Metals

19 pages, 5617 KiB

Open AccessArticle

Effect of Leaching on Particle Migration and Pore Structure of Ionic Rare Earth Ores with Different Fine Particle Contents

by Yunzhang Rao, Jiazheng Wan, Shujun Tan, Zhihua Yang, Guozhu Rao, Qiang Huang, Yangjun Xie and Qiande Lai

Metals 2025, 15(4), 396; https://doi.org/10.3390/met15040396 - 1 Apr 2025

Abstract

In in situ leaching, fine particles can be stripped and transported with the leach solution, significantly altering the particle size distribution and pore structure of each layer of the rare earth ore body. In this study, water and magnesium sulfate were used as [...] Read more.

In in situ leaching, fine particles can be stripped and transported with the leach solution, significantly altering the particle size distribution and pore structure of each layer of the rare earth ore body. In this study, water and magnesium sulfate were used as leaching agents. Based on indoor column leaching experiments, particle gradation experiments, and pore structure tests, this study investigates and analyzes the patterns of particle migration and changes in pore structure in rare earth ores with varying fine particle contents under leaching conditions. The results indicate that during the leaching process, the degree of change in particle gradation follows the order of upper layer > middle layer > lower layer. As the depth increases, the soil becomes denser, leading to reduced permeability, a slower seepage rate of the leaching solution, and a higher fine particle content, making the effect more pronounced. During magnesium sulfate leaching, the overall trend of porosity in the rare earth ore structure initially increases and then decreases. Additionally, a higher fine particle content corresponds to higher porosity. In the early and late stages of leaching, pore size changes involve the transformation of larger pores into smaller ones, followed by the conversion of smaller pores into larger ones. Moreover, the higher the fine particle content, the greater the degree of transformation between the pore sizes. Full article

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16 pages, 4993 KiB

Open AccessArticle

Rapid Microwave Irradiation-Enhanced Detoxification and Mineralization of Cr(VI) by FeS₂/ZVI Composites

by Xiaoming Zhang, Haiying Wang, Mengying Si, Qi Liao, Zhihui Yang, Qi Li and Weichun Yang

Metals 2025, 15(4), 395; https://doi.org/10.3390/met15040395 - 1 Apr 2025

Abstract

The rapid detoxification and mineralization of Cr(VI) in aqueous environments hold critical importance for emergency response and resource recovery yet remain technically challenging. Herein, we report the synthesis of FeS₂/ZVI composites through ethanol-assisted wet ball-milling and their application in Cr(VI) removal [...] Read more.

The rapid detoxification and mineralization of Cr(VI) in aqueous environments hold critical importance for emergency response and resource recovery yet remain technically challenging. Herein, we report the synthesis of FeS₂/ZVI composites through ethanol-assisted wet ball-milling and their application in Cr(VI) removal under microwave (MW) irradiation. This study systematically investigates the effects of MW irradiation on the removal efficiency of Cr(VI) using FeS₂/ZVI composites, with particular focus on key parameters including composite dosage, initial pH, MW temperature, and Cr(VI) concentration. Notably, 1 g/L FeS₂/ZVI composites achieved near-complete removal (>99%) of 50 mg/L Cr(VI) within 7 min at a MW irradiation temperature of 333 K, which exhibited 5.9-fold and 13.1-fold superior performance compared to pure pyrite and ZVI, respectively. Additionally, there is a 96.1% reduction in reaction time in comparison to non-MW irradiation system. In real electroplating wastewater samples, Cr(VI) concentration was reduced from 38.93 to 0.42 mg L⁻¹ by MW irradiation-assisted treatment, validating its potential for practical applications in industrial Cr(VI) pollution control. The activation energy determined by fitting the Arrhenius equation showed a 39.7% reduction for the MW-assisted FeS₂/ZVI system (16.0 kJ mol⁻¹) compared to conventional thermal heating (from 25.6 kJ mol⁻¹), indicating that MW irradiation induced catalytic enhancement of FeS₂/ZVI, thereby lowering the energy barrier for Cr(VI) reduction. Moreover, MW irradiation-assisted processes facilitated the mineralization of reduced Cr(III) to stable spinel FeCr₂O₄. These findings collectively establish a synergistic mechanism between MW activation and FeS₂/ZVI composites, offering innovative pathways for efficient Cr(VI) detoxification and resource recovery from high-strength industrial wastewaters. Full article

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26 pages, 6349 KiB

Open AccessArticle

Upset Resistance Welding of a Microcomposite Cu-Nb Conductor for Pulsed Power Applications

by Nikolaj Višniakov, Paulius Beinoras and Oleksandr Kapustynskyi

Metals 2025, 15(4), 394; https://doi.org/10.3390/met15040394 - 1 Apr 2025

Abstract

The present study offers an experimental investigation into the welding of Cu–Nb wire using upset resistance welding. The aim is to examine the structure, as well as the electrical and mechanical properties, of Cu–Nb conductor joints produced by this method, which are intended [...] Read more.

The present study offers an experimental investigation into the welding of Cu–Nb wire using upset resistance welding. The aim is to examine the structure, as well as the electrical and mechanical properties, of Cu–Nb conductor joints produced by this method, which are intended for use in coils in pulsed magnetic systems. Analysis of the joint structure revealed that it was free from welding defects. The welded joint demonstrated a negligible change in electrical resistance while retaining sufficient ultimate strength and plasticity comparable to the base material. The tensile strength of the welded sample was found to be 620 MPa. The heat-affected zone is narrow, and the heating temperature is lower than the melting point of the composite material. Therefore, welding occurs in the solid phase without remelting the Cu–Nb composite wire or destroying its unique microstructure. Thus, upset welding is a promising technology for use in solenoid terminal connections with external electrical circuits that are not directly exposed to the high magnetic or tensile forces generated inside a solenoid of a pulsed magnet system. Full article

(This article belongs to the Section Welding and Joining)

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17 pages, 16960 KiB

Open AccessArticle

Effect of Laser Welding on Performance of the B1500HS/340LA High-Strength Steel

by Heyuan Wang, Yongchuan Duan, Shijun Hao and Yingping Guan

Metals 2025, 15(4), 393; https://doi.org/10.3390/met15040393 - 1 Apr 2025

Abstract

In this study, high-strength steels B1500HS and B340LA were used as base materials, and laser welding experiments were conducted within a parameter range of welding power from 1500 W to 3000 W and welding speed from 15 mm/s to 35 mm/s. Microstructural analysis, [...] Read more.

In this study, high-strength steels B1500HS and B340LA were used as base materials, and laser welding experiments were conducted within a parameter range of welding power from 1500 W to 3000 W and welding speed from 15 mm/s to 35 mm/s. Microstructural analysis, microhardness testing, and uniaxial tensile tests were performed to systematically investigate the effects of different welding parameters on the weld microstructure and macroscopic mechanical properties, leading to the identification of an optimal welding parameter range that avoids defect-prone regions. The bending formability of tailor-welded blanks (TWBs) was evaluated using hat-shaped bending tests, with finite element simulations employed to analyze the effects of welding parameters on stress distribution and material hardening behavior. Based on the identified high-quality welding parameters, a suitable welding parameter range for reverse bending conditions was determined, effectively improving the bending formability of TWBs and providing theoretical guidance and experimental support for their engineering applications. Full article

(This article belongs to the Section Welding and Joining)

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22 pages, 17592 KiB

Open AccessArticle

Impact of Feature-Selection in a Data-Driven Method for Flow Curve Identification of Sheet Metal

by Quang Ninh Hoang, Hyungbum Park, Dang Giang Lai, Sy-Ngoc Nguyen, Quoc Tuan Pham and Van Duy Dinh

Metals 2025, 15(4), 392; https://doi.org/10.3390/met15040392 - 31 Mar 2025

Abstract

This study presents an innovative data-driven methodology to model the hardening behavior of sheet metals across a broad strain range, crucial for understanding sheet metal mechanics. Conventionally, true stress–strain data from such tests are used to analyze plastic flow within the pre-necking regime, [...] Read more.

This study presents an innovative data-driven methodology to model the hardening behavior of sheet metals across a broad strain range, crucial for understanding sheet metal mechanics. Conventionally, true stress–strain data from such tests are used to analyze plastic flow within the pre-necking regime, often requiring additional experiments to inverse finite element methods, which demand extensive field data for improved accuracy. Although digital image correlation offers precise data, its implementation is costly. To address this, we integrate experimental data from standard tensile tests with a machine-learning approach to estimate the flow curve. Subsequently, we conduct finite element simulations on uniaxial tensile tests, using materials characterized by the Swift constitutive equation to build a comprehensive database. Loading force-gripper displacement curves from these simulations are then transformed into input features for model training. We propose and compare three models—Models A, B, and C—each employing different input feature selections to estimate the flow curve. Experimental validation including uniaxial tensile, plane strain, and simple shear tests on the DP590 and DP780 sheets are then carefully considered. Results demonstrate the effectiveness of our proposed method, with Model C showing the highest efficacy. Full article

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

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13 pages, 5508 KiB

Open AccessArticle

The Effect of Al Loss on the Microstructural Formation of TiAl Alloys Produced via Direct Laser Deposition

by Xinyu Zhang, Chuanwei Li and Jianfeng Gu

Metals 2025, 15(4), 391; https://doi.org/10.3390/met15040391 - 31 Mar 2025

Abstract

Additive manufacturing is becoming a popular and effective process for lightweight high-temperature TiAl alloys, but there is a lack of understanding regarding the corresponding microstructural formation mechanisms. In this study, various Ti-47Al-2Cr-2Nb alloys were additively manufactured with different laser power values, and the [...] Read more.

Additive manufacturing is becoming a popular and effective process for lightweight high-temperature TiAl alloys, but there is a lack of understanding regarding the corresponding microstructural formation mechanisms. In this study, various Ti-47Al-2Cr-2Nb alloys were additively manufactured with different laser power values, and the related microstructures were carefully characterized. The results show that a convoluted microstructure, a nearly full α₂/γ lamellar structure, and an α₂/β Widmanstatten structure were obtained as the laser power was increased. Moreover, the Al content of the as-deposited specimen decreased from 47 at.% to 40 at.%, which is considered to have strongly affected microstructural formation. As the Al content decreased, the solidified microstructure transformed from hexagonal dendritic α₂ to orthogonal dendritic β and cellular β, successively. Moreover, massive α → γ transformation is more likely when the Al content is high, and α → α₂ transformation tends to occur when the Al content decreases. The microstructure evolution processes are evaluated in the present paper by synthesizing the experimental results with a thermodynamics analysis. Full article

(This article belongs to the Section Additive Manufacturing)

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14 pages, 2376 KiB

Open AccessArticle

Electrochemical Evaluation of Strontium-Doped Micro-Arc Oxidation Surfaces on Titanium

by Alexandra C. Alves, Carolina Durães and Fatih Toptan

Metals 2025, 15(4), 390; https://doi.org/10.3390/met15040390 - 31 Mar 2025

Abstract

Titanium (Ti) alloys are widely used in biomedical applications but face challenges like poor biological activity and corrosion at modular interfaces. Strontium (Sr)-doped micro-arc oxidation (MAO) surfaces are proposed to improve biocompatibility and tribocorrosion resistance. This study examines the electrochemical behaviour of Ti [...] Read more.

Titanium (Ti) alloys are widely used in biomedical applications but face challenges like poor biological activity and corrosion at modular interfaces. Strontium (Sr)-doped micro-arc oxidation (MAO) surfaces are proposed to improve biocompatibility and tribocorrosion resistance. This study examines the electrochemical behaviour of Ti surfaces treated with 0.0013 M and 0.13 M Sr-doped MAO via open circuit potential, potentiodynamic polarisation, and electrochemical impedance spectroscopy in a basic physiological solution at 37 °C. The results indicate that higher Sr concentrations led to lower passivation current densities (more than two times lower than at the lowest Sr concentration) and reduced barrier layer capacitance (more than one and a half times lower than at the lowest Sr concentration), suggesting improved corrosion resistance for Sr-enriched MAO treatments on Ti implants. Full article

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

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15 pages, 8928 KiB

Open AccessArticle

Aging Behavior of 10CrNi2Mo3Cu2V Maraging Alloy: Clustering, Precipitation, and Strengthening

by Jiqing Zhao, Gang Yang and Zhihua Gong

Metals 2025, 15(4), 389; https://doi.org/10.3390/met15040389 - 30 Mar 2025

Abstract

The high-temperature performance of 10CrNi2Mo3Cu2V steel is critically governed by the distribution of Cu-rich phases. This study systematically investigated the evolution of solute redistribution, Cu-rich phase precipitation, microstructural transformations, and mechanical properties in 10CrNi2Mo3Cu2V alloy under varying aging temperatures. Advanced characterization techniques, including [...] Read more.

The high-temperature performance of 10CrNi2Mo3Cu2V steel is critically governed by the distribution of Cu-rich phases. This study systematically investigated the evolution of solute redistribution, Cu-rich phase precipitation, microstructural transformations, and mechanical properties in 10CrNi2Mo3Cu2V alloy under varying aging temperatures. Advanced characterization techniques, including atom probe tomography (APT) and transmission electron microscopy (TEM), were employed to analyze microstructural features and phase formation in both as-built and heat-treated specimens. The key findings reveal that copper atom segregation initiates at a tempering temperature of 350 °C. Upon increasing the temperature to 450 °C, extensive precipitation of nanoscale copper clusters is observed. Temperatures exceeding 450 °C trigger the formation of ε-Cu phases, which undergo subsequent coarsening. Notably, these copper clusters and Cu-rich precipitates act as dislocation pinning sites, promoting crack nucleation and propagation, thereby markedly degrading the alloy’s impact energy absorption capacity. The critical diameter for Orowan mechanism-governed strengthening by Cu-rich phases is determined to be ~6 nm, while the average diameter of matrix-penetrating Cu-rich particles is approximately 1.46 nm. Quantitative analysis demonstrated that the combined contributions of the Orowan bypass mechanism and particle-cutting mechanism yield a strength enhancement of ~219 MPa, which exhibits excellent agreement with experimentally measured strength increments. These results provide critical insights into the interplay between microstructural evolution and mechanical degradation in precipitation-strengthened steels under thermal exposure. Full article

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

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15 pages, 30326 KiB

Open AccessArticle

Effects of Cr and Al Contents on the Oxide Structures of Ni-Based Superalloys at High Temperatures

by Kwangsoo Choi, Byunghak Choe, Sunghee Han, Daehyun Kim, Seong-Moon Seo and Dae Won Yun

Metals 2025, 15(4), 388; https://doi.org/10.3390/met15040388 - 29 Mar 2025

Abstract

In this study, the morphology of high-temperature surface oxides in Ni-based superalloys was investigated as a function of Cr and Al content. First, the oxide layer morphologies of various alloys published in the literature were classified according to the basic model of Cr [...] Read more.

In this study, the morphology of high-temperature surface oxides in Ni-based superalloys was investigated as a function of Cr and Al content. First, the oxide layer morphologies of various alloys published in the literature were classified according to the basic model of Cr and Al content. Then, the high-temperature oxide layers of high-Cr/low-Al and low-Cr/high-Al alloys were investigated using SEM/EDX mapping. The high-temperature oxidation of Ni-based superalloys is affected by the amount of added elements such as Ti, Cr, and Al. The oxidation rate of each element is NiO > TiO₂ > Cr₂O₃ > Al₂O₃, and the shape of the surface oxide layer is determined by the oxidation rate. The oxide layer is mainly classified according to the flat and fibrous shapes of Cr₂O₃ and Al₂O₃ on the outermost layer. In this study, IN738LC and IN792, as the high Cr-low Al alloys, were found to have flat Cr₂O₃ and fibrous type Al₂O₃ in the outermost layer after long-term exposure to high temperatures, while CM247LC and CMSX4 which are the low Cr-high Al alloys were found to have flat type Al₂O₃ in the outermost layer after long-term exposure to high temperatures, which is in good agreement with the results of various literature on oxide layers on Ni-based superalloys. Full article

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14 pages, 3644 KiB

Open AccessArticle

Graphene Doped with Transition Metal Oxides: Enhancement of Anode Performance in Lithium-Ion Batteries

by Jun Du, Liwei Liao, Binbin Jin, Xinyi Shen, Zhe Mei, Qingcheng Du, Hailin Nong, Bingxin Lei and Liying Liang

Metals 2025, 15(4), 387; https://doi.org/10.3390/met15040387 - 29 Mar 2025

Abstract

In recent years, transition metal oxides (TMOs) have emerged as promising candidates for anode materials in lithium-ion batteries (LIBs) owing to their high theoretical capacities. Regrettably, most TMOs exhibit poor electronic/ionic conductivity and undergo substantial volume expansion during the lithiation/delithiation processes. In this [...] Read more.

In recent years, transition metal oxides (TMOs) have emerged as promising candidates for anode materials in lithium-ion batteries (LIBs) owing to their high theoretical capacities. Regrettably, most TMOs exhibit poor electronic/ionic conductivity and undergo substantial volume expansion during the lithiation/delithiation processes. In this study, an electrostatic spinning method using polyacrylonitrile, graphene, and iron(III) acetylacetonate as precursors was employed to synthesize the Fe₃O₄@G/C composite through carbon coating and graphene doping. The composition, phase structure, and morphology of the Fe₃O₄@G/C composite were thoroughly investigated. The electrochemical performance of the Fe₃O₄@G/C composite as a lithium-ion battery anode was evaluated through a continuous charge–discharge cycling test. After 100 cycles at a current density of 0.1 A/g, the specific capacity of the Fe₃O₄@G/C material remained at 595.8 mAh/g. Additionally, the incorporation of graphene leads to a reduction in the electron orbital energy of Fe, which was verified by comparing the density of states (DOS) before and after the doping. Simultaneously, the electrochemical performance of CoO@G/C and NiO@G/C composites further demonstrates that doping transition metal oxides with graphene can enhance their performance as anodes for lithium-ion batteries. We anticipate that this design concept will open new avenues for the development of transition metal oxides (TMOs) and propel their adoption in practical applications. Full article

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25 pages, 4525 KiB

Open AccessReview

Advancement in Research on Silicon/Carbon Composite Anode Materials for Lithium-Ion Batteries

by Binbin Jin, Liwei Liao, Xinyi Shen, Zhe Mei, Qingcheng Du, Liying Liang, Bingxin Lei and Jun Du

Metals 2025, 15(4), 386; https://doi.org/10.3390/met15040386 - 29 Mar 2025

Abstract

Silicon stands out as an exceptionally viable anode material, distinguished by its substantial capacity, plentiful natural reserves, eco-friendliness, and favorable low working potential. Nonetheless, the material’s pronounced volume fluctuations readily induce particle fragmentation, detachment of active components, and repeated disruption of the solid [...] Read more.

Silicon stands out as an exceptionally viable anode material, distinguished by its substantial capacity, plentiful natural reserves, eco-friendliness, and favorable low working potential. Nonetheless, the material’s pronounced volume fluctuations readily induce particle fragmentation, detachment of active components, and repeated disruption of the solid electrolyte interphase (SEI) layer. These factors contribute to a shortened cycle life and rapid capacity fading, thus hindering its practical application. The carbon composite approach can efficiently counteract these issues by capitalizing on silicon’s high capacity and employing carbon as a cushioning agent to diminish volume swelling, thus enhancing the deployment of silicon-based anode materials. This paper offers an exhaustive examination of the lithiation processes involved in Si/C anodes and delves into the strategic utilization of diverse carbon materials, including graphite, graphene, graphdiyne, carbon nanotubes, carbon fibers, MXenes, pitch, heteroatom-doped polymers, biomass-derived carbon, carbon-containing gas-derived carbon, MOFs, and g-C₃N₄ to advance the application of silicon in lithium-ion battery (LIB) anodes. Overall, this paper concentrates on summarizing the current research status and technological advancement and juxtaposes the merits and demerits of various carbon sources in Si/C anodes, thus providing a comprehensive assessment and forward-looking perspective on their future development. Full article

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17 pages, 7796 KiB

Open AccessArticle

Influence of Nd:YAG Laser Melting on an Investment-Casting Co-Cr-Mo Alloy

by Francisco Cepeda Rodríguez, Carlos Rodrigo Muñiz Valdez, Juan Carlos Ortiz Cuellar, Jesús Fernando Martínez Villafañe, Jesús Salvador Galindo Valdés and Gladys Yerania Pérez Medina

Metals 2025, 15(4), 385; https://doi.org/10.3390/met15040385 - 29 Mar 2025

Abstract

The investment casting process, also known as lost-wax casting, is widely used for producing ferrous and non-ferrous metal parts due to its excellent surface finish and dimensional accuracy. In recent years, the use of Co-Cr-Mo alloy has increased due to its high corrosion [...] Read more.

The investment casting process, also known as lost-wax casting, is widely used for producing ferrous and non-ferrous metal parts due to its excellent surface finish and dimensional accuracy. In recent years, the use of Co-Cr-Mo alloy has increased due to its high corrosion resistance, good biocompatibility, and relatively high wear resistance. Laser melting of materials has been demonstrated to refine the surface grain structure, reduce surface roughness, and improve both wear and corrosion resistance. The ability to fine-tune parameters such as laser power density and scanning speed facilitates the optimization of the treated layers’ thickness and homogeneity, thereby addressing many of the shortcomings inherent in conventional methods. This study investigates the microstructural, mechanical wear and bioactive behavior of investment-cast Co-Cr-Mo parts subjected to a Nd:YAG laser surface treatment. The effects of different processing parameters were analyzed quantitatively and comprehensively. The specimens were characterized using metallographic techniques, bioactivity evaluation, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), wear testing (Pin-on-Disk), and hardness testing. Our results demonstrate that Nd:YAG laser melting significantly enhances the surface properties and maintains the dimensional accuracy of complex Co-Cr-Mo biomedical components, through microstructural refinement, increased hardness, improved wear resistance, and preserved biocompatibility. The specific combination of investment casting with precisely controlled laser surface modification represents a significant advancement for improving the longevity and performance of biomedical implants. Full article

(This article belongs to the Special Issue Manufacture, Mechanical Properties and Metallurgy of Metallic Biomaterials)

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12 pages, 11545 KiB

Open AccessArticle

Effect of Notches on Fatigue Crack Initiation and Early Propagation Behaviors of a Ni-Based Superalloy at Elevated Temperatures

by Zuopeng Zhao, Xuteng Hu and Zhiwei Guo

Metals 2025, 15(4), 384; https://doi.org/10.3390/met15040384 - 29 Mar 2025

Abstract

The role of notch stress and surface defects on fatigue crack initiation and small-crack propagation behavior has been investigated using groove simulation specimens. The naturally initiated small-crack growth tests have been performed on a FGH4099 superalloy at 500 °C and 700 °C. The [...] Read more.

The role of notch stress and surface defects on fatigue crack initiation and small-crack propagation behavior has been investigated using groove simulation specimens. The naturally initiated small-crack growth tests have been performed on a FGH4099 superalloy at 500 °C and 700 °C. The findings indicate that elevated testing temperature significantly reduced the proportion of fatigue crack initiation life, with a less pronounced effect on the proportion of life for cracks to grow to First Engineering Crack size. Competing crack initiation modes were observed in the fatigue test of groove simulation specimens. The location of maximum principal stress was dominant fatigue crack initiation sites, and for specimens with surface inclusions, the defect location can also serve as a crack initiation site. Furthermore, crack initiation modes were found to have a more pronounced effect on the small-crack growth rate. A turning point observed in the crack growth rate curves for specimens with multi-site crack initiation was attributed to crack shielding and subsequent coalescence. Full article

(This article belongs to the Special Issue Fatigue Assessment of Metals)

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24 pages, 10368 KiB

Open AccessArticle

The Effects of Alloying Elements on the Corrosion of Rebar Steel in a Chloride Environment

by Jing Yuan, Pei Li, Huanhuan Zhang, Shubiao Yin, Mingli Xu and Akun Zhou

Metals 2025, 15(4), 383; https://doi.org/10.3390/met15040383 - 28 Mar 2025

Abstract

The corrosion behaviors in chloride environment of two commercial low-alloy steel bars were studied. Through cyclic wetting tests, accelerated corrosion experiments ranging from 1 to 576 h were conducted on low-alloy bars and original bars. Techniques such as OM, SEM, EDS, AFM, and [...] Read more.

The corrosion behaviors in chloride environment of two commercial low-alloy steel bars were studied. Through cyclic wetting tests, accelerated corrosion experiments ranging from 1 to 576 h were conducted on low-alloy bars and original bars. Techniques such as OM, SEM, EDS, AFM, and XRD were employed to characterize the corrosion emergence and expansion behaviors of these bars in a simulated marine wetting and sun exposure environment. The designed low-alloy corrosion-resistant rebar achieved a 500 MPa yield strength. In each corrosion cycle, its corrosion loss and rate were lower than those of same-strength ordinary rebars. Analysis of the rust layer’s macro and micro morphology and alloy element distribution revealed alloy elements had little effect at corrosion initiation. In later corrosion, their enrichment led to a denser rust layer, effectively blocking corrosion expansion and chloride salt infiltration. After 72 h of accelerated corrosion, the corrosion rate growth of both bars slowed. The inner rust layer’s electrochemical potential increased, and local corrosion pits turned into uniform corrosion. The inner rust layer of the rebar formed more stable chromic acid with ionic compounds, reducing corrosion sensitivity. This study offers insights into steel bar corrosion and alloy element roles, guiding the preparation of low-alloy corrosion-resistant steel bars. Full article

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

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15 pages, 7943 KiB

Open AccessArticle

The Effect of He on the Evolution of Radiation-Induced Dislocation Loops Near W/Cu Interface

by Huaqing Sang, Yifan Zhang and Jing Wang

Metals 2025, 15(4), 382; https://doi.org/10.3390/met15040382 - 28 Mar 2025

Abstract

In the current work, the distribution behaviors of irradiation-induced dislocation loops near the W-Cu interface (contains a thin W₂C transition layer) under self-interstitial atom diffusion-dominated conditions were investigated based on the comparative experiment of 3 MeV Fe ion and 100 keV [...] Read more.

In the current work, the distribution behaviors of irradiation-induced dislocation loops near the W-Cu interface (contains a thin W₂C transition layer) under self-interstitial atom diffusion-dominated conditions were investigated based on the comparative experiment of 3 MeV Fe ion and 100 keV He ion irradiation. The size distribution and number density of radiation-induced dislocation loops in both sides of the interface were characterized using Transmission Electron Microscopy with different two-beam conditions. The impact of the phase boundary on the dislocation loop distribution and the influence of He on this mechanism was discussed. The results showed that the phase boundary (PB) has a significant effect on the distribution of radiation-induced dislocation loops. In the Fe-irradiated sample, the proportion of b = 1/2<111> type dislocation loops near the phase boundary on the W side increases significantly, and b = 1/2<110> type dislocation loops dominate on the Cu side. He will significantly affect the loop distribution near the W/Cu phase boundary due to the strong binding of He with vacancies in W, which suppresses the recombination of SIA and vacancies and promotes the formation and growth of interstitial-type dislocations. Full article

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10 pages, 11069 KiB

Open AccessCommunication

Investigation of High-Temperature Tensile Properties and Fracture Mechanisms of GH3536 Alloy Fabricated by Selective Laser Melting

by Biao Zhou, Shuai Huang, Tianyuan Wang, Cheng Wang and Bingqing Chen

Metals 2025, 15(4), 381; https://doi.org/10.3390/met15040381 - 28 Mar 2025

Abstract

This work revealed the mechanism of microstructure evolution on tensile properties in selective laser melted (SLM) GH3536 superalloys in the range of room temperature to 1000 °C. The results showed that SLM-GH3536 alloy exhibited isotropic tensile properties along X, Z, and 45° directions. [...] Read more.

This work revealed the mechanism of microstructure evolution on tensile properties in selective laser melted (SLM) GH3536 superalloys in the range of room temperature to 1000 °C. The results showed that SLM-GH3536 alloy exhibited isotropic tensile properties along X, Z, and 45° directions. The carbide at the grain boundary changed from banded to granular, resulting in a significant decrease in tensile strength at elevated temperatures, and the fracture mode transitioned from a mixed fracture to transgranular fracture. Full article

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16 pages, 3415 KiB

Open AccessArticle

Catalytic Properties of ZnZrO_x Obtained via Metal–Organic Framework Precursors for CO₂ Hydrogenation to Prepare Light Olefins

by Rundong Cai, Heping Zheng, Hong Liang, Xiankun Chen and Jianhua Tang

Metals 2025, 15(4), 380; https://doi.org/10.3390/met15040380 - 28 Mar 2025

Abstract

The conversion of CO₂ into light olefins over bifunctional catalysts is a promising route for producing high-value-added products. This approach not only mitigates excessive CO₂ emissions but also reduces the chemical industry’s reliance on fossil fuels. Among bifunctional catalysts, ZnZrO_x [...] Read more.

The conversion of CO₂ into light olefins over bifunctional catalysts is a promising route for producing high-value-added products. This approach not only mitigates excessive CO₂ emissions but also reduces the chemical industry’s reliance on fossil fuels. Among bifunctional catalysts, ZnZrO_x is widely used due to its favorable oxide composition. In this work, ZnZrO_x solid solution was synthesized by calcining an MOF precursor, resulting in a large specific surface area and a small particle size. Characterization studies revealed that ZnZrO_x prepared via MOF calcination exhibited an enhanced CO₂ activation and H₂ dissociation capacity compared to that synthesized using the co-precipitation method. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that CO₂ adsorption on ZnZrO_x led to the formation of carbonate species, while HCOO* and CH₃O* intermediates were generated upon exposure to the reaction gas. When ZnZrO_x was combined with SAPO-34 molecular sieves under reaction conditions of 380 °C, 3 MPa, and 6000 mL·g_cat⁻¹·h⁻¹, the CO₂ conversion reached 34.37%, with a light olefin yield of 15.13%, demonstrating a superior catalytic performance compared to that of the co-precipitation method. Full article

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12 pages, 6050 KiB

Open AccessArticle

Effects of Fine Cu Particle Size on Sinter-Bondability in Die Bonding Using Cu Paste Possessing Effective Reducing Formulation

by Horyun Kim and Jong-Hyun Lee

Metals 2025, 15(4), 379; https://doi.org/10.3390/met15040379 - 28 Mar 2025

Abstract

The application of wide-bandgap semiconductors in next-generation power modules requires cost-effective Cu particles and a reduced bonding time in the die attachment process to enable efficient industrial-scale manufacturing. Therefore, this study aimed to analyze the effect of Cu particle size variation on pressure-assisted [...] Read more.

The application of wide-bandgap semiconductors in next-generation power modules requires cost-effective Cu particles and a reduced bonding time in the die attachment process to enable efficient industrial-scale manufacturing. Therefore, this study aimed to analyze the effect of Cu particle size variation on pressure-assisted sinter-bondability and bond line shear strength. Cu particles were synthesized through a simple wet-chemical process, in which pH variation was employed to obtain submicrometer-sized Cu particles with average diameters of 500, 300, and 150 nm. The synthesized particles exhibited pure Cu composition, forming only a native oxide layer on their surfaces. In pastes containing these Cu particles, smaller particle sizes led to the delayed evaporation of the reducing solvent, which in turn delayed the exothermic reactions associated with particle sintering and oxidation. However, the sintering-induced exothermic peak became more pronounced as the particle size decreased, confirming that smaller particles improved sinterability. Pressure-assisted sinter bonding performed in air at 300 °C indicated that a decreased particle size contributed to the densification of the bond line structure and an increase in shear strength. Specifically, the paste containing 150 nm Cu particles achieved a highly dense microstructure and an exceptional shear strength of 36.7 MPa within just 30 s of sinter bonding. These findings demonstrate that reducing the particle size is essential for enhancing the sinter-bondability of cost-effective Cu particle-based sinter-bonding pastes. Full article

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49 pages, 2136 KiB

Open AccessReview

History of Metallic Orthopedic Materials

by Elia Marin and Alex Lanzutti

Metals 2025, 15(4), 378; https://doi.org/10.3390/met15040378 - 28 Mar 2025

Abstract

The history of metallic orthopedic materials spans a few centuries, from the use of carbon steel to the widespread adoption of titanium and its alloys. This paper explores the evolution of these materials, emphasizing their mechanical properties, biocompatibility, and the roles that they [...] Read more.

The history of metallic orthopedic materials spans a few centuries, from the use of carbon steel to the widespread adoption of titanium and its alloys. This paper explores the evolution of these materials, emphasizing their mechanical properties, biocompatibility, and the roles that they have played in improving orthopedic care. Key developments include the discovery of titanium’s osseointegration capability, the advent of porous coatings for osseointegration, surface modifications, and the rise of additive manufacturing for patient-specific implants. Beyond titanium, emerging materials such as biodegradable alloys, tantalum, zirconium, and amorphous metals are creating a completely new field of application for orthopedic metals. These innovations address longstanding challenges, including stress shielding, corrosion, and implant longevity, while leading the way for bioresorbable and 3D-printed patient-specific solutions. This paper concludes by examining future trends and their potential for industrial application. By understanding the historical developments in metallic orthopedic materials, this review highlights how past advancements have laid the foundation for both current and future innovations, guiding research towards solutions that better mimic the properties of biological tissues, offer higher reliability in vivo, and enable patient-specific treatments. Full article

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