenin. The inhibition efficiency (IE%) of the extract was studied using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and computational simulation (density functional theory, DFT). The effects of the inhibitor concentration and solution temperature were investigated. The results indicated that the IE% increased for increasing concentrations of the extract, while the reverse was true with increasing temperatures. At 25 °C and a 600 ppm extract concentration, the results indicated a maximum inhibition efficiency of 95%, 98%, and 96% by weight loss, potentiodynamic polarization, and EIS techniques, respectively. SEM observations showed a significant change in the surface morphology of the 304 SS with and without the addition of the inhibitor compound. At all temperatures, the adsorption of the inhibitor components onto the 304 SS surface was found to follow the Langmuir isotherm model, and the inhibition process was governed by physical adsorption. Furthermore, chemical interactions between the inhibitor and the 304 SS steel surface were elucidated via density functional theory (DFT) calculations. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion and Protection of Metallic Materials)

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23 pages, 8405 KiB

Open AccessArticle

The Concept of the Estimation of Phase Diagrams (An Optimised Set of Simplified Equations to Estimate Equilibrium Liquidus and Solidus Temperatures, Partition Ratios, and Liquidus Slopes for Quick Access to Equilibrium Data in Solidification Software) Part I: Binary Equilibrium Phase Diagrams

by Gergely Kőrösy, András Roósz and Tamás Mende

Metals 2024, 14(11), 1266; https://doi.org/10.3390/met14111266 - 7 Nov 2024

This paper presents equations derived from thermodynamic equations for calculating the liquidus and solidus temperatures, the liquidus slope, and the partition ratio for solidification simulations. The constants of these equations can be easily determined from measurement data obtained by digitalisation from known diagrams [...] Read more.

This paper presents equations derived from thermodynamic equations for calculating the liquidus and solidus temperatures, the liquidus slope, and the partition ratio for solidification simulations. The constants of these equations can be easily determined from measurement data obtained by digitalisation from known diagrams or can be calculated using a CALPHAD-based software. ESTPHAD has a hierarchical system; the developed functions of the binary systems are used in the calculation of the functions of the ternary systems, the functions of the ternary systems in the calculation of the function of quaternary systems, and so on. The developed method is demonstrated by processing the liquidus and solidus of Si–Ge isomorphous and Al–Mg and Al–Si eutectic equilibrium phase diagrams. The use of this method for calculating the functions of ternary systems will be shown in Part II. The advantages of this method are that the equations are simple, can be determined very quickly, and can be built into the simulation software very easily. The most significant advantage is that the calculation time is shorter by some order of magnitude than that of a CALPHAD-type calculation. Full article

(This article belongs to the Special Issue Thermodynamic Assessment of Alloy Systems)

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13 pages, 9043 KiB

Open AccessArticle

Microstructure Evolution and Performance of AA2024 Alloy Through Wire-Arc Additive Manufacturing Under Different Heat Inputs

by Jin Yang and Aimin Wang

Metals 2024, 14(11), 1265; https://doi.org/10.3390/met14111265 - 7 Nov 2024

Wire-arc additive manufacturing (WAAM) is widely applied in the aerospace, automotive, defense, and other industries. As such, the study of the formation and evolution mechanism of grains to achieve precise control over the performance of additive parts is important. In this study, AA2024 [...] Read more.

Wire-arc additive manufacturing (WAAM) is widely applied in the aerospace, automotive, defense, and other industries. As such, the study of the formation and evolution mechanism of grains to achieve precise control over the performance of additive parts is important. In this study, AA2024 high-strength Al alloy wire was used to produce WAAM specimens under different heat inputs by varying different parameters. Subsequently, their microstructure, phases, and tensile properties were analyzed. The results indicated that the predominant crystal comprised cellular crystals, columnar crystals and dendritic crystals. At a heat input of 5500–6200 kJ m⁻¹, the internal morphology of the specimen, characterized by the significant presence of fine cellular crystals, was predominantly favorable. As the heat input increased, α (Al) and θ (CuAl₂) phases were increasingly identified within the specimens, the grid-like distribution of the θ phase along the crystal boundaries became clearer, and the θ′ phase precipitation decreased. Solution treatment and aging of the specimen produced using the optimal WAAM parameters resulted in an ultimate tensile strength (UTS) of 398 MPa, yield strength (YS) of 284 MPa, and elongation of 11.3%. The results should serve as a basis for selecting suitable WAAM process parameters. Full article

(This article belongs to the Special Issue Advance in Wire-Based Additive Manufacturing of Metal Materials)

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11 pages, 7681 KiB

Open AccessArticle

The Evolution of Cube Texture in Directionally Solidified Fe-3.0 wt. % Si Alloy Assisted by a High Static Magnetic Field

by Chunmei Liu, Zijian Chen, Hongyu Li, Wenhao Lin, Meilong Feng, Tianxiang Zheng, Bangfei Zhou and Yunbo Zhong

Metals 2024, 14(11), 1264; https://doi.org/10.3390/met14111264 - 7 Nov 2024

The effect of a high static magnetic field (HSMF) on the evolution of cube texture in directionally solidified Fe-3.0 wt. % Si alloy was studied. The results show that the <001> crystal orientation of an α-Fe single crystal was parallel to the direction [...] Read more.

The effect of a high static magnetic field (HSMF) on the evolution of cube texture in directionally solidified Fe-3.0 wt. % Si alloy was studied. The results show that the <001> crystal orientation of an α-Fe single crystal was parallel to the direction of the HSMF, and a sharp cube texture was successfully formed in the final ingot. With the increase in growth speed, the main texture of the Fe-3.0 wt. % Si alloy evolved in the way of <001>→<081>→<120> along the pulling direction when an HSMF was applied. The orientation transition was attributed to the magnetocrystalline anisotropy of the α–Fe crystal during the directional solidification process. As a result of texture optimization, the specimens with an HSMF had higher saturation magnetization and permeability than the sample without an HSMF. Furthermore, a new creative method to tailor the cube texture of Fe-based alloys during the directional solidification process assisted by an HSMF is proposed. Full article

(This article belongs to the Section Crystallography and Applications of Metallic Materials)

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8 pages, 221 KiB

Open AccessEditorial

Recent Advances in Metallurgical Extractive Processes

by Norman Toro, Edelmira Gálvez and Ricardo I. Jeldres

Metals 2024, 14(11), 1263; https://doi.org/10.3390/met14111263 - 7 Nov 2024

Mining is an indisputable pillar of the world economy, and it faces constant challenges that demand technological innovations and continuous adaptation [...] Full article

(This article belongs to the Topic Recent Advances in Metallurgical Extractive Processes)

17 pages, 9389 KiB

Open AccessArticle

Fabrication of Ultrathin Al Foils by Accumulative Pack Rolling: Influence of Pack Materials

by Ning Nie, Rui Wang, Guanyu Deng, Hui Wang, Pengfei Wang, Anh Kiet Tieu, Huijun Li and Lihong Su

Metals 2024, 14(11), 1262; https://doi.org/10.3390/met14111262 - 7 Nov 2024

Ultrathin metal foils are essential for applications requiring miniaturization across modern industry. Nevertheless, it is challenging for conventional rolling mills and conventional rolling methods to reduce the thickness of single-layer foils to a scale approaching just a few micrometers. This difficulty arises from [...] Read more.

Ultrathin metal foils are essential for applications requiring miniaturization across modern industry. Nevertheless, it is challenging for conventional rolling mills and conventional rolling methods to reduce the thickness of single-layer foils to a scale approaching just a few micrometers. This difficulty arises from a range of inherent factors, including the elastic modulus, diameter of the rollers, resistance of rolled materials, and friction coefficient. To address these limitations, an accumulative pack rolling (APR) method has been developed in this work to fabricate ultrathin metal foils. Al foils down to ~2 µm have been successfully fabricated by using Al, Ta, and stainless steel (SS) as pack materials. The effects of the pack sheets on surface morphology, thickness reduction, and microstructural evolution were investigated. Key surface roughening behaviors, including ridging and particle-like surface roughening, were observed on the inner surface, which influences the roughening and thinning behavior of the target Al foils. This study also provides insights into surface roughening mechanisms, including rolling marks, ridging, and particle-like roughening, and demonstrates the critical role of pack sheet materials in controlling plastic instability, achieving uniform thickness reduction in ultrathin foils, and preventing severe deterioration of surface flatness during the APR process. Full article

(This article belongs to the Section Metal Casting, Forming and Heat Treatment)

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13 pages, 13688 KiB

Open AccessArticle

Weakening the Anisotropic Property and Refining Prior-β Grains via Hammer Peening Treatment During Wire Arc Additively Manufacturing of Ti-6Al-4V

by Guo Xian, Jingbang Pan, Junghoon Lee and Namhyun Kang

Metals 2024, 14(11), 1261; https://doi.org/10.3390/met14111261 - 7 Nov 2024

In Wire Arc Additive Manufacturing (WAAM), solidification grain morphology in titanium alloy tends to be columnar rather than equiaxed due to heat dissipation and repeated thermal cycles. This study demonstrates improved microstructure and anisotropic properties in Ti-6Al-4V specimens fabricated by WAAM and treated [...] Read more.

In Wire Arc Additive Manufacturing (WAAM), solidification grain morphology in titanium alloy tends to be columnar rather than equiaxed due to heat dissipation and repeated thermal cycles. This study demonstrates improved microstructure and anisotropic properties in Ti-6Al-4V specimens fabricated by WAAM and treated with hammer peening, resulting in a transition from columnar grains to fine equiaxed grains (~300 μm) in both single-pass and four-bead WAAM walls. The anisotropic elongation decreased by approximately 7%, and tensile strength along the building direction decreased by ~50 MPa for a single-pass wall. Additionally, small and large equiaxed prior-β grains appeared alternately due to the combined effect of hammer peening and welding deposition. The region can be categorized into three parts (MAX, MED, MIN) based on the degree of plastic strain characterized by KAM mapping of EBSD data. In current WAAM parameters, the ratio of strong (~1.5 mm) deformation field (MAX) is about 50% within one deposition layer (MAX+MIN), suggesting a new approach for producing equiaxed prior-β grains. We expect that this method will be applicable for transforming the prior-β grains from columnar to equiaxed. Furthermore, the distribution of plastic strain and phase transformation mechanisms offers innovative approaches to optimize the hammer peening process, with potential applications to optimize the process for more complex components in the aerospace and power plant industries. Full article

(This article belongs to the Special Issue Advance in Wire-Based Additive Manufacturing of Metal Materials)

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14 pages, 880 KiB

Open AccessReview

Mechanochemical Treatment for the Extraction of Lithium from Hard Rock Minerals: A Comprehensive Review

by Yuik Eom, Laurence Dyer, Aleksandar N. Nikoloski and Richard Diaz Alorro

Metals 2024, 14(11), 1260; https://doi.org/10.3390/met14111260 - 7 Nov 2024

Lithium (Li) extraction from Li hard rock minerals involves thermal activation at elevated temperatures and the use of corrosive reagents. The reagents can damage the environment if they are not adequately contained as part of the process, and the high temperatures require large [...] Read more.

Lithium (Li) extraction from Li hard rock minerals involves thermal activation at elevated temperatures and the use of corrosive reagents. The reagents can damage the environment if they are not adequately contained as part of the process, and the high temperatures require large amounts of energy, which can contribute to greenhouse gas emissions unless renewable energy sources are used. These concerns have motivated research into many alternative methods to partially or completely replace the conventional process while maintaining or enhancing the Li extraction rate. Mechanochemistry is one of these alternative methods, as it has the potential to increase the reactivity of Li resources with reagents while reducing the need for corrosive reagents. Mechanochemistry has been applied to mineral processing, particularly introduced as the pre-treatment method before pyro- or hydrometallurgical processes, for several decades. In recent years, a few studies about direct Li extraction from mechanochemically activated hard rock minerals utilizing various co-grinding additives have been reported. This review deals with the application of mechanochemistry to process the Li-bearing hard rock minerals, spodumene and lepidolite, and the mechanisms of the mechanochemical treatment. Full article

(This article belongs to the Special Issue Toward Achieving a Carbon-Neutral Society: Beneficiation and Extractive Metallurgy for Producing Critical Metals from Ores/Wastes)

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18 pages, 2540 KiB

Open AccessArticle

Biotechnological Tool for Metal(loid)s as Cd, Cu, Ni, and P Management with Multiple Approaches: Bioremediation, Recovery of Raw Materials, and Food Safety

by Adalgisa Scotti, Ana Rosa Castaño Gañan, Vanesa Analía Silvani, Andrea Juarez, Gabriela Coria, Sofía Utge Perri, Roxana Paola Colombo, Inmaculada García-Romera, María Luisa Izaguirre-Mayoral, Alicia Godeas and Stefano Ubaldini

Metals 2024, 14(11), 1259; https://doi.org/10.3390/met14111259 - 6 Nov 2024

Contaminated soils are a challenge for implementing biotechnology in bioremediation, the recovery of Critical and Strategic Raw Materials (CRMs and SRMs), and food security. European Union (EU) Governments have established strict limits on As, Pb, Cd, and Hg in foods (Document 32023R0915) and [...] Read more.

Contaminated soils are a challenge for implementing biotechnology in bioremediation, the recovery of Critical and Strategic Raw Materials (CRMs and SRMs), and food security. European Union (EU) Governments have established strict limits on As, Pb, Cd, and Hg in foods (Document 32023R0915) and requested the recovery of 34 CRMs within a circular economy (CE) (5th CRMs list). This study proposed a biotechnological tool for the decontamination of soil with heavy metal(loid)s by arbuscular mycorrhizal (AM)-assisted phytoextraction and the subsequent recovery of CRMs or by phytostabilization to prevent their entry into the food chain. It consisted of placing Baccharis salicifolia plants, inoculated or non-inoculated with AM fungi, into bioreactors (BRs) containing mining soil with Cd, Ni, and Cu, according to the Argentinian Patent (AR090183B1). The bioextractive potential (BP) was also estimated at the highest Technological Readiness Level (TRL) using a vegetable depuration module (VDM, TRL 6). Inoculated plants showed significantly higher aerial bioaccumulation coefficients (Cd: 68.62; P: 2.99; Ni: 2.51; Cu: 0.18) in BRs, and the BP values reached 1.16 g, 9.75 g, 2.40 g, and 213.1 g for Ni, Cd, Cu, and P, respectively. Finally, these CRMs and SRMs could be recovered from biomass through hydrometallurgy within a CE framework. Full article

(This article belongs to the Special Issue Recovery of Critical Raw Materials from Industrial Wastes by Advanced Methods)

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13 pages, 2718 KiB

Open AccessArticle

Crystal Chemistry at Interfaces Between Liquid Al and Polar SiC{0001} Substrates

by Changming Fang and Zhongyun Fan

Metals 2024, 14(11), 1258; https://doi.org/10.3390/met14111258 - 6 Nov 2024

Silicon carbide (SiC) has been widely added into light metals, e.g., Al, to enhance their mechanical performance and corrosion resistance. SiC particle-reinforced metal matrix composites (SiC-MMCs) exhibit low weight/volume ratios, high strength/hardness, high corrosion resistance, and thermal stability. They have potential applications in [...] Read more.

Silicon carbide (SiC) has been widely added into light metals, e.g., Al, to enhance their mechanical performance and corrosion resistance. SiC particle-reinforced metal matrix composites (SiC-MMCs) exhibit low weight/volume ratios, high strength/hardness, high corrosion resistance, and thermal stability. They have potential applications in aerospace, automobiles, and other specialized equipment. The macro-mechanical properties of Al/SiC composites depend on the local structures and chemical interactions at the Al/SiC interfaces at the atomic level. Moreover, the added SiC particles may act as potential nucleation sites during solidification. We investigate local atomic ordering and chemical interactions at the interfaces between liquid Al (Al(l) in short) and polar SiC substrates using ab initio molecular dynamics (AIMD) methods. The simulations reveal a rich variety of interfacial interactions. Charge transfer occurs from Al(l) to C-terminating atoms (Δq = 0.3e/Al on average), while chemical bonding between interfacial Si and Al(l) atoms is more covalent with a minor charge transfer of Δq = 0.04e/Al. The prenucleation at both interfaces is moderate with three to four recognizable layers. The information obtained here helps increase understanding of the interfacial interactions at Al/SiC at the atomic level and the related macro-mechanical properties, which is helpful in designing novel SiC-MMC materials with desirable properties and optimizing related manufacturing and machining processes. Full article

(This article belongs to the Special Issue Multi-scale Simulation of Metallic Materials (2nd Edition))

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15 pages, 6278 KiB

Open AccessArticle

Model of Dynamic Mechanical Parameters and Vibration Analysis in Hot Rolling

by Ming Zhang, Zihao Huang and Yanbo Yang

Metals 2024, 14(11), 1257; https://doi.org/10.3390/met14111257 - 6 Nov 2024

As the core equipment of metal shaping processing, the vibration problem of rolling mill seriously affects the product quality and production efficiency. To address the problem of the limited prediction of mill vibration due to small sample data in non-steady states, we propose [...] Read more.

As the core equipment of metal shaping processing, the vibration problem of rolling mill seriously affects the product quality and production efficiency. To address the problem of the limited prediction of mill vibration due to small sample data in non-steady states, we propose to predict dynamic mechanical parameters (rolling force and rolling torque) based on the TCN-LSTM step strategy transfer model. The prediction accuracies of the TCN-LSTM step strategy transfer model under 1000 sets of training data reach 95.8% and 93.2%, respectively, and at the same time, it saves the time of training and regulation of the deep learning model and can better meet the needs of online prediction. The horizontal-torsion hot rolling vibration model is further established to quantitatively analyze the relationship between process parameters and mill vibration. The experimental results show that with the vibration suppression measures of 10% reduction of the rolling speed and 10% reduction of the entrance thickness, the horizontal vibration displacement amplitude is reduced from 0.687 × 10⁻⁴ m to 0.229 × 10⁻⁴ m, and the rotational displacement amplitude is reduced from 0.0273 m to 0.0117 m, which effectively suppresses the vibration of the mill and improves the stability of the rolling process. Full article

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19 pages, 4693 KiB

Open AccessArticle

Effect of Nickel Impurities in Pyrite on Catalytic Degradation of Thiosulfate

by Xuecong Qin, Tao Zhang, Wenhua Qin and Hongbo Zhang

Metals 2024, 14(11), 1256; https://doi.org/10.3390/met14111256 - 5 Nov 2024

The effects of nickel content in nickel-bearing pyrite on photocatalytic properties, light absorption properties, and oxidative decomposition of thiosulfate were studied. The leaching experiments show that the consumption of thiosulfate in the Cu²⁺-ethylenediamine (en)-S₂O₃²⁻ system increases with [...] Read more.

The effects of nickel content in nickel-bearing pyrite on photocatalytic properties, light absorption properties, and oxidative decomposition of thiosulfate were studied. The leaching experiments show that the consumption of thiosulfate in the Cu²⁺-ethylenediamine (en)-S₂O₃²⁻ system increases with an increase in nickel content in nickel-bearing pyrite. The consumption of Cu(en)₂²⁺ initially increases and then decreases with an increase in leaching time. There is a clear correlation between the change trend in its consumption and the doping amount of nickel in pyrite. The XPS results show that in the Cu²⁺-ethylenediamine (en)-S₂O₃²⁻ leaching gold system (temperature 25 °C, time 35 h, solution: 0.1 mol/L S₂O₃²⁻, 5 mmol/L Cu(en)₂²⁺, 200 mL solution), the nickel of pyrite-containing nickel can be transferred to the leaching solution and becomes nickel ion. In this leaching system, Cu(II), which was originally complexed with en, is reduced to Cu(I) in a short time. The consumption of Cu(en)₂²⁺ increased rapidly in the 5 h period and then decreased gradually after 5 h. The results showed that the presence of free Ni²⁺ in the solution facilitated the conversion of bivalent copper ions to monovalent copper ions. Free Ni²⁺ ions can compete with Cu²⁺ ions for en ligands. When ethylenediamine complexes with Ni²⁺, the decomposition of Cu(en)₂²⁺ into Cu(en)⁺ and en occurs more rapidly. And the en, which was originally to be oxidized with Cu(en)⁺ to form Cu(en)₂²⁺, forms Ni(en)₂²⁺. As a result, the concentration of Cu(en)₂²⁺ continues to decrease in a short period of time. Full article

(This article belongs to the Special Issue Advances in Mineral Processing and Hydrometallurgy—3rd Edition)

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12 pages, 3428 KiB

Open AccessArticle

Kinetic Analysis of Molten Oxide Reduction Using Bottom-Blown Hydrogen Injection

by Lijin Lu, Feng Wang, Haifeng Wang, Jian Qiu and Xiaodong Ping

Metals 2024, 14(11), 1255; https://doi.org/10.3390/met14111255 - 5 Nov 2024

Hydrogen-based smelting reduction has received widespread attention as an important technology for realizing low-carbon development in hydrogen metallurgy. In this study, the thermodynamics of smelting reduction was firstly analyzed by using FactSage 8.1 thermodynamic software, on the basis of which smelting reduction experiments [...] Read more.

Hydrogen-based smelting reduction has received widespread attention as an important technology for realizing low-carbon development in hydrogen metallurgy. In this study, the thermodynamics of smelting reduction was firstly analyzed by using FactSage 8.1 thermodynamic software, on the basis of which smelting reduction experiments of iron oxides by using bottom-blown hydrogen were carried out. The experiments used oxidized pellets as experimental materials, and the effects of the reduction process were analyzed in terms of the reduction temperature, the reduction time, and the hydrogen flow rate. The experimental results show that under the experimental conditions of a temperature of 1550 °C and a hydrogen flow rate of 0.2 Nm³/h, the reduction rate of iron oxides in the process of reducing iron oxides by hydrogen is significantly faster in the first 10 min than after 10 min. The hydrogen utilization rate reached a maximum of 41.87%, then decreased continuously and finally maintained at about 20%. Using the method of model fitting, it was found that the hydrogen-based molten reduction conformed to the phase boundary reaction model (

G (α) = {1 - (1 - α)}^{1 / 2}

), the corresponding mechanism function is

f (α) = {2 (1 - α)}^{1 / 2}

, where α stands for the reduction conversion, and the reaction rate constant

k (T)

is 2.37 × 10⁻⁴ s⁻¹ under the experimental conditions. Full article

(This article belongs to the Special Issue Advanced Metal Smelting Technology and Prospects)

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11 pages, 7142 KiB

Open AccessArticle

Growth of Surface Oxide Layers on Dendritic Cu Particles by Wet Treatment and Enhancement of Sinter-Bondability by Using Cu Paste Containing the Particles

by Horyun Kim and Jong-Hyun Lee

Metals 2024, 14(11), 1254; https://doi.org/10.3390/met14111254 - 5 Nov 2024

Pastes were prepared using dendritic Cu particles as fillers, and a compression die attachment process was implemented to establish a pure Cu joint using low-cost materials and high-speed sinter bonding. We aimed to grow an oxidation layer on the particle surface to improve [...] Read more.

Pastes were prepared using dendritic Cu particles as fillers, and a compression die attachment process was implemented to establish a pure Cu joint using low-cost materials and high-speed sinter bonding. We aimed to grow an oxidation layer on the particle surface to improve sinter-bondability. Because the growth of the oxidation layer by general thermal oxidation methods makes it difficult to use as a filler owing to agglomeration between particles, we induced oxidation growth by wet surface treatment. Consequently, when the oxidation layer was appropriately grown by surface treatment using an acetic acid–ethanol solution, we obtained an improved joint strength, approximately 2.8 times higher than the existing excellent result based on a bonding time of 10 s. The joint formed in just 10 s at 300 °C in the air under 10 MPa compression showed a shear strength of 28.4 MPa. When the bonding time was increased to 60 s, the joint exhibited a higher strength (35.1 MPa) and a very dense microstructure without voids. These results were attributed to the acceleration of sintering by the in situ formation of more Cu nanoparticles, which effectively reduced the increased oxide layers in the particles using a reducing solvent. Full article

(This article belongs to the Special Issue Advances in Powder Metallurgy of Light Alloys)

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