Metals

20 pages, 16490 KiB

Open AccessArticle

Flow-Field Characterization of Kanbara Reactor Based on Numerical Simulations

by Jingjing Han, Yanling Zhang, Zheng Zhao and Geng Li

Metals 2025, 15(2), 223; https://doi.org/10.3390/met15020223 - 19 Feb 2025

Viewed by 429

The KR desulfurization process in steel plants faces challenges, such as excessive temperature drop and low lime utilization. This study employs numerical simulations to analyze the effects of cross-shaped impeller dimensions on the flow field, velocity distribution, temperature drop, and slag–metal mixing behavior [...] Read more.

The KR desulfurization process in steel plants faces challenges, such as excessive temperature drop and low lime utilization. This study employs numerical simulations to analyze the effects of cross-shaped impeller dimensions on the flow field, velocity distribution, temperature drop, and slag–metal mixing behavior within the molten metal. Optimization parameters were identified to minimize the temperature drop while maintaining the mixing efficiency. Furthermore, a novel perforated cross-shaped impeller design was proposed to enhance slag–metal mixing. The simulation results demonstrate that compared to the conventional cross-shaped impeller, the optimized design increases the molten metal capacity by 2 tons and reduces the temperature drop by 16 °C under identical initial liquid level conditions. Full article

(This article belongs to the Special Issue Green Super-Clean Steels)

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16 pages, 4063 KiB

Open AccessArticle

Kinetics of Oxidation of Binary Ti-Cu Alloys in the 600–800 °C Temperature Range

by Fatemah Alqattan, Fei Yang and Leandro Bolzoni

Metals 2025, 15(2), 222; https://doi.org/10.3390/met15020222 - 18 Feb 2025

Viewed by 444

Abstract

The oxidation behaviour of Ti alloys is a crucial aspect for structural components operating at high service temperature. The aim of this study is to identify the oxidation kinetics and mechanism of binary Ti-Cu alloys with a progressively higher amount of Cu with [...] Read more.

The oxidation behaviour of Ti alloys is a crucial aspect for structural components operating at high service temperature. The aim of this study is to identify the oxidation kinetics and mechanism of binary Ti-Cu alloys with a progressively higher amount of Cu with the alloys having a α + β lamellar structure. It is found that all the alloys followed a non-ideal (i.e., n ≠ 2) parabolic relationship, as controlled by anionic oxygen diffusion, with a distinct effect from both oxidation temperature and alloy chemistry. Specifically, faster oxidation kinetics are found both at higher temperatures and for higher Cu contents, resulting in the formation of thicker oxide scale layers. The oxidation mechanism primarily entails the formation of the stable TiO₂ rutile polymorph. However, transitions through metastable phases (e.g., anatase) and texturing of rutile are also revealed as dictated by the composition of the alloy at specific oxidation temperature/time pairs. Full article

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

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39 pages, 10913 KiB

Open AccessArticle

Corrosion Behavior of X65 API 5L Carbon Steel Under Simulated Storage Conditions: Influence of Gas Mixtures, Redox States, and Temperature Assessed Using Electrochemical Methods for up to 100 Hours

by Yendoube Charles Sano Moyeme, Stephanie Betelu, Johan Bertrand, Karine Groenen Serrano and Ioannis Ignatiadis

Metals 2025, 15(2), 221; https://doi.org/10.3390/met15020221 - 18 Feb 2025

Viewed by 520

Abstract

In the context of the deep geological disposal of high-level and intermediate-level long-lived radioactive waste in France, the Callovian–Oxfordian (Cox) clay formation has been selected as a natural barrier. Thus, understanding the corrosion phenomena between the carbon steel used (API 5L X65) for [...] Read more.

In the context of the deep geological disposal of high-level and intermediate-level long-lived radioactive waste in France, the Callovian–Oxfordian (Cox) clay formation has been selected as a natural barrier. Thus, understanding the corrosion phenomena between the carbon steel used (API 5L X65) for the waste lining tubes and the Cox pore water, as well as its possible future evolutions, is of great importance. A controlled laboratory experiment was conducted using robust handmade API 5L X65 carbon steel electrodes in synthetic Cox pore water under equilibrium with three distinct gas atmospheres, simulating oxic, anoxic, and sulfide-rich environments at 25 °C and 80 °C, in a batch-type electrochemical cell. The experimental methodology involved linear polarization resistance (LPR) cycles, electrochemical impedance spectroscopy (EIS), and Tafel extrapolation at regular intervals over a period of 70 to 100 h to elucidate corrosion mechanisms and obtain corrosion current densities. At the same time, the fluid’s key geochemical parameters (temperature, pH, and redox potential) were monitored for temporal variation. This study, with results showing high corrosion rates under the three conditions investigated at two temperatures, underscores the importance of controlling the immediate environment of the containment materials to prevent exposure to variable conditions and to ensure that corrosion remains controlled over the long term. Full article

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

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24 pages, 64785 KiB

Open AccessArticle

Compression Behaviour of L-PBF-Manufactured Ti6Al4V BCC Lattices

by John Daniel Arputharaj, Shahrooz Nafisi and Reza Ghomashchi

Metals 2025, 15(2), 220; https://doi.org/10.3390/met15020220 - 18 Feb 2025

Viewed by 467

Abstract

Laser powder bed fusion (L-PBF) is a widely used additive manufacturing technique that enables the creation of complex lattice structures with applications in biomedical implants and aerospace components. This study investigates the impact of relative density and the geometric parameters (unit cell size [...] Read more.

Laser powder bed fusion (L-PBF) is a widely used additive manufacturing technique that enables the creation of complex lattice structures with applications in biomedical implants and aerospace components. This study investigates the impact of relative density and the geometric parameters (unit cell size and strut diameter) of body-centred cubic (BCC) lattices on the compressive mechanical properties of Ti-6Al-4V (Ti64) lattices manufactured using continuous wave L-PBF. The as-built and heat-treated samples were evaluated for their Young’s modulus, strength, and ductility. Lattices with varying unit cell sizes (1–3 mm) and strut diameters (0.3–1.2 mm) were fabricated, resulting in relative densities ranging from 10% to 77%. All of these samples exhibited a 45° shear failure, which was attributed to the alignment of the principal stress planes with the lattice struts under compression, leading to shear band formation. This study provides critical insights into the interplay between geometric parameters, microstructure evolution, and resultant mechanical properties, contributing to the experimental validation of solid vs. lattice samples fabricated under identical conditions. Fractography analysis revealed that the as-built samples exhibited predominantly brittle fracture characteristics, while heat-treated samples displayed mixed fracture modes with increased ductility. Results indicate that heat treatment enhances mechanical properties, yielding comparable compressive strength (approx. 20% decrease), a reduced modulus of elasticity (approx. 30% decrease), and increased ductility (approx. 10% increase). This is driven by microstructural changes, such as the phase transformation from α’ martensitic needles to α + β, and thus relieves the residual stress to some degree. By addressing the microstructure–property correlations and failure mechanisms, this work establishes guidelines for optimizing lattice designs for biomedical and aerospace applications, emphasizing the critical role of geometric parameters and thermal treatment in tailoring mechanical behaviour. Full article

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

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22 pages, 7269 KiB

Open AccessArticle

An Inverse Piecewise Flow Curve Determination Method for Torsion Tests at Elevated Temperature

by Aditya Vuppala, Holger Brüggemann, David Bailly and Emad Scharifi

Metals 2025, 15(2), 219; https://doi.org/10.3390/met15020219 - 18 Feb 2025

Viewed by 369

Abstract

This paper presents an extended method for determining flow curves under shear loading using torsion tests, a technique often used to characterize plastic behavior in metal forming. Torsion tests are advantageous due to their ability to achieve flow curves up to large strains [...] Read more.

This paper presents an extended method for determining flow curves under shear loading using torsion tests, a technique often used to characterize plastic behavior in metal forming. Torsion tests are advantageous due to their ability to achieve flow curves up to large strains (~3) while maintaining stable specimen geometry during deformation. However, the strain and strain rate distribution across the specimen are non-uniform, increasing radially from the rotation axis. Traditional analytical methods, such as the Fields and Backofen approach, address this non-uniformity by considering average strain and strain rates. Conversely, inverse approaches, which rely on fitting constitutive equations through iterative procedures, are more sensitive to the choice of empirical equations and can be computationally expensive. To address these issues, this study adapts an inverse piecewise flow curve determination method from compression tests for use in torsion tests. A stepwise methodology is proposed to calculate constant strain rates and isothermal flow curves, where flow curves for the lowest strain rates are first determined and subsequently used to derive flow curves at higher strain rates. The proposed approach was applied to the case-hardened steel 16MnCrS5, with tests conducted at temperatures ranging from 900 °C to 1100 °C and strain rates from 0.01 s⁻¹ to 1 s⁻¹. The experimental data obtained were successfully replicated by the flow curves with a maximum deviation of only 1%. The results demonstrate the efficiency and accuracy of the stepwise inverse approach for determining flow curves in torsion tests, making it appropriate for characterizing material behavior for metal-forming applications. Full article

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17 pages, 12589 KiB

Open AccessArticle

Analysis of the Influence of Process Parameters on Transverse Flux Induction Heating of Endless-Rolling Strip

by Lin Gao, Fang-Zhou Shi, Meng Yan, Yi-Ping He, Jian Xiang, Xiao-Hu Qi and Hua-Gui Huang

Metals 2025, 15(2), 218; https://doi.org/10.3390/met15020218 - 18 Feb 2025

Viewed by 459

Abstract

This study focuses on the effect of an induction heating device on the entry of a thin strip continuous casting and rolling line. A finite element model for the electromagnetic–thermal coupling of transverse magnetic flux induction heating was developed by adopting COMSOL software [...] Read more.

This study focuses on the effect of an induction heating device on the entry of a thin strip continuous casting and rolling line. A finite element model for the electromagnetic–thermal coupling of transverse magnetic flux induction heating was developed by adopting COMSOL software 6.1 to systematically investigate the effects of process parameters on the magnetic field, eddy current field, and the transverse temperature distribution of the strip. The results show that when the gap is between 20 mm and 40 mm, the maximum value of magnetic induction in the overheating region at the edges of the strip increases from 0.28 T to 0.35 T and 0.38. When the strip width is 1000 mm, there is an approximately 29% increase in magnetic induction in comparison to a strip with a width of 800 mm, and both eddy current density and temperature exhibit abnormal fluctuations. The maximum temperature difference in the temperature uniformity region at the center of the strip is only 3 °C at different frequencies, and the temperature-rise curves almost completely overlap. With increasing current, the temperature difference between the weak temperature region and the temperature uniformity region at the center widens, indicating a deterioration in temperature uniformity. Meanwhile, the field conditions are simulated using a simplified model of continuous heating. The results indicate that the maximum temperature deviation in the overheating region at the edges of the strip is 6 °C, while the deviation in the temperature uniformity region is 2 °C. Furthermore, the simulation data reveal an average temperature rise of 1156 °C across the width of the strip, with a deviation of 1.4 °C compared to the measured results, which verifies the validity of the proposed model. The analysis results provide a reference basis for designing transverse magnetic flux induction heating devices and optimizing process parameters. Full article

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13 pages, 7676 KiB

Open AccessArticle

Effect of Normalizing Temperature on Microstructure, Texture and Magnetic Properties of Non-Oriented Silicon Steel

by Changcheng Zhou, Shenteng Luan, Jialong Qiao and Haijun Wang

Metals 2025, 15(2), 217; https://doi.org/10.3390/met15020217 - 18 Feb 2025

Viewed by 2148

Abstract

In order to improve the magnetic properties of non-oriented silicon steel, the effects of different normalizing temperatures on the microstructure, texture, and magnetic properties of 3.0%Si 0.8%Al non-oriented silicon steel were studied by OM, EBSD, and a magnetic measuring instrument. The results show [...] Read more.

In order to improve the magnetic properties of non-oriented silicon steel, the effects of different normalizing temperatures on the microstructure, texture, and magnetic properties of 3.0%Si 0.8%Al non-oriented silicon steel were studied by OM, EBSD, and a magnetic measuring instrument. The results show that the microstructure of the hot-rolled plate is obviously different along the thickness direction. Strong Goss texture and {001} ~ {112} texture are the main textures in the hot-rolled plate. After normalizing at 900 °C, 940 °C, and 980 °C and annealing at 940 °C, respectively, the average grain size of the normalized plates and the annealed sheets increases with the increase in the normalizing temperature, and the texture types of the normalized plates basically inherit that of the hot-rolled plates. With the increase in normalizing temperature, the intensity of the γ-fiber texture decreases, and the main texture types in the finished plates are {100} <012> texture and {111} <112> texture. The area fraction of {100} <012> texture in the finished sheet normalized at 980 °C and annealed is the largest, which is 20.3%, and the area fraction of {114} <481> texture is larger, which is 15.2%. The magnetic induction B₅₀ of the finished sheets increases gradually with the increase in the normalizing temperature, from 1.662 T to 1.720 T; the low-frequency iron loss P_1.5/50 decreased slightly from 2.46 W·kg⁻¹ to 2.30 W·kg⁻¹. The high-frequency iron loss P_1.0/400 decreased significantly from 17.40 W·kg⁻¹ to 15.75 W·kg⁻¹. The results of the microstructure, texture, and magnetic properties show that the best normalizing temperature in this experiment is 980 °C. Full article

(This article belongs to the Special Issue Green Super-Clean Steels)

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11 pages, 8951 KiB

Open AccessArticle

Various Manufacturing Technologies and Their Influence on the Fatigue Strength of Cu-Mg Wires

by Paweł Strzępek, Andrzej Nowak and Małgorzata Zasadzińska

Metals 2025, 15(2), 216; https://doi.org/10.3390/met15020216 - 18 Feb 2025

Viewed by 419

Abstract

Copper alloys are widely used in many branches of industry due to their excellent corrosion resistance and high level of both electrical conductivity and strength. Among others, there are copper alloys with magnesium, which are known and commonly used with Mg content of [...] Read more.

Copper alloys are widely used in many branches of industry due to their excellent corrosion resistance and high level of both electrical conductivity and strength. Among others, there are copper alloys with magnesium, which are known and commonly used with Mg content of up to 0.7 wt.%. Here, we study Cu-Mg alloys with 2.8 wt.% and 3.2 wt.% of Mg, the properties of which are yet to be determined. One of these is the fatigue strength of materials, which is crucial for maintaining the long-term and safe operation of wires in engineering applications. Fatigue is a process during which materials are subjected to cyclic stress below the ultimate tensile strength of materials, leading to their damage or failure. In the current paper, CuMg2.8 and CuMg3.2 wires were obtained using a laboratory chain drawbench and an industrial drum-type drawing machine to verify the influence of manufacturing technology on the fatigue strength of materials. The obtained results were correlated with analogically obtained copper wires by taking into consideration the influence of the chemical composition, structure of fractures, stress and manufacturing technology. It was discovered that it is possible to obtain wires regardless of the drawing machine type and the concentration of Mg. However, CuMg3.2 wires obtained in the industrial conditions experienced delamination and brittle fractures during unwinding from the drum, and thus, their use was not possible. Full article

(This article belongs to the Special Issue Advances in Metal Materials: Structure, Properties and Heat Treatment)

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31 pages, 3890 KiB

Open AccessReview

A Review on the Magnetovolume Effect of the Full Heusler Alloys Ni₂MnZ (Z = In, Sn, Sb)

by Takeshi Kanomata, Xiao Xu, Takuo Sakon, Yuki Nagata, Shin Imada, Toshihiro Omori, Ryosuke Kainuma, Tetsujiro Eto, Yoshiya Adachi, Takumi Kihara, Yasushi Amako, Masaaki Doi and Yoshiya Uwatoko

Metals 2025, 15(2), 215; https://doi.org/10.3390/met15020215 - 18 Feb 2025

Viewed by 623

Abstract

The full Heusler alloys Ni₂MnZ (Z = In, Sn, Sb) exhibit ferromagnetic properties with a Curie temperature (T_C) above room temperature. The magnetic properties of Ni₂MnZ (Z = In, Sn, Sb) were studied through a combination [...] Read more.

The full Heusler alloys Ni₂MnZ (Z = In, Sn, Sb) exhibit ferromagnetic properties with a Curie temperature (T_C) above room temperature. The magnetic properties of Ni₂MnZ (Z = In, Sn, Sb) were studied through a combination of experiments and band calculations under ambient and elevated pressures. The main results of this study open up further prospects for controlling the magnetic properties of the multifunctional Heusler alloys Ni₂Mn_1+xZ_1−x (Z = In, Sn, Sb) and their practical application. Full article

(This article belongs to the Section Metallic Functional Materials)

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23 pages, 3660 KiB

Open AccessArticle

The Treatment of Iron-Containing Foundry Dusts with the Aim of Their Recycling and Their Effect on the Properties of Cast Iron

by Patrik Fedorko, Alena Pribulova, Peter Futas, Marcela Pokusova, Jozef Petrik, Peter Blasko, Marcin Brzeziński and Mariusz Łucarz

Metals 2025, 15(2), 214; https://doi.org/10.3390/met15020214 - 18 Feb 2025

Viewed by 540

Abstract

The foundry industry is an industry with a large production of waste. One such type of waste is fine-grained to dust-like waste, depending on the stage of the foundry process in which it is generated. As part of this research, dust samples were [...] Read more.

The foundry industry is an industry with a large production of waste. One such type of waste is fine-grained to dust-like waste, depending on the stage of the foundry process in which it is generated. As part of this research, dust samples were collected from three Slovak foundries producing castings from gray iron, ductile iron, and steel. The aim of the experiments was to recycle iron from dust materials in the foundry process. Based on the chemical composition of the dust, samples with the highest iron content were selected and added to the charge of the electric induction furnace (EIF). Since it was not possible to add dust material directly into the EIF, the dust was modified by pelletizing and briquetting using three types of binders selected according to the foundries’ requirements. Pellets were prepared using dust from only one type of foundry waste and were used as part of the charge in the EIF. In the case of briquetting, different binder contents in the briquette mixture were tested to evaluate their effect on the strength and disintegration of the briquettes. Based on the foundries’ requirements that the binder had to be low-cost and that we had to not contaminate the melt (thus requiring a minimal amount), not affect the furnace operation, and not degrade the properties of the produced cast iron, briquettes with the best properties were selected and used as part of the charge for cast iron production. Samples of the cast iron produced this way were taken for chemical analysis, and specimens were prepared for tensile strength testing. The results showed that the use of briquettes, in limited amounts, did not have a negative impact on the chemical composition of the cast iron, the melting process, or its tensile strength. Full article

(This article belongs to the Special Issue Comprehensive Recycling of Metallurgical Solid Waste and Mineral Resources)

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13 pages, 5304 KiB

Open AccessArticle

Effect of Ag and Ti Addition on the Deformation and Tribological Behavior of Zr-Co-Al Bulk Metallic Glass

by Siva Shankar Alla, Mohammad Eskandari, Shristy Jha, Ziyu Pei, S. Vincent, Wook Ha Ryu, Eun Soo Park and Sundeep Mukherjee

Metals 2025, 15(2), 213; https://doi.org/10.3390/met15020213 - 18 Feb 2025

Viewed by 488

Abstract

The effects of a small addition of Ag and Ti on the thermal stability, mechanical properties, and tribological behavior of Zr-Co-Al bulk metallic glass (BMG) were investigated. A 5 at.% addition of Ag and Ti to the Zr-Co-Al base alloy improved the thermal [...] Read more.

The effects of a small addition of Ag and Ti on the thermal stability, mechanical properties, and tribological behavior of Zr-Co-Al bulk metallic glass (BMG) were investigated. A 5 at.% addition of Ag and Ti to the Zr-Co-Al base alloy improved the thermal stability and had no significant effect on the mechanical properties but considerably improved the wear behavior. The coefficient of friction decreased while the wear rate increased with increasing normal loads for all three alloys. Zr-Co-Al-Ti showed the best tribological performance among the studied alloys, with coefficient of friction and wear rate lower by a factor of four compared to Zr-Co-Al BMG. Predominantly oxidative wear was seen for the quaternary Zr-Co-Al-Ag and Zr-Co-Al-Ti BMGs at higher loads in contrast to abrasive and adhesive wear for the ternary Zr-Co-Al base alloy. These results highlight the potential of Ag and Ti micro-alloying for improving the mechanical and tribological properties of Zr-based amorphous alloys. Full article

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11 pages, 2351 KiB

Open AccessArticle

Extraction of Rhenium with Trialkylbenzylammonium Chloride

by I. A. Kalina, E. V. Zlobina, Zh. Zh. Bekishev, A. G. Ismailova, Kh. S. Tassibekov, Z. A. Iskakov, B. Zh. Toksanbayev, A. T. Kumarbekova and A. S. Fomenko

Metals 2025, 15(2), 212; https://doi.org/10.3390/met15020212 - 18 Feb 2025

Viewed by 431

Abstract

This study investigates the extraction of rhenium using trialkylbenzyl ammonium chloride (TABAC) as an alternative to trialkylamine (TAA) for recovering rhenium from highly diluted solutions. Rhenium, present as ReO₄⁻ over a wide acidity range, was extracted via an anion exchange mechanism [...] Read more.

This study investigates the extraction of rhenium using trialkylbenzyl ammonium chloride (TABAC) as an alternative to trialkylamine (TAA) for recovering rhenium from highly diluted solutions. Rhenium, present as ReO₄⁻ over a wide acidity range, was extracted via an anion exchange mechanism in single-stage experiments monitored by inductively coupled plasma mass spectrometry (ICP-MS). Key variables, including pH, acid concentration, and the concentrations of extractant and metal, were examined. The results demonstrated a high extraction efficiency exceeding 99% within a pH range of 2 to 7 and from solutions containing sulfuric or hydrochloric acid at concentrations of 0.1 to 3.0 M (mol/L). However, extraction from nitric acid solutions was less efficient, with less than 30% recovery. Performance for both TAA-kerosene and TABAC-kerosene followed the order H₂SO₄ > HCl > HNO₃. The optimal TABAC concentration was 10⁻² M (mol/L) in kerosene. TABAC also showed higher selectivity than TAA, with separation coefficients Re/Mo = 66.8 and Re/W = 55.8 in 0.1–1.0 M (mol/L) sulfuric acid. Based on equilibrium studies, the complexes formed during extraction were identified as [R₃R′NH]ReO₄. This approach may offer environmentally friendly and cost-effective benefits for large-scale industrial applications, enabling efficient recovery of valuable rhenium while reducing waste and environmental impact. Full article

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14 pages, 3809 KiB

Open AccessArticle

Diffusion Behavior and Kinetics of the Iron–Nickel Interface During Annealing Treatment

by Wenlin Wu, Fei Zhong, Pu Zhou, Jue Lu and Feng Wang

Metals 2025, 15(2), 211; https://doi.org/10.3390/met15020211 - 17 Feb 2025

Viewed by 533

Abstract

The notorious corrosion resistance of carbon steel significantly limits its scope of application. In this study, a strategy involving electrodeposited nickel followed by annealing was proposed to improve the corrosion resistance of materials. The effects of annealing on the microstructure of nickel-plated steel [...] Read more.

The notorious corrosion resistance of carbon steel significantly limits its scope of application. In this study, a strategy involving electrodeposited nickel followed by annealing was proposed to improve the corrosion resistance of materials. The effects of annealing on the microstructure of nickel-plated steel were investigated by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The results reveal annealing induces Fe-Ni alloy layer formation at the plating–substrate interface, with thicknesses ranging from 2.2 μm to 4.8 μm as the temperature increases from 650 °C to 800 °C and the duration extends from 1 min to 5 min. Additionally, a diffusion kinetics model based on Fick’s second law was established to describe the diffusion process of nickel atoms in the iron matrix. The diffusion coefficients of nickel atoms were determined to be in the range of 4.4 × 10−16 m²·s⁻¹ to 1.26 × 10−15 m²·s⁻¹ under the tested conditions. This model provides a theoretical framework for optimizing annealing treatments to enhance the performance of nickel-coated carbon steel components. Full article

(This article belongs to the Special Issue Surface Engineering and Heat Treatment of Metals and Alloys)

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16 pages, 4789 KiB

Open AccessArticle

Effect of Porosity on the Corrosion Behavior of FeCoNiMnCr_x Porous High-Entropy Alloy in 3.5 Wt.% NaCl Solution

by Ying Wang, Shuobin Chen, Yuhua Peng, Xijie Zheng, Dong Li, Cheng Nie, Pan Gong, Zhigang Hu and Ming Ma

Metals 2025, 15(2), 210; https://doi.org/10.3390/met15020210 - 17 Feb 2025

Viewed by 395

Abstract

The effects of different Cr contents on the corrosion resistance of FeCoNiMnCr_x (x = 0.5;1;1.5) porous high-entropy alloys (HEAs) in 3.5 wt.% NaCl solution on corrosion resistance was investigated. With the increase in Cr content, the total porosity and permeability of [...] Read more.

The effects of different Cr contents on the corrosion resistance of FeCoNiMnCr_x (x = 0.5;1;1.5) porous high-entropy alloys (HEAs) in 3.5 wt.% NaCl solution on corrosion resistance was investigated. With the increase in Cr content, the total porosity and permeability of the porous HEA increased. The increase in porosity improves the interconnectivity between the pores and enhances the contact area with the corrosion solution. The pore-making mechanism is mainly a powder compaction, and Kirkendall holes are caused by different elements due to different diffusion rates. With the increase in Cr content, the i_corr increases, and the E_corr decreases in the porous HEAs of FeCoNiMnCr_x (x = 0.5;1;1.5). The corrosion resistance of FeCoNiMnCr_x (x = 0.5;1;1.5) porous HEAs decreases with the increase in the Cr element. With the increase in Cr content, the weight gain rate of FeCoNiMnCr_x porous HEA increases gradually after immersion for 168 h, and the average pore size and permeability of the sample decrease gradually. The corrosion resistance of FeCoNiMnCr_x porous HEA decreases with increasing Cr content. Full article

(This article belongs to the Special Issue High-Temperature Corrosion and Oxidation of Metallic Materials)

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19 pages, 12490 KiB

Open AccessArticle

Feasibility Exploration and Research Examples of On-Site Metallographic Inspection Methods in the Analysis of Bronze Artifacts—A Case Study of Ming Jiajing Bronze Lions and the Shang Bronze Tripod Vessel with Cicada Designs

by Kaige Zhang, Cheng Liu, Siyu Zhang, Ruihua Cui and Yi Li

Metals 2025, 15(2), 209; https://doi.org/10.3390/met15020209 - 17 Feb 2025

Viewed by 459

Abstract

This study explores a new microdestructive on-site metallographic inspection technique for analyzing metal artifacts. In the current archeometrical work, the metallographic analysis of metal artifacts requires mechanical sampling, which not only damages the integrity of the artifacts but also brings cold working effects [...] Read more.

This study explores a new microdestructive on-site metallographic inspection technique for analyzing metal artifacts. In the current archeometrical work, the metallographic analysis of metal artifacts requires mechanical sampling, which not only damages the integrity of the artifacts but also brings cold working effects to the metallographic structure during the sampling process, making the information inaccurate. This study designed a set of detailed on-site metallographic inspection methods for bronze artifacts, including grinding, sealing, polishing, etching, replicating, cleaning, and other steps. After verifying its safety through simulation experiments, the method was applied to several precious bronze artifacts, including two Ming Dynasty bronze lions from the Xi’an Beilin Museum and a Shang Bronze Tripod Vessel with Cicada Designs from the China Bronze Ware Museum. The metallographic findings show that the in situ metallographic technique can flexibly and accurately reveal the metallographic texture and process information of each localized part of the bronze artifacts, e.g., the heat-affected zone of the coins on the surface of the Ming Dynasty bronze lions proved the casting-inlay process, and the different heat texture of each foot of the Shang Bronze Tripod Vessel with Cicada Designs proved the chronological sequence of its two historical restorations. This study provides a novel approach to the process analysis of bronze artifacts, a method that can provide significant advantages in analyzing the processing techniques of precious and intact artifacts. Full article

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21 pages, 6624 KiB

Open AccessArticle

High-Efficiency Extraction of Lithium and Aluminum from Coal Fly Ash Using Activation-Sintering Technology

by Chenliang Zhang, Yanheng Li, Qiaojing Zhao, Mingjing Xu, Bin Yao, Pengpeng Zhang, Xuan Ji and Jiawei Fan

Metals 2025, 15(2), 208; https://doi.org/10.3390/met15020208 - 17 Feb 2025

Viewed by 344

Abstract

The objective of this study was to investigate the potential for extracting lithium and aluminum from coal fly ash in depth. The activation-sintering method was used to study how factors like activators, sintering agents, sintering time, leaching concentration, and temperature affect the leaching [...] Read more.

The objective of this study was to investigate the potential for extracting lithium and aluminum from coal fly ash in depth. The activation-sintering method was used to study how factors like activators, sintering agents, sintering time, leaching concentration, and temperature affect the leaching of lithium and aluminum. A 1:2 Na₂CO₃ activator was proportioned with coal fly ash for primary incineration at a temperature of 1000 °C for 30 min, after which a 3:1 Na₂SO₄ sintering agent was added to be proportioned with coal fly ash for secondary incineration at a temperature of 1000 °C for 30 min. The temperature was then increased to 400 °C for 60 min, after which the lithium and aluminum were leached with a 1% H₂SO₄ solution at 80 °C for 60 min. The leaching process was highly effective, with the lithium and aluminum leached out at rates of approximately 80%. Full article

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14 pages, 3644 KiB

Open AccessArticle

Microstructure and Performance of Body-Centered Cubic-Based Dual-Phase Composite Eutectic High-Entropy Alloys Prepared by Si Doping

by Saike Liu, Aoxiang Li, Kaiwen Kang, Jinshan Zhang, Di Huang, Chunning Che, Yiteng Jiang, Mingkun Xu, Borui Zhang, Yaqing Li and Gong Li

Metals 2025, 15(2), 207; https://doi.org/10.3390/met15020207 - 16 Feb 2025

Viewed by 586

Abstract

AlCrFeNi-based high-entropy alloys (HEAs) have emerged as a prominent research system, attracting significant interest due to their compositional diversity and the tunability of their phase structures. However, in practical applications, single-phase AlCrFeNi-based HEAs often face a trade-off between toughness and strength. Therefore, designing [...] Read more.

AlCrFeNi-based high-entropy alloys (HEAs) have emerged as a prominent research system, attracting significant interest due to their compositional diversity and the tunability of their phase structures. However, in practical applications, single-phase AlCrFeNi-based HEAs often face a trade-off between toughness and strength. Therefore, designing multi-phase composite eutectic high-entropy alloys (EHEAs) to optimize their mechanical properties and microstructure has become a key research focus. Si, a common non-metallic element, plays a significant role in strengthening metal materials. In this paper, AlCrFeNi with Si doping strengthening (AlCrFeNi)100-xSix composite EHEAs were successfully fabricated. A systematic analysis was conducted to investigate the impacts of Si doping on the microstructure and mechanical properties of AlCrFeNi-based composite EHEAs. This study shows that with increasing Si content, the biphasic lamellar composite structure at the grain boundaries gradually expands, forming flower petals. The precipitate structure within the grains evolves into flower disks, which form a sunflower-like composite structure in the alloy. The volume fraction of lamellar structures increases in the petals, accompanied by grain refinement. Furthermore, the yield strength of the alloy increases from 1131 MPa to 1360 MPa with increasing Si content. This provides guidance for the design of high-performance composite EHEAs. Full article

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

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15 pages, 8279 KiB

Open AccessArticle

Study on Liquid Metal Embrittlement Susceptibility of T91 Exposed to Liquid Lead-Bismuth Eutectic

by Jie Zhang, Bo Qin and Bin Long

Metals 2025, 15(2), 206; https://doi.org/10.3390/met15020206 - 15 Feb 2025

Viewed by 351

Abstract

In this study, slow strain rate tensile tests (SSRT) were performed on T91 in lead-bismuth eutectic (LBE) with saturated oxygen to investigate the effects of temperature (350 °C, 450 °C, and 550 °C), strain rate (1 × 10⁻⁵/s and 2 × [...] Read more.

In this study, slow strain rate tensile tests (SSRT) were performed on T91 in lead-bismuth eutectic (LBE) with saturated oxygen to investigate the effects of temperature (350 °C, 450 °C, and 550 °C), strain rate (1 × 10⁻⁵/s and 2 × 10⁻⁶/s) and pre-exposure conditions (time, oxygen concentration) on the sensitivity to liquid metal embrittlement (LME). The results revealed that the embrittlement sensitivity of T91 in LBE is significantly influenced by temperature. LME was observed in T91 at 350 °C and disappeared when the temperature increased to 550 °C. Additionally, T91 exhibited increased sensitivity to LME at low strain rates, indicating that low strain rates promoted the occurrence of LME. Finally, through different pre-exposure conditions, it was found that the obvious LME phenomenon would only occur when the oxygen concentration was poor and the pre-exposure time was long (48 h), indicating that pre-exposure conditions have a crucial impact on the occurrence of LME. Full article

(This article belongs to the Section Corrosion and Protection)

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11 pages, 1575 KiB

Open AccessArticle

Material and Process Modification to Improve Manufacturability of Low-Lead Copper Alloys by Low-Pressure Die Casting Method

by Ali Serdar Vanli and Muhammed Hakan Karas

Metals 2025, 15(2), 205; https://doi.org/10.3390/met15020205 - 15 Feb 2025

Viewed by 436

Abstract

Copper alloys are widely used in faucet production due to their formability, enabling the casting of complex shapes, as well as to their antibacterial properties and good corrosion resistance. This study examined a faucet produced by the low-pressure die casting method, focusing on [...] Read more.

Copper alloys are widely used in faucet production due to their formability, enabling the casting of complex shapes, as well as to their antibacterial properties and good corrosion resistance. This study examined a faucet produced by the low-pressure die casting method, focusing on alternatives to lead (Pb) in copper alloys. Fluidity, casting rejection rates, and mechanical and microstructural properties were assessed. Additionally, lead-free and environmentally friendly brass alloy developments in the literature were reviewed. The experimental work involved producing a faucet from aluminum, antimony, and a bismuth-modified low-lead alloy using low-pressure casting. As faucet material, the antimony-supplemented alloy exhibited superior strength and optimal hardness. It also demonstrated better microstructural distribution and the highest production efficiency (at 81%). These findings highlight the significant advantages of the addition of antimony over aluminum and bismuth in faucet casting. The results are promising for both the casting process and subsequent mechanical operations, suggesting that antimony could enhance production quality and efficiency in low-pressure die-cast copper alloys. Full article

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20 pages, 5115 KiB

Open AccessArticle

Gold Leaching from an Auriferous Ore by Alkaline Thiosulfate–Glycine–Copper Solution

by Alex S. Redrovan, Ernesto de la Torre and Carlos F. Aragón-Tobar

Metals 2025, 15(2), 204; https://doi.org/10.3390/met15020204 - 14 Feb 2025

Cited by 1 | Viewed by 1062

Abstract

The thiosulfate–glycine–copper system has emerged as a promising alternative for gold recovery, offering significant advantages over cyanidation and ammoniacal thiosulfate leaching. Recognizing the limitations of thiosulfate degradation in ammoniacal systems, this study focused on optimizing the thiosulfate–glycine–copper system for gold recovery using an [...] Read more.

The thiosulfate–glycine–copper system has emerged as a promising alternative for gold recovery, offering significant advantages over cyanidation and ammoniacal thiosulfate leaching. Recognizing the limitations of thiosulfate degradation in ammoniacal systems, this study focused on optimizing the thiosulfate–glycine–copper system for gold recovery using an auriferous ore with (10 g t⁻¹) of Au. The ore was associated with aluminosilicates such as grossular (64%) and clinochlore (12%). Leaching conditions were systematically varied, including thiosulfate (0.5–1 M), glycine (0.3–1.75 M), copper sulfate (2–10 mM), pH (9.3–10.5), temperature (20–60 °C), 6 h, and potassium permanganate concentrations (0.004–0.04 M), and dosing intervals were also optimized. Thus, the best conditions were thiosulfate (0.7 M), glycine (1.75 M), copper sulfate (5 mM), pH 9.3, 60 °C, and permanganate addition every 2 h. This system achieved 89.3% gold recovery in just 6 h, comparable to cyanidation (89.8% in 24 h) and ammoniacal thiosulfate (58% in 6 h), but without generating toxic effluents, such as in the cyanidation process. Additionally, a gold dissolution mechanism was proposed, highlighting glycine’s role in stabilizing cupric ions and enhancing thiosulfate efficiency. This study underscores the thiosulfate–glycine–copper system as a sustainable and effective method for gold recovery. Full article

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

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14 pages, 5744 KiB

Open AccessArticle

Effect of Multi-Phase Composite Structure on the Mechanical Properties of Al_xFe_1.5CoNiC_0.12 High Entropy Alloys

by Yiteng Jiang, Aoxiang Li, Kaiwen Kang, Jinshan Zhang, Di Huang, Chunning Che, Saike Liu, Mingkun Xu, Yaqing Li, Borui Zhang and Gong Li

Metals 2025, 15(2), 203; https://doi.org/10.3390/met15020203 - 14 Feb 2025

Viewed by 504

Abstract

Single-phase high entropy alloys (HEAs) exhibit limited mechanical properties while dual-phase and multi-phase HEAs offer better strength, toughness, and stability. In this paper, the as-cast Al_xFe_1.5CoNiC_0.12 HEAs with triple-phase dendritic composite structure is studied, and the influence of [...] Read more.

Single-phase high entropy alloys (HEAs) exhibit limited mechanical properties while dual-phase and multi-phase HEAs offer better strength, toughness, and stability. In this paper, the as-cast Al_xFe_1.5CoNiC_0.12 HEAs with triple-phase dendritic composite structure is studied, and the influence of the composite structure on the mechanical properties is discussed. The interdendrite (ID) of this structure is composed of a uniformly distributed high-density ordered face-centered cubic structure (L1₂) precipitate phase and face-centered cubic (FCC) matrix, while the dendrite (DR) consists of an ordered body-centered cubic (B2) single-phase. The high density L1₂ precipitate phase leads to a higher hardness in the FCC+L1₂ dual-phase region compared to the B2 single-phase region. The decrease in Al content can greatly improve mechanical performance. The improvement was attributed to the higher volume fraction of the ID and the smaller particle size of the precipitates. The L1₂ phase nano-precipitates exhibit minimal lattice mismatch with the FCC matrix, thereby significantly enhancing the stability of the alloy at the nanoscale. This stability is reflected in the fracture morphology. Modulating the triple-phase dendritic composite structure effectively improves the mechanical properties of the alloy. Full article

(This article belongs to the Special Issue Advances in High-Entropy Alloys’ Microstructure, Properties and Preparation)

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14 pages, 7114 KiB

Open AccessArticle

Preparation of Ultrafine Spherical Al-Mg Alloy and Its Energy Release Characteristics in Explosives

by Junhui Liu, Jie Yao, Zichao Wang, Wei Liu, Jianxin Nie and Shi Yan

Metals 2025, 15(2), 202; https://doi.org/10.3390/met15020202 - 14 Feb 2025

Viewed by 565

Abstract

The substitution of aluminum powder with highly reactive ultrafine aluminum-based metal fuels has a significant impact on the energy release of aluminum-containing energetic materials because of their excellent energy density and combustion performances. A series of ultrafine spherical Al-Mg alloy fuels with different [...] Read more.

The substitution of aluminum powder with highly reactive ultrafine aluminum-based metal fuels has a significant impact on the energy release of aluminum-containing energetic materials because of their excellent energy density and combustion performances. A series of ultrafine spherical Al-Mg alloy fuels with different contents of magnesium were prepared by close-coupled gas atomization technology. The properties of Al-Mg alloy powders of 13~15 μm were tested by SEM, TG-DSC, and laser ignition experiments. Results show that alloying with magnesium can significantly enhance thermal oxidation and combustion performance, leading to more oxidation weight gains and higher combustion heat release. HMX-based castable explosives with the same content of Al and the novel Al-Mg alloy were made and tested. Results show that the detonation performances of HMX/Al-Mg alloy/HTPB are better than HMX/Al/HTPB. Compared to the HMX/Al/HTPB explosive, the detonation heat of HMX/ Al-Mg alloy/HTPB was increased by 200 kJ/kg, the energy release efficiency was enhanced from 80.55% to 83.19%, the detonation velocity was increased by 114 m/s, and the shock wave overpressure at 5 m was increased by 83%. This research provides a new type of composite metal fuel for improving the combustion performance of Al powder. Full article

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14 pages, 8230 KiB

Open AccessArticle

Refinement Mechanism of Ultrafine-Grained CP-Ti Fabricated via Equal-Channel Angular Pressing

by Yanxia Gu, Jinghua Jiang, Aibin Ma and Haoran Wu

Metals 2025, 15(2), 201; https://doi.org/10.3390/met15020201 - 14 Feb 2025

Viewed by 434

Abstract

Grains of commercially pure titanium (CP-Ti) can be refined via rotary-die equal-channel angular pressing (RD-ECAP) to meet higher application requirements. However, the grain refinement mechanism of CP-Ti during RD-ECAP has not been fully studied. Herein, CP-Ti was processed up to four passes by [...] Read more.

Grains of commercially pure titanium (CP-Ti) can be refined via rotary-die equal-channel angular pressing (RD-ECAP) to meet higher application requirements. However, the grain refinement mechanism of CP-Ti during RD-ECAP has not been fully studied. Herein, CP-Ti was processed up to four passes by RD-ECAP to obtain an ultrafine-grained structure. The microstructure evolution, refinement mechanism, and dynamic recrystallization (DRX) behavior was investigated by TEM and EBSD analysis. The results revealed that after two passes, banded structures with numerous LAGBs inside were detected, while after four passes, most grains were equiaxed with HAGBs and the average grain size was about 0.5 μm. The fraction of HAGBs reached 78.6% for the four-pass sample, which was higher than that of two-pass sample. The fraction of deformed grains declined and the proportion of recrystallized grains increased as the pass number increased from two to four. The misorientation gradient analysis showed that subgrains with LAGBs evolved into new grains with HAGBs gradually to generate ultrafine grains. The refinement mechanism of CP-Ti during RD-ECAP can be concluded as continuous DRX (CDRX). In addition, the relationship between DRX type and the processing conditions as well as stacking fault energies (SFEs) of metals was innovatively explored, providing a new approach for predicting microstructure. Full article

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11 pages, 14052 KiB

Open AccessArticle

Effect of Cr and Mo Substitution of Fe on Activation and Hydrogen Ab-/Desorption Properties of TiFe Hydrogen Storage Alloy

by Yuehai Li, Houqun Xiao, Minglong Zhong and Qingjun Chen

Metals 2025, 15(2), 200; https://doi.org/10.3390/met15020200 - 14 Feb 2025

Viewed by 516

Abstract

In this study, a series of quaternary TiFe-based alloys, Ti_1.05Fe_0.85Cr_0.1−xMo_x (x = 0, 0.03, 0.05, 0.07, 0.1), were designed to investigate the activation and hydrogen ab-/desorption properties of TiFe hydrogen storage alloys through the [...] Read more.

In this study, a series of quaternary TiFe-based alloys, Ti_1.05Fe_0.85Cr_0.1−xMo_x (x = 0, 0.03, 0.05, 0.07, 0.1), were designed to investigate the activation and hydrogen ab-/desorption properties of TiFe hydrogen storage alloys through the substitution of Fe with Cr and Mo. The incorporation of Cr and Mo significantly enhanced the activation performance of TiFe hydrogen storage alloys, enabling activation at room temperature. This improvement in activation was accompanied by the maintenance of a high maximum hydrogen storage capacity and an elevated effective hydrogen storage capacity. As the Mo content increased, the lattice parameters increased slightly, further boosting the activation performance and reducing the optimal operating temperature from 90 to 75 °C, which can be readily matched using the waste heat from fuel cells. The addition of Mo also resulted in a flatter hydrogen absorption plateau, making the hydrogen storage and release process more stable. Among the alloys, Ti_1.05Fe_0.85Cr_0.05Mo_0.05 exhibited the best performance, with a maximum hydrogen storage capacity of 2.00 wt.%, an effective hydrogen storage capacity of 1.81 wt.%, and a relatively flat hydrogen ab-/desorption plateau. After 200 cycles, the hydrogen storage capacity decreased by only 0.50%, indicating promising application prospects in related fields. Full article

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15 pages, 3253 KiB

Open AccessArticle

An Investigation on Li-Ion Battery Recycling via In Situ Alloying: Influence of Slag Composition on Li and F Evaporation

by Safoura Babanejad, Hesham Ahmed, Charlotte Andersson, Olga Rodríguez-Largo, Anton Andersson, Lorena Alcaraz and Félix A. López

Metals 2025, 15(2), 199; https://doi.org/10.3390/met15020199 - 14 Feb 2025

Viewed by 507

Abstract

The amount of waste Li-Ion Batteries (LIBs) is significantly growing. Therefore, scholars and industries are exploring efficient ways to recover their valuable elements. Meanwhile, steel production generates Fe-rich slag, which is often sold for construction purposes without fully utilizing its potential metal content. [...] Read more.

The amount of waste Li-Ion Batteries (LIBs) is significantly growing. Therefore, scholars and industries are exploring efficient ways to recover their valuable elements. Meanwhile, steel production generates Fe-rich slag, which is often sold for construction purposes without fully utilizing its potential metal content. Reusing this slag in LIB recycling allows simultaneous recovery of valuable elements from both waste LIBs and steel slag. This study investigates the pyrometallurgical recycling of Black Mass (BM) from a mixture of spent LIBs in the presence of Fe-rich slag (set based on Electric Arc Furnace (EAF) slag), with a focus on the evaporation of Li and F, the critical volatile elements in the BM, at 1500 °C. The effects of basicity (B2), MgO content, and flux amount on Li and F evaporation were studied using a central composite experimental design, showing that while the effects of MgO content and flux amount were insignificant, B2 had a linear effect on Li and a quadratic effect on F evaporation. Thermodynamic and viscosity calculations suggest that higher B2 improves ion mobility, facilitating the evaporation mechanism. However, for F, its dual role at different B2 levels leads to an evaporation trend different from that of Li. Keeping B2 within a midrange seems to balance Li evaporation efficiency while limiting F evaporation. Full article

(This article belongs to the Special Issue Recent Progress in Metal Extraction and Recycling)

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14 pages, 4570 KiB

Open AccessArticle

Investigation on Laser Weldability of a 2.1 GPa-Grade Hot Stamping Steel with Medium Carbon Content

by Jiming Huang, Xuekun Shang, Liejun Li and Zhiyuan Liang

Metals 2025, 15(2), 198; https://doi.org/10.3390/met15020198 - 13 Feb 2025

Viewed by 525

Abstract

This investigation aimed at evaluating the weldability of a 2.1 GPa-grade hot stamping steel (HSS) containing 0.40 wt.% carbon using laser butt welding. It is shown that the subject HSS can be properly joined by laser welding without welding defects, such as voids [...] Read more.

This investigation aimed at evaluating the weldability of a 2.1 GPa-grade hot stamping steel (HSS) containing 0.40 wt.% carbon using laser butt welding. It is shown that the subject HSS can be properly joined by laser welding without welding defects, such as voids and micro-cracks. The mechanical properties of joints before and after hot stamping were examined using cross-weld uniaxial tension and Vickers hardness, while microstructure was systematically characterized using optical microscopy and electron backscatter diffraction. The experimental results demonstrate that fresh martensite was formed in the weld nugget after welding, leading to a hardness much higher than that of the base metal. Nevertheless, such cross-weld microstructural heterogeneity was erased after hot stamping and low-temperature baking heat treatments, resulting in a uniform microstructure of lath martensite across the weld. As a result, the joint after hot stamping and baking exhibited an ultimate tensile strength of 2140 MPa and a total elongation of 12.03%, with the fracture occurring in the base metal. Such excellent mechanical properties of the joint demonstrate the great weldability of the present 2.1 GPa-grade HSS during laser welding. Full article

(This article belongs to the Special Issue Recent Advances in Microstructure and Mechanical Properties of High-Strength Steels)

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40 pages, 12596 KiB

Open AccessFeature PaperReview

A Review on the Additive Manufacturing of W-Cu Composites

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

Metals 2025, 15(2), 197; https://doi.org/10.3390/met15020197 - 13 Feb 2025

Viewed by 1052

Abstract

In recent years, W-Cu composite systems have become very interesting subjects due to good electrical and thermal conductivity, high-temperature strength, certain plasticity, and excellent radiation resistance. W-Cu composites are a very important class of materials in applications like PFM (plasma facing materials), functional [...] Read more.

In recent years, W-Cu composite systems have become very interesting subjects due to good electrical and thermal conductivity, high-temperature strength, certain plasticity, and excellent radiation resistance. W-Cu composites are a very important class of materials in applications like PFM (plasma facing materials), functional graded materials (FGM), electronic packaging materials, high-voltage electrical contacts, sweating materials, shaped charge liners, electromagnetic gun-rail materials, kinetic energy penetrators, and radiation shielding/protection. There is no possibility of forming a crystalline structure between these two materials. However, due to the unique properties these materials possess, they can be used by preparing them as a composite. Generally, W-Cu composites are prepared via the conventional powder metallurgy routes, i.e., sintering, hot pressing, hot isostatic pressing, isostatic cold pressing, sintering and infiltration, and microwave sintering. However, these processes have certain limitations, like the inability to produce bulk material, they are expensive, and their adoptability is limited. Here, in this review, we will discuss in detail the fabrication routes of additive manufacturing, and its current progress, challenges, trends, and associated properties obtained. We will also explain the challenges for the additive manufacturing of the composite. We will also compare W-Cu composites to other materials that can challenge them in terms of specific applications or service conditions. The solidification mechanism will be explained for W-Cu composites in additive manufacturing. Finally, we will conclude the progress of additive manufacturing of W-Cu composites to date and suggest future recommendations based on the current challenges in additive manufacturing. Full article

(This article belongs to the Section Welding and Joining)

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12 pages, 2936 KiB

Open AccessArticle

Unveiling Irreversible β-Relaxations in Metallic Glasses via Electrical Resistivity

by Jianyu Chen, Shuai Ren, Zhe Chen, Jie Dong, Lixing Zhu, Yangguang Zhan, Wenxue Wang, Shenghao Zeng, Jing Xiao, Xiong Liang and Jiang Ma

Metals 2025, 15(2), 196; https://doi.org/10.3390/met15020196 - 13 Feb 2025

Viewed by 498

Abstract

Dynamic relaxations play an important role in understanding the nature of glass. The conventional methods to explore dynamic relaxations rely on the measurement of mechanical and thermic properties, while new methods that may provide a new perspective to probe dynamic relaxation are desperately [...] Read more.

Dynamic relaxations play an important role in understanding the nature of glass. The conventional methods to explore dynamic relaxations rely on the measurement of mechanical and thermic properties, while new methods that may provide a new perspective to probe dynamic relaxation are desperately required. Here, we show that the β-relaxation of metallic glasses (MGs) can be unveiled by electrical resistivity (ER). Irreversible β-relaxation leads to an increment in electrical resistivity, which can be fitted by the Kohlrausch–Williams–Watts equation well. In contrast, the ER results of the initialized sample only exhibit a negligible change during annealing, which indicates that the reversible β-relaxation change cannot be manifested by ER testing. This work provides the ER measurement as a new means to explore the dynamic relaxation of MGs, which may offer a new insight into the understanding of β-relaxation in glass materials. Full article

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19 pages, 5751 KiB

Open AccessArticle

Effect of the Use of Some Rare Earth Compounds as Corrosion Inhibitors for API 5L X70 Steel in Saline Medium

by Salvador Hernández García, Araceli Espinoza Vázquez, Laura Nadxieli Palacios-Grijalva, Anatolio Martínez Jiménez, Francisco Javier Rodríguez Gómez, Óscar Armando Gómez Vargas, Alan Miralrio, Miguel Castro and Ricardo Orozco Cruz

Metals 2025, 15(2), 195; https://doi.org/10.3390/met15020195 - 13 Feb 2025

Viewed by 637

Abstract

This work presents a comparative study of five rare earth compounds—Erbium nitrate pentahydrate lll (Er), Neodymium nitrate pentahydrate (Nd), Samarium III Nitrate Hexahydrate (Sm), Yterbium III Chloride Hexahydrate (Yb) and Praseodymium nitrate hexahydrate lll (Pr)—protecting API 5L X70 steel from corrosion in saline [...] Read more.

This work presents a comparative study of five rare earth compounds—Erbium nitrate pentahydrate lll (Er), Neodymium nitrate pentahydrate (Nd), Samarium III Nitrate Hexahydrate (Sm), Yterbium III Chloride Hexahydrate (Yb) and Praseodymium nitrate hexahydrate lll (Pr)—protecting API 5L X70 steel from corrosion in saline medium that uses electrochemical impedance spectroscopy (EIS) and polarization curves (CPs) at different concentrations and in static mode. The results show that Erbium is the best corrosion inhibitor, containing 50 ppm and reaching an inhibition efficiency of about 89%, and similar result was shown by Sm with an IE~87.9%, while the other rare earths (Nd, Yb and Pr) showed a decrease in corrosion protection at the same concentration, since they were below an IE~80%. On the other hand, with the Langmuir model it was possible to describe that the adsorption process of the three rare earths follows a combined physisorption–chemisorption process to protect the metal’s surface. The observed adsorption free energy, ΔG°ads, reaches −38.7 kJ/mol for Er, −34.4 kJ/mol for Nd, and −33.6 kJ/mol for Pr; whereas Sm and Yb have adsorption free energies of −33.9 and −35.0 kJ/mol, respectively. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) further confirmed the formation of a protective film. Their characterization using density functional theory showed the transference of charge from the iron cluster towards the rare earth metal compounds. The adsorption process produced a slightly polarized region of interaction with the metal surface. Also, it was found that the adsorption of the rare earths affected the magnetic properties of the surface of the iron cluster. Quantum chemical descriptors, such as Pearson’s HSAB (Hard and Soft Acids and Bases) descriptors, were useful in predicting the behavior of the flow of electrons between the metal surface and the interacting rare earth ions. Full article

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

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28 pages, 11553 KiB

Open AccessArticle

Characterization of High-Speed Steels—Experimental Data and Their Evaluation Supported by Machine Learning Algorithms

by Manfred Wiessner and Ernst Gamsjäger

Metals 2025, 15(2), 194; https://doi.org/10.3390/met15020194 - 12 Feb 2025

Viewed by 521

Abstract

X-ray diffractograms of high-speed steels are analyzed using machine learning algorithms to accurately classify various heat treatments. These differently heat-treated steel samples are also investigated by dilatometric analysis and by metallographic analysis in order to label the samples accordingly. Both agglomerative hierarchical clustering [...] Read more.

X-ray diffractograms of high-speed steels are analyzed using machine learning algorithms to accurately classify various heat treatments. These differently heat-treated steel samples are also investigated by dilatometric analysis and by metallographic analysis in order to label the samples accordingly. Both agglomerative hierarchical clustering and t-distributed stochastic neighbor embedding are employed to automatically classify preprocessed X-ray datasets. The clusters obtained by this procedure agree well with the labeled data. By supervised learning via a support vector machine, hyperplanes are constructed that allow separating the clusters from each other based on the X-ray measurements. The exactness of these hyperplanes is analyzed by cross-validation. The machine learning algorithms used in this work are valuable tools to separate different microstructures based on their diffractograms. It is demonstrated that the separation of martensitic, bainitic, and pearlitic microstructures is possible based on the diffractograms only by means of machine learning algorithms, while the same problem is error-prone when looking at the diffractograms only. Full article

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