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 & Metallurgical Engineering) / CiteScore - Q1 (Metals and Alloys)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 15 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the second half of 2023).
- 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:
2.9 (2022);
5-Year Impact Factor:
2.9 (2022)
Latest Articles
On the Problem of the Distillation Separation of Secondary Alloys of Magnesium with Zinc and Magnesium with Cadmium
Metals 2024, 14(6), 671; https://doi.org/10.3390/met14060671 - 5 Jun 2024
Abstract
An alternative to the existing method of processing secondary magnesium raw materials by remelting in a salt furnace can be distillation separation into volatile metals (Mg, Zn and Cd), low-volatile metals (Al, Mn and Zr) and rare earth elements. The separation of metals
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An alternative to the existing method of processing secondary magnesium raw materials by remelting in a salt furnace can be distillation separation into volatile metals (Mg, Zn and Cd), low-volatile metals (Al, Mn and Zr) and rare earth elements. The separation of metals may be tracked based on phase diagrams where the field boundaries of the vapor–liquid equilibrium are plotted. Due to the fact that Mg, Zn and Cd have comparable saturated vapor pressures, the possibility of the distillation separation of Mg–Zn and Mg–Cd systems using full state diagrams including the melt–vapor phase transition boundaries were determined in this work. The boundaries of these systems were calculated based on the partial values of saturated vapor, determined by the boiling point method, and presented in the form of temperature–concentration dependencies with the indicated boundaries. The field boundaries were calculated (L + V) at atmospheric pressure (101.33 kPa) and in vacuum (1.33 kPa and 0.7 kPa,) supposing the implementation of the process. The possibility of the separate extraction of zinc and cadmium from magnesium was considered using complete phase diagrams including the boundaries of the melt–steam phase transition. When considering the boundaries of the vapor–liquid equilibrium in the binary systems Mg–Zn and Mg–Cd, it was established that it is impossible to separate metals in one “evaporation–condensation” cycle in a vacuum of 1.33 and 0.7 kPa. The problem is caused by the small size of the fields (L + V) at the temperature, which suggests processes of the re-evaporation of the condensate from the previous distillation stage. The separation of zinc and cadmium from liquid alloys with magnesium under equilibrium conditions requires several repetitions of the condensate distillation process. In non-equilibrium conditions, the real processes will require a larger number of conversions. This implies the expediency of the joint evaporation of magnesium with zinc and cadmium and the use of condensate for additional charging to liquid magnesium, and the remainder of the distillation, where volatile metals such as Al, Mn, Zr and rare earth elements will be concentrated, should be directed to the preparation of ligatures for special magnesium-based alloys.
Full article
(This article belongs to the Special Issue Separation and Purification of Metals (Second Edition))
Open AccessArticle
Surface Growth of Boronize Coatings Studied with Mathematical Models of Diffusion
by
Martín Ortiz-Domínguez, Ángel Jesús Morales-Robles, Oscar Armando Gómez-Vargas and Georgina Moreno-González
Metals 2024, 14(6), 670; https://doi.org/10.3390/met14060670 - 5 Jun 2024
Abstract
The following investigation focused on examining the kinetics of Fe2B coating formation on the surface of ASTM A681 steel during the powder-pack boronizing process. The study measured Fe2B coating thicknesses at various temperatures and exposure times to confirm the
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The following investigation focused on examining the kinetics of Fe2B coating formation on the surface of ASTM A681 steel during the powder-pack boronizing process. The study measured Fe2B coating thicknesses at various temperatures and exposure times to confirm the diffusion-controlled growth mechanism during boronizing. Five distinct mathematical models were devised to determine the boron diffusion coefficients in Fe2B coatings. Understanding the growth kinetics of boronize coatings is imperative as it facilitates the optimization and automation of industrial processes. This ensures the efficient and consistent production of boronize coatings on cutting tools, such as drills and milling cutters, due to their high hardness and wear resistance. The value of the activation energy estimated with five mathematical diffusion models for the Fe2B coating was 209.8 kJ∙mol−1. The X-ray diffraction technique was used to identify the presence of the iron boronize phase. Tribological studies were also performed to evaluate the coefficient of friction (COF) of the boronized (0.256) and untreated (0.781) samples, having a 300% positive effect of the boronize coating on wear resistance. Finally, the models were empirically validated for two supplementary treatment conditions for 1223 K for 3 h and 1273 K for 1.5 h, where the percentage error for both conditions was estimated to be approximately 2.5%.
Full article
Open AccessReview
Review of In Situ Detection and Ex Situ Characterization of Porosity in Laser Powder Bed Fusion Metal Additive Manufacturing
by
Beytullah Aydogan and Kevin Chou
Metals 2024, 14(6), 669; https://doi.org/10.3390/met14060669 - 5 Jun 2024
Abstract
Over the past decade, significant research has focused on detecting abnormalities in metal laser powder bed fusion (L-PBF) additive manufacturing. Effective online monitoring systems are crucial for enhancing process stability, repeatability, and the quality of final components. Therefore, the development of in situ
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Over the past decade, significant research has focused on detecting abnormalities in metal laser powder bed fusion (L-PBF) additive manufacturing. Effective online monitoring systems are crucial for enhancing process stability, repeatability, and the quality of final components. Therefore, the development of in situ detection mechanisms has become essential for metal L-PBF systems, making efficient closed-loop control strategies to adjust process parameters in real time vital. This paper presents an overview of current in situ monitoring systems used in metal L-PBF, complemented by ex situ characterizations. It discusses in situ techniques employed in L-PBF and evaluates the applicability of commercial systems. The review covers optical, thermal, acoustic, and X-ray in situ methods, along with destructive and non-destructive ex situ methods like optical, Archimedes, and X-ray characterization techniques. Each technique is analyzed based on the sensor used for defect detection and the type or size of defects. Optical in situ monitoring primarily identifies large defects from powder bed abnormalities, while thermal methods detect defects as small as 100 µm and keyholes. Thermal in situ detection techniques are notable for their applicability to commercial devices and efficacy in detecting subsurface defects. Computed tomography scanning excels in locating porosity in 3D space with high accuracy. This study also explores the advantages of multi-sensor in situ techniques, such as combining optical and thermal sensors, and concludes by addressing current research needs and potential applications of multi-sensor systems.
Full article
(This article belongs to the Special Issue Advances in Additive Manufacturing Technology of Metals and Alloys)
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Open AccessArticle
Electrochemical Behaviour of an Au-Ge Alloy in an Artificial Saliva and Sweat Solution
by
Gyöngyi Vastag, Peter Majerič, Vojkan Lazić and Rebeka Rudolf
Metals 2024, 14(6), 668; https://doi.org/10.3390/met14060668 - 5 Jun 2024
Abstract
In modern times, more and more different materials (including alloys) are in direct contact with human electrolytes (sweat, saliva, lymph, blood, etc.). One of the most important properties for the use of these materials is therefore their chemical inertness or resistance to corrosion
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In modern times, more and more different materials (including alloys) are in direct contact with human electrolytes (sweat, saliva, lymph, blood, etc.). One of the most important properties for the use of these materials is therefore their chemical inertness or resistance to corrosion when they are in contact with human electrolytes. Consequently, during the development of such new materials, it is necessary to study and understand their basic electrochemical behaviour in a given environment. The purpose of this research was to monitor the electrochemical behaviour of the new Au-Ge alloy in artificial sweat and artificial saliva solutions, depending on the electrolyte composition and exposure time. This new alloy represents a potential material for use in dentistry or for jewellery. The obtained results of the study show that the immersion time and the pH value have a significantly greater influence on the corrosion resistance of the new Au-Ge alloy than the composition of the electrolyte solution. The results of the SEM/EDX analysis additionally confirm the main results of the electrochemical measurements.
Full article
(This article belongs to the Special Issue Feature Papers in Extractive Metallurgy)
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Open AccessReview
Deep Rolling Techniques: A Comprehensive Review of Process Parameters and Impacts on the Material Properties of Commercial Steels
by
Dilifa Jossley Noronha, Sathyashankara Sharma, Raghavendra Prabhu Parkala, Gowri Shankar, Nitesh Kumar and Srinivas Doddapaneni
Metals 2024, 14(6), 667; https://doi.org/10.3390/met14060667 - 4 Jun 2024
Abstract
The proposed review demonstrates the effect of the surface modification process, specifically, deep rolling, on the material surface/near-surface properties of commercial steels. The present research examines the various process parameters involved in deep rolling and their effects on the material properties of AISI
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The proposed review demonstrates the effect of the surface modification process, specifically, deep rolling, on the material surface/near-surface properties of commercial steels. The present research examines the various process parameters involved in deep rolling and their effects on the material properties of AISI 1040 steel. Key parameters such as the rolling force, feed rate, number of passes, and roller geometry are analyzed in detail, considering their influence on residual stress distribution, surface hardness, and microstructural alterations. Additionally, the impact of deep rolling on the fatigue life, wear resistance, and corrosion behavior of AISI 1040 steel is discussed. Engineering components manufactured by AISI 1040 steel can perform better and last longer when deep rolling treatments are optimized with an understanding of how process variables and material responses interact. This review provides critical insights for researchers and practitioners interested in harnessing deep rolling techniques to enhance the mechanical strength and durability of steel components across diverse industrial settings. In summary, the valuable insights provided by this review pave the way for continued advancements in deep rolling techniques, ultimately contributing to the development of more durable, reliable, and high-performance steel components in diverse industrial applications. The establishment of generalized standardizations for the deep rolling process proves unfeasible because of the multitude of controlling parameters and their intricate interactions. Thus, specific optimization studies tailored to the material of interest are imperative for process standardization. The published literature on the characterization of surface and subsurface properties of deep-rolled AISI 1040 steel, as well as process parameter optimization, remains limited. Additionally, numerical, analytical, and statistical studies and the role of ANN are limited compared with experimental work on the deep rolling process.
Full article
(This article belongs to the Special Issue Advances in Metal Rolling Processes)
Open AccessArticle
Study on Fracture Behavior and Toughening Mechanisms of Ultra-High-Strength Pipeline Steel
by
Ba Li, Xiaoshun Zhou, Shujun Jia, Xiaoping Chen, Song Fu, Dongliang Zhao, Haonan Zhang and Jie Guo
Metals 2024, 14(6), 666; https://doi.org/10.3390/met14060666 - 4 Jun 2024
Abstract
In this paper, a series of low-temperature CVN (Charpy V-notch impact test) and DWTT (drop-weight tear test) experiments were carried out to deal with the intensifying contradiction of strength and toughness of ultra-high-strength pipeline steel. The fracture behavior and toughening mechanisms of ultra-high-strength
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In this paper, a series of low-temperature CVN (Charpy V-notch impact test) and DWTT (drop-weight tear test) experiments were carried out to deal with the intensifying contradiction of strength and toughness of ultra-high-strength pipeline steel. The fracture behavior and toughening mechanisms of ultra-high-strength pipeline steel were investigated using scanning electron microscopy, transmission electron microscopy and backscattered electron diffraction systems. The results show that DWTT fractures in ultra-high-strength pipeline steel had a variety of unconventional morphological features compared to CVN fractures, including ridge protrusion in ductile fracture conditions and a large-size fracture platform in brittle fracture conditions. Therefore, DWTT fractures contained more information about the material fracturing process, and could better reflect the actual process of material fracturing. In ultra-high-strength pipeline steel, fine-grained granular bainite caused cracks to undergo large deflections or frequent small transitions, which consumed additional energy and improved toughness. In contrast, large-sized granular bainite, which consisted of low-angle grain boundaries, did not effectively prevent crack propagation when it encountered cracks, which was not conducive to improved toughness. Moreover, the M/A constituents in large-sized granular bainite aggregated, cracked, or fell off, which could easily lead to the formation of microcracks and was also detrimental to toughening.
Full article
(This article belongs to the Special Issue Design, Preparation and Properties of High Performance Steels)
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Open AccessArticle
Microstructure and Pore Characteristics of a Double-Layered Pore Structure Powder Filter Fabricated by the WPS Process
by
Min-Jeong Lee, Hyeon-Ju Kim, Du-Hong Kang, Jung Woo Lee and Jung-Yeul Yun
Metals 2024, 14(6), 665; https://doi.org/10.3390/met14060665 - 4 Jun 2024
Abstract
In order to supply high-purity process gas in the semiconductor manufacturing process, a gas filter is used to remove particles that may be contained in the gas. However, because the gas filters currently in use have simple pore structures, there is a need
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In order to supply high-purity process gas in the semiconductor manufacturing process, a gas filter is used to remove particles that may be contained in the gas. However, because the gas filters currently in use have simple pore structures, there is a need to increase filtration efficiency through the development of filters with complex pore structures. In this study, a metal powder filter with double-layered pores was manufactured using a Wet Powder Spraying process (WPS) to increase the filtering efficiency of gas filters used in semiconductor manufacturing. The effects of the mixing ratio of spherical-shape and flake-shape powders and the rolling process on the filter’s characteristics were investigated. The filter’s performance, microstructure, and surface roughness were evaluated by measuring porosity and gas permeability. The results showed that as the ratio of flake-shaped powder decreased, the thickness of the coating layer and the porosity of the filter decreased. Additionally, it was observed that as the rolling process progressed, the non-uniform pore structure was oriented parallel to the cross-section of the filter regardless of the mixing ratio. Measurements found that the gas permeability of the uncoated filter support was the highest, and that gas permeability decreased as the proportion of spherical powder increased regardless of the average particle size of the mixed powder. Lower gas permeability was observed in rolled samples. A filtration efficiency of LRV 3 or higher was confirmed.
Full article
(This article belongs to the Special Issue Advances in Powder Metallurgy of Light Alloys)
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Open AccessArticle
Influence of Process Parameters on the Mechanical Properties and Corrosion Resistance of Dissimilar Friction Stir Welded Joints of AA2024-O and AA6061-O Aluminum Alloys
by
Roosvel Soto-Diaz, Anderson Sandoval-Amador, José Escorcia-Gutierrez and Jimy Unfried-Silgado
Metals 2024, 14(6), 664; https://doi.org/10.3390/met14060664 - 3 Jun 2024
Abstract
The influence of the process parameters, traverse, and rotational speeds of dissimilar friction stir welded joints of AA2024-O and AA6061-O aluminum alloys on the corrosion resistance was evaluated. Potentiodynamic tests using a 3.5% NaCl solution, open circuit potential, and polarization curves showed the
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The influence of the process parameters, traverse, and rotational speeds of dissimilar friction stir welded joints of AA2024-O and AA6061-O aluminum alloys on the corrosion resistance was evaluated. Potentiodynamic tests using a 3.5% NaCl solution, open circuit potential, and polarization curves showed the corrosion behavior for the different welding parameters. These data were correlated with those obtained by mechanical tests (microhardness, tensile, and fracture analysis) and microstructure analysis by optical and scanning electron microscopy. It was observed that the combined effect of the parameters influenced the variation of corrosion resistance. This was evidenced mainly by the improvement of corrosion resistance at 1200 rpm–65 mm·min−1, which was related to the tendency of grain size and heat input presented. The corrosive attacks on the welded joints presented greater affectations in the presence of base material 1 (AA6061-O) with higher metallic dissolution. Corrosion attacks abovementioned were presented in different forms, such as pitting, localized, and selective, and they were observed by scanning electron microscopy. Finally, in corrosive and mechanical terms, the best performing condition was 1200 rpm and 65 mm·min−1 compared to the low parameter of 840 rpm and 45 mm·min−1.
Full article
(This article belongs to the Section Welding and Joining)
Open AccessArticle
Physical Simulation of Mold Steels Repaired by Laser Beam Fusion Deposition
by
Joel de Jesus, José A. M. Ferreira, Carlos Capela, José D. M. da Costa and Luís Borrego
Metals 2024, 14(6), 663; https://doi.org/10.3390/met14060663 - 3 Jun 2024
Abstract
In the present work, a study of the fatigue strength of two materials widely used in the production of molds, namely, the AISI P20 and AISI H13 steels, is presented. The tests were performed at a constant amplitude with a stress ratio of
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In the present work, a study of the fatigue strength of two materials widely used in the production of molds, namely, the AISI P20 and AISI H13 steels, is presented. The tests were performed at a constant amplitude with a stress ratio of R = 0 using samples where U-shaped notches were filled with laser beam fusion deposition. Three different sets of deposition parameters for each material were analyzed. Fatigue strength results are presented as S-N curves obtained for filled and non-filled materials. In addition to the assessment of the fatigue strength, metallography, hardness, and the fracture surface of the specimens tested were also evaluated. In general, a high number of metallurgic defects was detected, and consequently, a decrease in the mechanical properties of the materials was observed, especially the fatigue strength. However, the parameter optimization of the repairing laser process produced repaired zones with good metallurgical quality, leading to higher fatigue strength in both of the high-strength steels analyzed.
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(This article belongs to the Special Issue Fatigue Assessment of Metals)
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Open AccessFeature PaperArticle
Effects of PVD CrAlN/(CrAlB)N/CrAlN Coating on Pin–Disc Friction Properties of Ti2AlNb Alloys Compared to WC/Co Carbide at Evaluated Temperatures
by
Jinfu Zhao, Lirui Zheng, Wenqian Li, Zhanqiang Liu, Liangliang Li, Bing Wang, Yukui Cai, Xiaoping Ren and Xiaoliang Liang
Metals 2024, 14(6), 662; https://doi.org/10.3390/met14060662 - 2 Jun 2024
Abstract
Physical vapor deposition (PVD) coatings could affect the friction performance at the contact interface between Ti2AlNb alloy parts and tool couples. Suitable coating types could improve the friction properties of Ti2AlNb alloy while in contact with WC/Co carbide. In
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Physical vapor deposition (PVD) coatings could affect the friction performance at the contact interface between Ti2AlNb alloy parts and tool couples. Suitable coating types could improve the friction properties of Ti2AlNb alloy while in contact with WC/Co carbide. In this study, the linear reciprocating pin–disc friction tests between the Ti2AlNb alloy and the WC/Co carbide tool couple, with the sole variation of the PVD CrAlN/(CrAlB)N/CrAlN coating were conducted within the temperature range of 25–600 °C. The antifriction properties of the Ti2AlNb alloy were estimated using the time-varied friction coefficients, the alloy wear rate, worn surface topography, worn surface element, and wear mechanism analysis. The results showed that the PVD CrAlN/(CrAlB)N/CrAlN coating could decrease the average friction coefficient and alloy wear rate compared to the uncoated WC/Co carbide couple. The apparent adhesive wear and abrasive wear of the Ti2AlNb alloy could be improved due to the PVD coating at evaluated temperatures. The PVD CrAlN/(CrAlB)N/CrAlN coating could be utilized to improve the antifriction properties of the Ti2AlNb alloy, which may be deposited on the cutting tool to improve the machining performance of Ti2AlNb alloys in future aerospace machining industry.
Full article
(This article belongs to the Special Issue Microstructure and Tribological Properties of High Entropy Alloy/Funtional Coatings)
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Open AccessArticle
The Effect of Heat Treatment on the Microstructure and Mechanical Properties of Powder Metallurgy Ti-48Al Alloy
by
Mengjie Yan, Hongtao Zhang, Fang Yang, Yunwei Gui, Zhijie Han and Huadong Fu
Metals 2024, 14(6), 661; https://doi.org/10.3390/met14060661 - 1 Jun 2024
Abstract
Heat treatment is the critical step in achieving a refined microstructure and enhanced mechanical properties of TiAl-based alloys. This study investigated the influence of heat treatment temperature, cooling method, and heat treatment time on the microstructure and mechanical properties of an extruded powder
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Heat treatment is the critical step in achieving a refined microstructure and enhanced mechanical properties of TiAl-based alloys. This study investigated the influence of heat treatment temperature, cooling method, and heat treatment time on the microstructure and mechanical properties of an extruded powder metallurgy Ti-48Al alloy, and achieved the control of fully lamellar fine microstructures and the enhancement of performance through a simple heat treatment, rather than the traditional approach of homogenization followed by heat treatment. The results indicate that the heat treatment temperature determines the type of microstructure, while the cooling rate dictates the lamellar width. As the heat treatment temperature was increased from the two-phase region to the α single-phase region, the microstructure transitioned from duplex to near lamellar, and the alloy strength initially increased and then decreased, influenced by both the lamellar colony ratio and grain size. A rapid cooling rate (water quenching) induces a non-diffusive massive phase transformation, whereas a slow cooling rate (air cooling) gradually forms α2/γ lamellar colonies. Therefore, a suitable heat treatment regime for the powder metallurgy Ti-48Al alloy was determined to be 1340 °C/5 min/air cooling. The microstructure of the alloy was near lamellar, consisting of lamellar colonies approximately 50 μm and a small number of γ equiaxed grains of about 10 μm. Subsequently, the alloy exhibited a room temperature tensile strength of 784 MPa and a yield strength of 763 MPa, representing improvements of 17.0% and 38.7% over the extruded alloy, respectively. This research provides a reference for establishing a heat treatment process for powder metallurgy TiAl alloys.
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(This article belongs to the Special Issue Advances in Powder Metallurgy of Light Alloys)
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Open AccessArticle
Effect of Printing Orientation on the Mechanical Properties of 3D-Printed Cu–10Sn Alloys by Laser Powder Bed Fusion Technology
by
Peng Yang, Dingyong He, Xingye Guo, Sheng Lu, Shujin Chen, Fanmin Shang, Dubovyy Oleksandr and Liangyu Chen
Metals 2024, 14(6), 660; https://doi.org/10.3390/met14060660 - 1 Jun 2024
Abstract
This article focuses on investigating the effect of printing direction on the mechanical properties of Cu–10Sn alloys prepared by laser powder bed fusion (LPBF) technology. Specimens with different forming angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) were fabricated using LPBF technology,
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This article focuses on investigating the effect of printing direction on the mechanical properties of Cu–10Sn alloys prepared by laser powder bed fusion (LPBF) technology. Specimens with different forming angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) were fabricated using LPBF technology, and their mechanical properties were systematically tested. During the testing process, we used an Instron 5985 electronic universal material testing machine to accurately evaluate the mechanical properties of the material at a constant strain rate of 10−3/s. The experimental results showed that the mechanical properties of the specimens were the best when the test direction was perpendicular to the growth direction (i.e., the 0° direction). As the angle between the test direction and the growth direction increased, the mechanical properties of the material exhibited a trend of first decreasing, then increasing, and then decreasing again, which was consistent with the direction of the microtexture of the specimens. The root cause of this trend lies in the significant change in the stress direction borne by the columnar crystals under different load directions. Specifically, as the load direction gradually transitions from being parallel to the columnar crystals to perpendicular to them, the stress direction of the columnar crystals also shifts from the radial direction to the axial direction. Due to the differences in the number and strength of grain boundaries in different stress directions, this directly leads to changes in mechanical properties. In particular, when the specimen is loaded in the radial direction of the columnar crystals, the grain boundary density is higher, and these grain boundaries provide greater resistance during dislocation migration, thus significantly hindering tensile deformation and enabling the material to exhibit superior tensile properties. Among all the tested angles, the laser powder bed fusion specimen with a forming angle of 0° exhibited the best mechanical properties, with a tensile strength of 723 MPa, a yield strength of 386 MPa, and an elongation of 33%. In contrast, the specimen with a forming angle of 90° performed the worst in terms of tensile properties. These findings provide important insights for us to deeply understand the mechanical properties of Cu–10Sn alloys prepared by LPBF.
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(This article belongs to the Topic Laser Processing of Metallic Materials)
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Open AccessArticle
Comparison of Nitriding Behavior for Austenitic Stainless Steel 316Ti and Super Austenitic Stainless Steel 904L
by
Stephan Mändl and Darina Manova
Metals 2024, 14(6), 659; https://doi.org/10.3390/met14060659 - 1 Jun 2024
Abstract
In situ X-ray diffraction (XRD) was used to compare nitrogen low-energy ion implantation (LEII) into austenitic stainless steel 316Ti and super austenitic stainless steel 904L. While the diffusion and layer growth were very similar, as derived from the decreasing intensity of the substrate
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In situ X-ray diffraction (XRD) was used to compare nitrogen low-energy ion implantation (LEII) into austenitic stainless steel 316Ti and super austenitic stainless steel 904L. While the diffusion and layer growth were very similar, as derived from the decreasing intensity of the substrate reflection, strong variations in the observed lattice expansion—as a function of orientation, the steel alloy, and nitriding temperature—were observed. Nevertheless, a similar resulting nitrogen content was measured using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Furthermore, for some conditions, the formation of a double layer with two distinct lattice expansions was observed, especially for steel 904L. Regarding the stability of expanded austenite, 316Ti had already decayed in CrN during nitriding at 500 °C, while no such effect was observed for 904L. Thus, the alloy composition has a strong influence only on the lattice expansion and the stability of expanded austenite—but not the diffusion and nitrogen content.
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(This article belongs to the Special Issue Advances in Low-Temperature Nitriding and Carburizing of Stainless Steels and Metallic Materials: Formation and Properties (Volume II))
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Open AccessReview
Green and Sustainable Rare Earth Element Recycling and Reuse from End-of-Life Permanent Magnets
by
Zara Cherkezova-Zheleva, Marian Burada, Anca Elena Sobetkii (Slobozeanu), Daniela Paneva, Sabina Andreea Fironda and Radu-Robert Piticescu
Metals 2024, 14(6), 658; https://doi.org/10.3390/met14060658 - 1 Jun 2024
Abstract
Rare earth elements (REEs) are key materials for the development of renewable energy devices such as high-power magnets for wind turbines, electric vehicles, or fuel cells for hydrogen generation, aiming to fulfill the objectives of the European Green Deal for a carbon-neutral economy.
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Rare earth elements (REEs) are key materials for the development of renewable energy devices such as high-power magnets for wind turbines, electric vehicles, or fuel cells for hydrogen generation, aiming to fulfill the objectives of the European Green Deal for a carbon-neutral economy. The increased demand for REEs and their criticality strongly require the improvement of their extraction technologies from primary resources and the enhancement of their circularity reuse rate from secondary resources. The aim of this paper is to focus attention on the possibilities offered by emerging methods such as microwave (MW) treatment and mechanochemistry in waste electric and electronic equipment (WEEE) processing and the reuse of end-of-life (EoL) magnets, directed toward the tailoring of rational REE material flows. The discussed investigation examples explore some key features of conventional and new methods for efficient, environmentally friendly, and scalable REE extraction and reuse, with the final goal of producing recycled NdFeB powders, with potential use in the redesign and fabrication of new REE-based magnets.
Full article
(This article belongs to the Special Issue Recovery of Critical Metals and Materials from Residues)
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Open AccessArticle
A Metal Accelerator Approach for Discharging Cylindrical Lithium-Ion Batteries in a Salt Solution
by
Erdenebold Urtnasan and Jei-Pil Wang
Metals 2024, 14(6), 657; https://doi.org/10.3390/met14060657 - 31 May 2024
Abstract
Recycling lithium-ion batteries provides sustainable raw materials. Crushing and separation are necessary for extracting metals, like lithium, from batteries. Crushing a battery carries a risk of fire or explosion. Fully discharging the battery is crucial for safe production. Discharging batteries in a salt
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Recycling lithium-ion batteries provides sustainable raw materials. Crushing and separation are necessary for extracting metals, like lithium, from batteries. Crushing a battery carries a risk of fire or explosion. Fully discharging the battery is crucial for safe production. Discharging batteries in a salt solution is a simple and cost-effective large-scale process. However, it is important to note that there is a potential risk of corrosion and loss of battery elements when batteries are immersed in a salt solution. The purpose of this study is to investigate the effectiveness of two distinct methodologies at enhancing the voltage drop of a cylindrical battery when immersed in a salt solution while preventing corrosion. These techniques involve the application of iron and copper accelerators. A 20 wt.% salt water solution was chosen based on the research of several researchers. As the current flows through the metal parts, it encounters electrical resistance and forms an electric circuit with the electrolyte solution. This interaction converts electrical energy into various physical–electrical–electrochemical phenomena, leading to a decrease in battery voltage. Research revealed that the battery can be discharged up to 100% within 4 h without causing corrosion to its components. Another point to note is that if copper conductors are used, it is possible to decrease the battery voltage by around 90% within 8 h. The gap between the copper conductor and the battery had a direct impact on the battery’s discharge rate. Reducing the distance significantly increased the discharge rate, as confirmed by experimental evidence. This discharge mechanism was thoroughly described in a schematic, and, to further explain the electrochemical reaction, the Pourbaix diagram was utilized for both the Fe-Na-Cl and Cu-Na-Cl systems. Moreover, our theoretical predictions were validated through a chemical and mineralogical analysis of the precipitates that formed in the solution.
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(This article belongs to the Special Issue Recovery and Utilization of Metallurgical Solid Wastes)
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Open AccessArticle
Local Buckling of Locally Sharp-Notched C2700 Brass Circular Tubes Subjected to Cyclic Bending
by
Yu-An Chen and Wen-Fung Pan
Metals 2024, 14(6), 656; https://doi.org/10.3390/met14060656 - 31 May 2024
Abstract
This paper aims to investigate the response and local buckling of locally sharp-notched C2700 brass circular tubes (LSN C2700 brass circular tubes) under cyclic bending loads. The study considers four different notch orientations (0°, 30°, 60°, and 90°) and five distinct notch depths
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This paper aims to investigate the response and local buckling of locally sharp-notched C2700 brass circular tubes (LSN C2700 brass circular tubes) under cyclic bending loads. The study considers four different notch orientations (0°, 30°, 60°, and 90°) and five distinct notch depths (0.2, 0.4, 0.6, 0.8, and 1.0 mm). The results reveal that notch orientation and depth exert minimal impact on the moment–curvature relationship, leading to the formation of stable loops. The ovalization–curvature graphs demonstrate a trend of symmetry, serration, and growth with an increasing number of bending cycles. Additionally, larger notch orientations or smaller notch depths result in reduced ovalization. Furthermore, the double logarithmic coordinates of controlled curvature–number of cycles necessary to induce local buckling reveal five non-parallel lines representing different notch depths when the notch orientation is fixed. Finally, by adopting the formulas for smooth tubes and for locally sharp-notched 304 stainless steel circular tubes (LSN SS304 circular tubes), this study adjusts the related material parameters accordingly. These modifications effectively describe the controlled curvature–number of cycles necessary to induce local buckling for LSN C2700 brass circular tubes with different notch orientations and depths under cyclic bending, demonstrating reasonable agreement with the experimental results.
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(This article belongs to the Special Issue Failure and Degradation of Metals)
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Open AccessArticle
Effect of Nd on Functional Properties of Biodegradable Zn Implants in In Vitro Environment
by
Efrat Hazan-Paikin, Lital Ben Tzion-Mottye, Maxim Bassis, Tomer Ron and Eli Aghion
Metals 2024, 14(6), 655; https://doi.org/10.3390/met14060655 - 31 May 2024
Abstract
The present study aims to evaluate the effect of up to 3 wt.% Nd on pure Zn in terms of physical properties and in vitro analysis. The use of Nd as an alloying element is due to its relatively adequate biocompatibility and its
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The present study aims to evaluate the effect of up to 3 wt.% Nd on pure Zn in terms of physical properties and in vitro analysis. The use of Nd as an alloying element is due to its relatively adequate biocompatibility and its potential capability to reinforce metals with a hexagonal close-packed (HCP) crystal structure, such as Mg and Zn. The microstructural assessment was executed using X-ray diffraction analysis, along with optical and scanning electron microscopy. The mechanical properties were evaluated by hardness and tensile strength testing. The corrosion performance in simulated physiological environments was examined by means of immersion tests, potentiodynamic polarization, and impedance spectroscopy using phosphate-buffered saline (PBS) solution. Cytotoxicity assessment was carried out by indirect cell viability analysis according to the ISO 10993-5/12 standard using Mus musculus 4T1 cells, which are known to be very sensitive to toxic environments. The obtained results clearly highlighted the reinforcing effect of Nd in Zn-base alloys, mainly due to the formation of a secondary phase: NdZn5. This strengthening effect was acquired without impairing the inherent ductility and corrosion performance of the tested alloys. The cytotoxicity assessment indicated that the addition of Nd has a strong favorable effect on cell viability, which stimulates the inherent anti-inflammatory characteristics of Zn.
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(This article belongs to the Section Biobased and Biodegradable Metals)
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Open AccessArticle
The Formation Mechanism of Oxide Inclusions in a High-Aluminum Ni-Based Superalloy during the Vacuum Induction Remelting Process
by
Lihui Zhang, Erkang Liu, Weijie Xing, Zhaojiang Xue, Wenjie Fan, Yunsong Zhao, Yushi Luo, Changchun Ge and Min Xia
Metals 2024, 14(6), 654; https://doi.org/10.3390/met14060654 - 30 May 2024
Abstract
Oxide inclusions in Ni-based superalloys play a crucial role in determining their mechanical properties, oxidation resistance, and corrosion resistance at high temperatures. In this paper, the source and formation mechanism of different types of oxide inclusions in a high-aluminum Ni-based superalloy were systematically
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Oxide inclusions in Ni-based superalloys play a crucial role in determining their mechanical properties, oxidation resistance, and corrosion resistance at high temperatures. In this paper, the source and formation mechanism of different types of oxide inclusions in a high-aluminum Ni-based superalloy were systematically studied. An automatic field emission scanning electron microscope equipped with an energy dispersive spectrometer and a self-designed superalloy inclusion analysis standard was utilized to quantitatively reveal the oxide inclusion characteristics of the high-aluminum Ni-based superalloy prepared via vacuum induction melting (VIM) and vacuum induction remelting (VIR) processes. The experimental results indicate that the typical oxide inclusions in the Ni-based superalloy before the VIR process are irregular MgO·Al2O3 inclusions with sizes of less than 2 μm. After the VIR process, the typical oxide inclusions in the Ni-based superalloy are also MgO·Al2O3 inclusions. However, these oxide inclusions can be classified into three categories: (i) endogenous irregular MgO·Al2O3 inclusions, less than 4.3 μm in size, inherited from the master alloy; (ii) several hundred-micron film-like MgO·Al2O3 inclusions generated as interface reaction products between the MgO crucible and melts; and (iii) millimeter-scale MgO·Al2O3 inclusions and several tens of microns of MgO inclusions from the exfoliation of the MgO crucible matrix.
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(This article belongs to the Special Issue Solidification and Casting of Metals and Alloys)
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Comparative Analysis of Three Different Probe Designs for Reducing Hook Defects in FSW of AA6005-T6 Aluminum Alloy
by
Liuyang Qin, Hongxia Zhang, Gongbo Bian, Kewei Li and Peng Dong
Metals 2024, 14(6), 653; https://doi.org/10.3390/met14060653 - 30 May 2024
Abstract
Hook defects are common in FSW butt–lap joints, resulting in a significant safety hazard for the parts that suffer cyclic load. In this study, a numerical simulation based on the Euler–Lagrange coupling method was conducted to investigate the formation process of hook defect
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Hook defects are common in FSW butt–lap joints, resulting in a significant safety hazard for the parts that suffer cyclic load. In this study, a numerical simulation based on the Euler–Lagrange coupling method was conducted to investigate the formation process of hook defect during FSW of AA6005-T6 aluminum alloy. The simulation results were validated with experimental data, showing good agreement. The formation of the hook defect is caused by the threads on the probe promoting material flow in the thickness direction. In order to further study the effect of probe morphology on hook defects, three kinds of probe models with different morphology were established and numerically simulated by the CEL method. The simulation results show that all three kinds of probes can reduce the size of the hook. The welds obtained using the left–left probe (LLP) and the three-plane probe (TPP) both exhibit void defects, while the welds obtained by a right–left probe (RLP) have no internal void defects. The experimental results show the same characteristics as the simulation results, and the size of the hook defect is reduced to 58 μm.
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(This article belongs to the Special Issue Recent Trends in Friction Stir-Related Manufacturing Technologies)
Open AccessArticle
A Study on the Influence of Different Defect Types on the Corrosion Behavior of Q235/TA2 Composite Plates in a Marine Environment
by
Jianbo Jiang, Nannan Li, Bingqin Wang, Fangfang Liu, Chao Liu and Xuequn Cheng
Metals 2024, 14(6), 652; https://doi.org/10.3390/met14060652 - 30 May 2024
Abstract
The structural design of steel–titanium composite plates significantly affects their corrosion resistance. To investigate the impact of defects of different shapes and sizes on the corrosion behavior of steel–titanium composite plates, this study designed six types of defects and conducted a series of
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The structural design of steel–titanium composite plates significantly affects their corrosion resistance. To investigate the impact of defects of different shapes and sizes on the corrosion behavior of steel–titanium composite plates, this study designed six types of defects and conducted a series of characterization tests. The results showed that due to the galvanic interaction between carbon steel and titanium alloy, small defects initially accelerate corrosion, resulting in 50% to 200% more corrosion weight loss compared to large defects. However, in the later stages of immersion, the corrosion rate of small defects decreased by up to 35%, which was attributed to the accumulation of protective corrosion products. Additionally, there is an inverse relationship between the corrosion rate and the thickness ratio of the composite plate. The reduction in the area of Q345B also results in additional corrosion loss of up to 32%.
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(This article belongs to the Special Issue Advances in Corrosion and Protection of Materials (Second Edition))
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