Metals

16 pages, 2685 KiB

Open AccessArticle

Enhanced Recovery of Lithium and Cobalt from Spent Lithium-Ion Batteries Using Ultrasound-Assisted Deep Eutectic Solvent Leaching

by Tlek Ketegenov, Kaster Kamunur, Lyazzat Mussapyrova, Aisulu Batkal and Rashid Nadirov

Metals 2024, 14(9), 1052; https://doi.org/10.3390/met14091052 (registering DOI) - 14 Sep 2024

Abstract

This study investigates the ultrasound-assisted leaching of Li and Co from spent batteries using a deep eutectic solvent (DES) composed of polyethylene glycol and thiourea. The synergistic effect of ultrasound and DESs was explored to enhance the efficiency of Li and Co recovery. [...] Read more.

This study investigates the ultrasound-assisted leaching of Li and Co from spent batteries using a deep eutectic solvent (DES) composed of polyethylene glycol and thiourea. The synergistic effect of ultrasound and DESs was explored to enhance the efficiency of Li and Co recovery. The experimental results demonstrated that ultrasound significantly accelerates the leaching process, achieving up to four times higher recovery rates compared to traditional methods. Optimal leaching conditions were identified at a solid-to-liquid ratio of 0.02 g/g, a temperature of 160 °C, and periodic ultrasound exposure. Under these conditions, the leaching efficiency reached 74% for Li and 71% for Co within 24 h. A kinetic analysis revealed that the ultrasound application shifts the rate-limiting step from a mixed control of mass transfer and chemical reactions to predominantly chemical reaction control, reducing the activation energy by approximately 27%. Full article

(This article belongs to the Section Extractive Metallurgy)

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21 pages, 4955 KiB

Open AccessArticle

Efficient Phase Segmentation of Light-Optical Microscopy Images of Highly Complex Microstructures Using a Correlative Approach in Combination with Deep Learning Techniques

by Björn-Ivo Bachmann, Martin Müller, Marie Stiefel, Dominik Britz, Thorsten Staudt and Frank Mücklich

Metals 2024, 14(9), 1051; https://doi.org/10.3390/met14091051 (registering DOI) - 14 Sep 2024

Abstract

Reliable microstructure characterization is essential for establishing process–microstructure–property links and effective quality control. Traditional manual microstructure analysis often struggles with objectivity, reproducibility, and scalability, particularly in complex materials. Machine learning methods offer a promising alternative but are hindered by the challenge of assigning [...] Read more.

Reliable microstructure characterization is essential for establishing process–microstructure–property links and effective quality control. Traditional manual microstructure analysis often struggles with objectivity, reproducibility, and scalability, particularly in complex materials. Machine learning methods offer a promising alternative but are hindered by the challenge of assigning an accurate and consistent ground truth, especially for complex microstructures. This paper introduces a methodology that uses correlative microscopy—combining light optical microscopy, scanning electron microscopy, and electron backscatter diffraction (EBSD)—to create objective, reproducible pixel-by-pixel annotations for ML training. In a semi-automated manner, EBSD-based annotations are employed to generate an objective ground truth mask for training a semantic segmentation model for quantifying simple light optical micrographs. The training masks are directly derived from raw EBSD data using modern deep learning methods. By using EBSD-based annotations, which incorporate crystallographic and misorientation data, the correctness and objectivity of the training mask creation can be assured. The final approach is capable of reproducibly and objectively differentiating bainite and martensite in optical micrographs of complex quenched steels. Through the reduction in the microstructural evaluation to light optical micrographs as the simplest and most widely used method, this way of quantifying microstructures is characterized by high efficiency as well as good scalability. Full article

(This article belongs to the Special Issue Machine Learning Models in Metals)

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15 pages, 9600 KiB

Open AccessArticle

The Influence of the Combined Addition of La–Ce Mixed Rare Earths and Sr on the Microstructure and Mechanical Properties of AlSi10MnMg Alloy

by Yu Liu, Zhichao Yu, Man Zhang, Qisheng Feng, Dong Zhang, Pengyue Gao and Chonghe Li

Metals 2024, 14(9), 1050; https://doi.org/10.3390/met14091050 (registering DOI) - 14 Sep 2024

Abstract

This study investigated the effect of adding La–Ce mixed rare earths and Sr on the microstructure and mechanical properties of AlSi10MnMg alloy. The experiment utilized different combinations of modifiers, including single La–Ce rare earths, single Sr, and the combined addition of La–Ce mixed [...] Read more.

This study investigated the effect of adding La–Ce mixed rare earths and Sr on the microstructure and mechanical properties of AlSi10MnMg alloy. The experiment utilized different combinations of modifiers, including single La–Ce rare earths, single Sr, and the combined addition of La–Ce mixed rare earths and Sr. This study compared their effects on grain refinement, the modification of the α-Al phase and eutectic silicon phase, and tensile properties and hardness. The results showed that the combined modification of Sr and mixed rare earth elements significantly refined the grains, optimized the morphology of the α-Al phase and eutectic silicon phase, and improved the overall mechanical properties of the aluminum alloy. Under the combined modification, the addition of 0.02 wt.% Sr and 0.1 wt.% RE (La–Ce mixed rare earths) exhibited the most pronounced refining effect. The secondary dendrite arm spacing (SDAS) was reduced by 59.18%. The eutectic silicon phase transformed from coarse needle-like shapes to fine fibrous or granular forms, with an aspect ratio reduction of 69.39%. Meanwhile, the alloy’s tensile strength and hardness were significantly improved. The tensile strength increased to 240 MPa, achieving an increase of 23.08%; the yield strength increased to 111 MPa, achieving an increase of 18.09%; and the elongation reached 7.3%, achieving an increase of 73.81%. This indicates that the proper addition of Sr and mixed rare earths can significantly optimize the microstructure and enhance the mechanical properties of AlSi10MnMg alloy, providing an effective method for the preparation of high-performance heat-treatment-free aluminum alloys. Full article

(This article belongs to the Special Issue Light Alloy and Its Application (2nd Edition))

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13 pages, 227 KiB

Open AccessEditorial

Advanced Processes in Metallurgical Technologies

by Mariola Saternus and Ladislav Socha

Metals 2024, 14(9), 1049; https://doi.org/10.3390/met14091049 (registering DOI) - 14 Sep 2024

Abstract

The production of metals and their alloys will continue to increase in the coming years, mainly due to the growing demand for these products [...] Full article

(This article belongs to the Topic Advanced Processes in Metallurgical Technologies)

16 pages, 16974 KiB

Open AccessArticle

Effect of Sintering Temperature on the Microstructure and Mechanical and Tribological Properties of Copper Matrix Composite for Brake Pads

by Yajun Zhou, Yongzhen Zhang, Xin Zhang, Jianxiu Liu and Mingxin Wang

Metals 2024, 14(9), 1048; https://doi.org/10.3390/met14091048 (registering DOI) - 14 Sep 2024

Abstract

Copper-based powder metallurgy materials are frequently utilized in fabricating brake pads for high-speed trains. The preparation process involves mixing, ball milling, pressing, and sintering. Among these steps, hot-pressed sintering stands out as a rapid and efficient method that significantly influences the properties and [...] Read more.

Copper-based powder metallurgy materials are frequently utilized in fabricating brake pads for high-speed trains. The preparation process involves mixing, ball milling, pressing, and sintering. Among these steps, hot-pressed sintering stands out as a rapid and efficient method that significantly influences the properties and performance of the products. In this study, four samples (S700/S750/S800/S850) were prepared using hot-pressed sintering at various temperatures, as follows: 700 °C, 750 °C, 800 °C, and 850 °C. The mechanical and physical properties of the four samples were tested, and the microstructure and compositions were investigated using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The findings highlighted the close relationship between sintering temperature and the mechanical and physical properties of the samples, as it impacts the porosity and interfacial bonding of the particles. Notably, Sample S800 demonstrated superior mechanical and thermal conductivity. Furthermore, the coefficient of friction (COF), friction heat, and wear rate of the four samples were also tested under different braking speeds ranging from 150 km/h to 350 km/h. The results indicated that the COFs of the four samples remained relatively stable below 300 km/h but decreased notably above 300 km/h due to heat fading. Sample S800 displayed consistent and high COF under varied braking speeds and exhibited the lowest wear rate. The observed wear mechanisms included abrasive wear and oxidation wear. Additionally, the friction test results underscored the close correspondence of the COF curve of S800 with the standard of the Ministry of Railways of the People’s Republic of China. Full article

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23 pages, 17525 KiB

Open AccessArticle

The Preparation and Properties of a Ni-SiO₂ Superamphiphobic Coating Obtained by Electrodeposition

by Jianguo Liu, Songlin Tong, Shuaihua Wang, Zhiyao Wan, Xiao Xing and Gan Cui

Metals 2024, 14(9), 1047; https://doi.org/10.3390/met14091047 (registering DOI) - 14 Sep 2024

Abstract

Superamphiphobic coatings have shown great potential in many fields such as with their anti-corrosion, high-temperature resistance, self-cleaning, and drag reduction properties. However, due to the poor stability of their coatings, it is difficult to apply them on a large scale. In this paper, [...] Read more.

Superamphiphobic coatings have shown great potential in many fields such as with their anti-corrosion, high-temperature resistance, self-cleaning, and drag reduction properties. However, due to the poor stability of their coatings, it is difficult to apply them on a large scale. In this paper, two kinds of SiO₂ particles and nickel were co-deposited on the surface of steel to construct a micro/nano dual-scale structure by composite electrodeposition. The surface of the coating was then fluorinated with the low-surface-energy material 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (AC-FAS) to prepare a Ni-SiO₂ superamphiphobic coating. The coating has a water contact angle of 159° and an oil contact angle of 151°. The effect of nanoparticle concentration on the wettability and surface morphology of the coating was systematically studied. Comparative experiments revealed that the optimal micro/nanoparticle concentrations were 8 g/L of 20 nm SiO₂ and 2 g/L of 1 μm SiO₂. This preparation method greatly improves the corrosion resistance, wear resistance, chemical stability, and high-temperature resistance of the coating. Full article

(This article belongs to the Special Issue Mechanical Properties and Corrosion Behavior of Metals after Surface Modification)

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13 pages, 6004 KiB

Open AccessArticle

Research on Discrete Clamp Motion Path Control-Based Stretch-Forming Method for Large Surfaces

by Zhen Yang and Qian Tang

Metals 2024, 14(9), 1046; https://doi.org/10.3390/met14091046 (registering DOI) - 14 Sep 2024

Abstract

In this paper, a near-net discrete clamp motion path control (SF-CMPC)-based stretch-forming method is proposed as a solution for the low-cost high-quality machining of highly curved surfaces. In this approach, the clamps are discretized, the motion paths are designed to control deformation distribution [...] Read more.

In this paper, a near-net discrete clamp motion path control (SF-CMPC)-based stretch-forming method is proposed as a solution for the low-cost high-quality machining of highly curved surfaces. In this approach, the clamps are discretized, the motion paths are designed to control deformation distribution and avoid forming defects, the stretch-forming transition zone can be effectively reduced, the material utilization rate can be increased, and the near-net formation of large surfaces can be achieved. To investigate this method’s feasibility, the conventional stretch-forming (SF-C) and SF-CMPC processes are numerically analyzed. The results indicate that, upon increasing the transition zone length via SF-CMPC, the maximum thickness reduction and strain value are reduced by 0.010 mm and 0.0249, respectively, with the dependence of the forming quality on the transition zone length being significantly reduced compared to SF-C. In the formation of surfaces with large curvatures, SF-CMPC’s crack risk is lower than SF-C’s crack risk, with better adaptability. Through controlling the contact process with a die, the sheet metals’ constraint state is improved, the transverse compressive strain can be effectively reduced via friction, and the wrinkling defects can be suppressed. A stretch-forming experiment was carried out on a spherical surface, using self-developed equipment. The feasibility of achieving surfaces’ near-net stretch forming by controlling the clamps’ motion paths was hereby proven. Full article

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12 pages, 4967 KiB

Open AccessArticle

The Influence of Absorbing Coating Material on the Efficiency of Laser Shock Peening

by Elena Gachegova, Denis Davydov, Sergey Mironov, Alexander Kalinenko, Maxim Ozerov, Sergey Zherebtsov and Oleg Plekhov

Metals 2024, 14(9), 1045; https://doi.org/10.3390/met14091045 - 13 Sep 2024

Abstract

Laser shock peening (LSP) is a relatively novel and promising surface hardening method. An absorbing layer, which is needed to protect the specimen surface from undesirable thermal effects caused by laser irradiation, should be considered as one of many varying parameters. The physical [...] Read more.

Laser shock peening (LSP) is a relatively novel and promising surface hardening method. An absorbing layer, which is needed to protect the specimen surface from undesirable thermal effects caused by laser irradiation, should be considered as one of many varying parameters. The physical characteristics of the coating and its adhesion to the specimen surface can significantly influence the result of LSP. In this study, three commonly used absorbing coatings, namely black polyvinylchloride tape with a sticky layer, aluminum foil, and black alkyd paint were used to cover three-millimeter-thick plates of the Ti-6Al-4V titanium alloy with globular or lamellar microstructures. LSP of one side of the plates was carried out with a power density of 10 GW/cm². The hole drilling method was used to evaluate residual stresses. The aluminum foil was found to be the optimal option for LSP of the Ti-6Al-4V titanium alloy. Microstructural investigations carried out using EBSD analysis suggested that no significant reduction in grain size, twinning, or dislocation density growth occurred as a result of LSP irrespective of the initial structure. Full article

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19 pages, 8168 KiB

Open AccessArticle

Extraction of Cobalt and Manganese from Ferromanganese Crusts Using Industrial Metal Waste through Leaching

by Kevin Pérez, Norman Toro, Pedro Robles, Felipe M. Galleguillos Madrid, Edelmira Gálvez, Francisco Javier González, Egidio Marino, Jonathan Castillo, Ingrid Jamett and Pía C. Hernández

Metals 2024, 14(9), 1044; https://doi.org/10.3390/met14091044 - 13 Sep 2024

Abstract

Ferromanganese crusts are mineral resources distributed in the planet’s oceans. These deep-sea minerals stand out for their abundance and diversity of metals, with Mn and Co being the most abundant elements. These minerals are a good alternative to diversify the extraction of elements, [...] Read more.

Ferromanganese crusts are mineral resources distributed in the planet’s oceans. These deep-sea minerals stand out for their abundance and diversity of metals, with Mn and Co being the most abundant elements. These minerals are a good alternative to diversify the extraction of elements, which today are found at low grades on the Earth’s surface. For the co-processing of ferromanganese crusts to recover Co and Mn, there are few studies. These generally worked with the use of a reducing agent, and in many cases previous roasting processes. In the present investigation, two ferromanganese crusts that were collected from two seamounts in the central eastern Atlantic Ocean were characterized. Subsequently, these crusts were leached in an acid-reducing medium, adding steel waste (slag) with 99.73% Fe₃O₄ and 0.27% metallic iron from the steel industry as a reducing agent. Acid-reducing processes have previously been shown to yield high and rapid recoveries of Co and Mn from seabed minerals. However, there is no previous study using smelting slag as a reducing agent for the treatment of ferromanganese crusts. The best results of this research were obtained when working at 60 C, achieving joint extractions of Co and Mn of ~80% and ~40%, respectively, in 10 min. In addition, the process residues were analyzed, and the formation of contaminating elements or the precipitation of Co and Mn species was not observed. Full article

(This article belongs to the Special Issue Flotation and Leaching Processes in Metallurgy (2nd Edition))

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14 pages, 30297 KiB

Open AccessArticle

Production of Spheroidized Micropowders of W-Ni-Fe Pseudo-Alloy Using Plasma Technology

by Andrey Samokhin, Nikolay Alekseev, Aleksey Dorofeev, Andrey Fadeev and Mikhail Sinaiskiy

Metals 2024, 14(9), 1043; https://doi.org/10.3390/met14091043 - 13 Sep 2024

Abstract

The process of obtaining powders from the 5–50 μm fraction of a W-Ni-Fe system consisting of particles with predominantly spherical shapes was investigated. Experimental studies on the plasma–chemical synthesis of a nanopowder composed of WNiFe-90 were carried out in a plasma reactor with [...] Read more.

The process of obtaining powders from the 5–50 μm fraction of a W-Ni-Fe system consisting of particles with predominantly spherical shapes was investigated. Experimental studies on the plasma–chemical synthesis of a nanopowder composed of WNiFe-90 were carried out in a plasma reactor with a confined jet flow. A mixture of tungsten trioxide, nickel oxide, and iron oxide powders interacted with a flow of hydrogen-containing plasma generated in an electric-arc plasma torch. The parameters of the spray-drying process and the composition of a suspension consisting of WNiFe-90 nanoparticles were determined, which provided mechanically strong nanopowder microgranules with a rounded shape and a homogeneous internal structure that contained no cavities. The yield of the granule fraction under 50 μm was 60%. The influence of the process parameters of the plasma treatment of the nanopowder microgranules in the thermal plasma flow on the degree of spheroidization and the microstructure of the obtained particles, seen as their bulk density and fluidity, was established. It was shown that the plasma spheroidization of the microgranules of the W-Ni-Fe system promoted the formation of a submicron internal structure in the obtained spherical particles, which were characterized by an average tungsten grain size of 0.7 μm. Full article

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12 pages, 5308 KiB

Open AccessArticle

Achieving Superior Ductility at High Strain Rate in a 1.5 GPa Ultrahigh-Strength Steel without Obvious Transformation-Induced Plasticity Effect

by Yao Lu, Tianxing Ma, Zhiyuan Liang and Li Liu

Metals 2024, 14(9), 1042; https://doi.org/10.3390/met14091042 - 13 Sep 2024

Abstract

The development of ultrahigh-strength steels with good ductility is crucial for improving the crashworthiness of automobiles. In the present work, the mechanical responses and deformation behaviors of 1.5 GPa ultrahigh-strength steel were systematically investigated over a wide range of strain rates, from 10 [...] Read more.

The development of ultrahigh-strength steels with good ductility is crucial for improving the crashworthiness of automobiles. In the present work, the mechanical responses and deformation behaviors of 1.5 GPa ultrahigh-strength steel were systematically investigated over a wide range of strain rates, from 10⁻³ s⁻¹ to 10³ s⁻¹. The yield strength and tensile elongation at quasi-static strain rate (10⁻³ s⁻¹) were 1548 MPa and 20%, respectively. The yield strength increased to 1930 MPa at an extremely high strain rate (10³ s⁻¹), and the steel maintained excellent ductility, with values as high as 17%. It was found that the prevailing of the transformation-induced plasticity (TRIP) effect at quasi-static condition resulted in the formation of fresh martensite. This produced strong hetero-deformation-induced (HDI) stress and strain partitioning, contributing to the enhancement of strain hardening. The TRIP effect is remarkably suppressed under high strain rates, and thus the retained austenite with excellent deformation ability sustains the subsequent deformation, leading to superior ductility when the TRIP effect and HDI strengthening are retarded. Ultrahigh-strength steel with great strength–ductility combination over a wide range of strain rates has great potential in improving component performance while reducing vehicle weight. Full article

(This article belongs to the Special Issue Physical Metallurgy of Steel)

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Initial microstructure of the investigated steel. (a) XRD patterns of the D&P sample. (b) Three-dimensional EBSD phase map showing the heterogeneous multiphase microstructure. (c) The magnified phase map and band contrast map taken from the normal direction of steels after partitioning treatment. The white arrows correspond to the microstructure features of γ, and white circles represent the microstructure features of α’ and α. Full article ">Figure 2
(a) The engineering stress–strain curves of the D&P steel deformed at various strain rates and (b) the corresponding strain hardening rate curves. (c) Ashby map showing the yield strength versus tensile elongation in comparison with other reported structural materials deformed at high strain rate (103 s−1). Full article ">Figure 3
EBSD phase maps and corresponding XRD patterns of the ultrahigh-strength steel deformed to various strains at a strain rate of (a–c) 10−3 s−1, (d–f) 1 s−1 and (g,h) 103 s−1. (i) The evolution of austenite fraction with a wide strain rate range as a function of tensile strain. Full article ">Figure 4
The loading–unloading–reloading tests and the contribution of HDI strengthening to the present D&P steel deformed at 10−3 s−1 and 10−1 s−1. (a) Tensile LUR true stress–strain curves. (b) Schematic of the method for calculating back stress and effective stress. The green dashed lines represent the tangent lines of unloading and reloading curves. The evolution of back stress and effective stress as a function of tensile strain obtained at strain rates of (c) 10−3 s−1 and (d) 10−1 s−1, respectively. Full article ">Figure 5
Evolution of microstructure for the present steel loaded at strain rate of 10−3 s−1 and 103 s−1. Full article ">

12 pages, 7802 KiB

Open AccessArticle

Influence of Printing Strategies on the Microstructure and Mechanical Properties of Additively Manufactured Alloy 625 Using Directed Energy Deposition (DED-LB-p)

by Florian Scherm, Haneen Daoud and Uwe Glatzel

Metals 2024, 14(9), 1041; https://doi.org/10.3390/met14091041 - 13 Sep 2024

Abstract

Directed energy deposition (DED-LB-p) is used for the production of large components due to the high deposition rates. The large number of process parameters and printing strategies makes it difficult to optimize this process to achieve the optimal properties. Intensive post-processing is still [...] Read more.

Directed energy deposition (DED-LB-p) is used for the production of large components due to the high deposition rates. The large number of process parameters and printing strategies makes it difficult to optimize this process to achieve the optimal properties. Intensive post-processing is still the main obstacle to the widespread use of this process. In this work, the influence of different printing strategies and process parameters on the microstructural and tensile mechanical performance at room temperature is investigated. The porosity is measured in both printing directions. The grain orientation and size are analyzed by EBSD. A very low porosity of less than 0.4% is found in all the printed samples. The samples printed with the optimized offset printing strategy show a significant improvement in tensile strength of 1000 MPa without heat treatment compared to the other processing routes. Full article

(This article belongs to the Special Issue Laser Processing Technology and Principles of Metal Materials)

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12 pages, 41376 KiB

Open AccessArticle

Study on the Optimization of the Tensile Properties of an Al-Li Alloy Friction Stir-Welding T-Joint

by Yu Qiu, Yuansong Zeng, Qiang Meng, Wei Guan, Jihong Dong, Huaxia Zhao, Lei Cui, Xuepiao Bai and Mingtao Wang

Metals 2024, 14(9), 1040; https://doi.org/10.3390/met14091040 - 13 Sep 2024

Abstract

The softening of aluminum–lithium alloy welded joints generally leads to a reduction in mechanical properties. In this study, a piece of 2A97-T3 aluminum–lithium alloy with a thickness of 2.8 mm was selected as the test material, and the tool and process used for [...] Read more.

The softening of aluminum–lithium alloy welded joints generally leads to a reduction in mechanical properties. In this study, a piece of 2A97-T3 aluminum–lithium alloy with a thickness of 2.8 mm was selected as the test material, and the tool and process used for wire-filled stationary shoulder friction stir welding (SSFSW) were developed. By increasing the bearing area of the softening zone, an equal-strength T-joint was manufactured. Good weld formation was obtained when the rotation speed was set to 2000 rpm and the welding speed ranged from 100 to 120 mm/min. The thickness of the softening zone was controlled by adjusting the reserved gap between the shoulder and the workpiece. The softening mechanism of the weld joint was revealed. The softening was attributed to the coarsening of the main precipitated phases (T1 and θ′ phases) in the heat-affected zone (HAZ) and the dissolution of precipitated phases in the thermo-mechanically affected zone (TMAZ). Grain refinement in the nugget zone (NZ) led to a certain fine-grained strengthening effect, although the precipitated phase was almost completely dissolved. Due to the thermal effect of second-pass welding, the hardness value of the NZ and HAZ in the center of the skin further decreased, and the minimum hardness was approximately 70% that of the base material. Tensile testing results indicated that the softening effect was largely offset by the increased bearing area of the softening zone, resulting in the successful welding of high-strength Al-Li alloy T-joints with equal strength. The strength coefficient was found to be 0.977. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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37 pages, 1078 KiB

Open AccessReview

Review of the Use of Metals in Biomedical Applications: Biocompatibility, Additive Manufacturing Technologies, and Standards and Regulations

by Leila Ladani and Michael Palmieri

Metals 2024, 14(9), 1039; https://doi.org/10.3390/met14091039 - 12 Sep 2024

Abstract

Advanced manufacturing techniques such as Additive Manufacturing (AM) have grown rapidly in major industries such as aerospace, automotive, and biomedical device manufacturing. Biomedical industry has benefitted immensely from AM because of its flexibility in design and its rapid production cycle. Powder bed processes [...] Read more.

Advanced manufacturing techniques such as Additive Manufacturing (AM) have grown rapidly in major industries such as aerospace, automotive, and biomedical device manufacturing. Biomedical industry has benefitted immensely from AM because of its flexibility in design and its rapid production cycle. Powder bed processes are the major production technique for metal-based AM implants. This paper serves as a comprehensive review on the research efforts being made using AM to develop new patient centered medical devices. This review focuses on AM of the most common metals for biomedical applications, Magnesium alloys, Cobalt-Chromium alloys, pure Titanium, Titanium alloys. Several different aspects are discussed including biocompatibility and osseointegration, application of specific metals in different types of implants, their advantages and disadvantages, mechanical properties in comparison to bone, and their production technologies. Regulatory and quality assurance hurdles that are facing new innovations made using AM are discussed. Full article

(This article belongs to the Special Issue Optimization of Metal Additive Manufacturing Processes (2nd Edition))

11 pages, 4718 KiB

Open AccessArticle

Ultrafast Hydrogen Production via Hydrolysis of MgH₂-NaH Composite

by Zhao Zhang, Zhenji Li, Wei Zhao, Yushan Zhang, Chong Peng, Changcheng Liu and Li Guo

Metals 2024, 14(9), 1038; https://doi.org/10.3390/met14091038 - 12 Sep 2024

Abstract

Magnesium hydride (MgH₂) has attracted considerable interest due to a number of favourable characteristics for hydrogen production via hydrolysis. In this study, MgH₂-NaH composites with varying composition ratios were prepared by ball milling for different durations. The hydrogen production [...] Read more.

Magnesium hydride (MgH₂) has attracted considerable interest due to a number of favourable characteristics for hydrogen production via hydrolysis. In this study, MgH₂-NaH composites with varying composition ratios were prepared by ball milling for different durations. The hydrogen production performances and enhancement mechanisms were subjected to meticulous investigation. The results revealed that the hydrogen production rate and kinetic properties of the composites were significantly improved with the rise in NaH content. For the MgH₂-10 wt% NaH composites, the hydrogen production rate exhibited an initial increase followed by a subsequent decrease with the prolongation of ball milling. It is noteworthy that the hydrolysis of the composites in deionised water exhibited a significant improvement in reaction kinetics even after a mere 1 h of ball milling, releasing 1119 mL g⁻¹ of hydrogen in 30 s, with a conversion rate of 69.2%. The highest hydrolysis hydrogen generation rate of the 10 h milled MgH₂-10 wt% NaH composite in deionised water at 30 °C was 1360 mL g⁻¹, with a hydrogen conversion rate of 83.7% and a hydrolysis activation energy of 17.79 kJ mol⁻¹. The notable improvement in the hydrolysis performance of the MgH₂-NaH composite is attributed to the rapid generation of high temperatures at the interface, resulting from the exothermic reaction of sodium hydride hydrolysis. Full article

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

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17 pages, 11437 KiB

Open AccessArticle

Improvement of Tribological Properties and Corrosion Resistance of AISI 4340M Steel by Shot Peening and Plating Technologies

by Seok-Hwan Ahn, Jungsik Kim and Auezhan Amanov

Metals 2024, 14(9), 1037; https://doi.org/10.3390/met14091037 - 12 Sep 2024

Abstract

In this study, shot peening (SP), quenching and tempering (QT) heat treatment, baking heat treatment and Cr-plating technologies were used to enhance the hardness, tribological properties and corrosion resistance of AISI 4340M steel. The purpose of this study is to develop repair process [...] Read more.

In this study, shot peening (SP), quenching and tempering (QT) heat treatment, baking heat treatment and Cr-plating technologies were used to enhance the hardness, tribological properties and corrosion resistance of AISI 4340M steel. The purpose of this study is to develop repair process technology for an overhaul of landing gear applied to the MRO process and establish a quality assurance system. The effects of SP, QT heat treatment, Cr-plating, stripping after Cr-plating and Cr-plating after stripping and re-SP on the tribological properties and corrosion resistance of AISI 4340M steel were investigated, and the obtained results were compared with the base AISI 4340M steel. One of the reasons for stripping after Cr-plating is to find out how many times stripping can be done after Cr-plating. Moreover, it is important to investigate the effect of re-SP after Cr-plating on the tribological properties and corrosion resistance. The tribological properties of the specimens were investigated using a ball-on-disk tribometer at room temperature against AISI 52100 steel for 60 min under dry conditions. The corrosion resistance was investigated using a potentiodynamic polarization test in NaCl 3.5% solution. The results showed that the application of SP, QT heat treatment, Cr-plating, stripping after Cr-plating and Cr-plating after stripping and re-SP had a significant effect on the tribological properties and corrosion resistance of AISI 4340M steel. The effects of SP and Cr-plating post-treatment technologies on the wear and corrosion enhancement and mechanisms were discussed based on the microstructural and surface morphology of worn and corroded surfaces. Full article

(This article belongs to the Special Issue Surface Strengthening and Modification of Metallic Materials)

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13 pages, 2042 KiB

Open AccessArticle

DFT Insights into the Physical Properties of Layered LiMnSe₂ and LiMnTe₂ Compounds

by Abdennour Benmakhlouf, Fares Faid, Nedjmeddine Ghermoul, Kemal Özdoğan, Taoufik Helaimia, Abdelmadjid Bouhemadou and Iosif Galanakis

Metals 2024, 14(9), 1036; https://doi.org/10.3390/met14091036 - 12 Sep 2024

Abstract

Using state-of-the-art first-principles electronic-band-structure calculations alongside density functional theory, we investigated the structural, elastic, electronic, and magnetic properties of LiMnZ₂ (Z = Se, Te) compounds with a trigonal structure. Initially, we determined the equilibrium lattice structure and atomic positions, which aligned well [...] Read more.

Using state-of-the-art first-principles electronic-band-structure calculations alongside density functional theory, we investigated the structural, elastic, electronic, and magnetic properties of LiMnZ₂ (Z = Se, Te) compounds with a trigonal structure. Initially, we determined the equilibrium lattice structure and atomic positions, which aligned well with experimental values. Ferromagnetism was shown to be more favorable than the non-magnetic state. The elastic constants, cohesive energies, and formation energies indicated that the studied compounds were mechanically stable in the experimentally determined trigonal lattice. The analysis of spin-polarized band structures and density of states revealed that both LiMnZ₂ compounds exhibited perfect half-metallic characters. The total spin magnetic moment per formula unit adhered to the Slater–Pauling rule, being exactly 4 μ_Β, mainly concentrated at the Mn atoms due to the strong spin polarization of the Mn d orbitals. We anticipate that our results will prompt further experimental and computational studies for the application of these layered materials in practical devices. Full article

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

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Figure 1
A conventional cell of the LiMnZ2 (Z = Se, Te) trigonal structure. The purple circles represent the Se(Te) atoms, the red circles represent the Li atoms, and the rest represent the Mn atoms. The MnSe(Te)4 tetrahedra were the fundamental building blocks of the LiMnZ2 crystals. The colored arrows denote the cartesian coordinate system. Full article ">Figure 2
For LiMnSe2 (left panel) and LiMnTe2 (right panel), we present the total energy per unit cell as a function of the unit cell volume. We considered for each compound both the ferromagnetic alignment of the Mn spin magnetic moments (FM) and the case where we obliged our atoms to carry no net spin magnetic moments (denoted as non-magnetic, NM). Full article ">Figure 3
Calculated band structure for LiMnSe2 along several high-symmetry axes for both spin-down (left panel) and spin-up (right panel) directions. The dashed line denotes the Fermi level. Full article ">Figure 4
Similar to <a href="#metals-14-01036-f002" class="html-fig">Figure 2</a> for LiMnTe2. Full article ">Figure 5
Calculated spin-projected total and atom-resolved density of states for the two compounds under study (LiMnSe2 in the (left panel) and LiMnTe2 in the (right panel)). The Fermi level, depicted by a vertical dashed line, is adjusted to zero for reference. Note that the scale of the vertical DOS axis is different for the various atoms. Full article ">

13 pages, 5969 KiB

Open AccessArticle

Abnormal Effect of Al on the Phase Stability and Deformation Mechanism of Ti-Zr-Hf-Al Medium-Entropy Alloys

by Penghao Yuan, Lu Wang, Ying Liu and Xidong Hui

Metals 2024, 14(9), 1035; https://doi.org/10.3390/met14091035 - 11 Sep 2024

Abstract

Complex concentrated alloys, including high-entropy alloys (HEAs) and medium-entropy alloys (MEAs), offer another pathway for developing metals with excellent mechanical properties. However, HEAs/MEAs of different structures often suffer from various drawbacks. So, investigations on the effect of phase and microstructure on their properties [...] Read more.

Complex concentrated alloys, including high-entropy alloys (HEAs) and medium-entropy alloys (MEAs), offer another pathway for developing metals with excellent mechanical properties. However, HEAs/MEAs of different structures often suffer from various drawbacks. So, investigations on the effect of phase and microstructure on their properties become necessary. In the present work, we adjust the phase constitution and microstructure by Al addition in a series of (Ti₂ZrHf)_100−xAl_x (x = 12, 14, 16, 18, 20, at.%, named Al_x) MEAs. Different from traditional titanium, Al shows a β-stabilizing effect, and the phase follows the evolution of α′(α)→α″→β + ω + B2 with Al increasing from 12 to 20 at.%, which could not be predicted by the CALPHAD (Calculate Phase Diagrams) method or the Bo-Md diagram because of the complex interactions among composition elements. At a low Al content, the solid solution strengthening of the HCP phase contributes to the extremely high strength with a σ_0.2 of 1528 MPa and σ_b of 1937 MPa for Al14. The appearance of α″ deteriorates the deformation capability with increasing Al content in the Al16 and Al18 MEAs. In the Al20 MEA, Al improves the formations of ordered B2 and metastable β. The phase transformation strengthening, including B2 to BCC and BCC to α″, together with the precipitation strengthening of ω, brings about a high work-hardening ratio (above 5 GPa) and improvements in ductility (6.8% elongation). This work provides guidelines for optimizing the properties of MEAs. Full article

(This article belongs to the Section Entropic Alloys and Meta-Metals)

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15 pages, 23687 KiB

Open AccessArticle

Evaluation of Shear-Punched Surface Layer Damage in Ultrahigh-Strength TRIP-Aided Steels with Bainitic Ferrite and/or Martensite Matrix Structure

by Koh-ichi Sugimoto, Shoya Shioiri, Junya Kobayashi and Tomohiko Hojo

Metals 2024, 14(9), 1034; https://doi.org/10.3390/met14091034 - 11 Sep 2024

Abstract

The damage to the shear-punched surface layers such as strain-hardening, strain-induced martensite transformation, and micro-void initiation behaviors was evaluated in the third-generation low-carbon advanced ultrahigh-strength TRIP-aided bainitic ferrite (TBF), bainitic ferrite–martensite (TBM), and martensite (TM) steels. In addition, the surface layer damage was [...] Read more.

The damage to the shear-punched surface layers such as strain-hardening, strain-induced martensite transformation, and micro-void initiation behaviors was evaluated in the third-generation low-carbon advanced ultrahigh-strength TRIP-aided bainitic ferrite (TBF), bainitic ferrite–martensite (TBM), and martensite (TM) steels. In addition, the surface layer damage was related to (1) the mean normal stress generated during shear-punching and (2) microstructural properties such as the matrix structure, retained austenite characteristics, and second-phase properties. The shear-punched surface layer damage was produced under the mean normal stress between zero and negative in all the steels. The TBM and TM steels achieved relatively small surface layer damage. The small surface layer damage resulted in excellent cold stretch-flangeability, with a high crack-propagation/void-connection resistance on hole expansion. Full article

(This article belongs to the Special Issue Microstructure–Mechanical Property Relationships in High-Strength Steels (2nd Edition))

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