Materials

11 pages, 2847 KB

Open AccessArticle

In Situ Observation of Deformation in a Sn-3Ag-0.5Cu/Cu Solder Joint Using High-Voltage Transmission Electron Microscopy

by Kazuhiro Nogita, Xin Fu Tan, Jiye Zhou, Stuart D. McDonald, Keith Sweatman, Flora Somidin, Guang Zeng, Hiroshi Maeno, Kazuhiro Yasuda and Christopher M. Gourlay

Materials 2025, 18(16), 3925; https://doi.org/10.3390/ma18163925 - 21 Aug 2025

Viewed by 806

Abstract

For reliable electronics, it is important to have an understanding of solder joint failure mechanisms. However, because of difficulties in real-time atomistic scale analysis during deformation, we still do not fully understand these mechanisms. Here, we report on the development of an innovative [...] Read more.

For reliable electronics, it is important to have an understanding of solder joint failure mechanisms. However, because of difficulties in real-time atomistic scale analysis during deformation, we still do not fully understand these mechanisms. Here, we report on the development of an innovative in situ method of observing the response of the microstructure to tensile strain at room temperature using high-voltage transmission electron microscopy (HV-TEM). This technique was used to observe events including dislocation formation and movement, grain boundary formation and separation, and crack initiation and propagation in a Sn-3 wt.%Ag-0.5 wt.%Cu (SAC305) alloy joint formed between copper substrates. Full article

(This article belongs to the Special Issue Phase Transformations in Metal Alloys)

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21 pages, 8401 KB

Open AccessArticle

Computational Study of Stress Distribution in Polyethylene Elements Due to Metal Components of Knee and Hip Implants Made from Different Metal Alloys

by Michał Sobociński and Marcin Nabrdalik

Materials 2025, 18(16), 3924; https://doi.org/10.3390/ma18163924 - 21 Aug 2025

Viewed by 399

Abstract

The complexity of the processes occurring in both natural and artificial joints necessitates carrying out the analysis on a 3D model based on already existing mathematical models. All the presented numerical calculations define qualitative conclusions about the influence of certain parameters of endoprostheses [...] Read more.

The complexity of the processes occurring in both natural and artificial joints necessitates carrying out the analysis on a 3D model based on already existing mathematical models. All the presented numerical calculations define qualitative conclusions about the influence of certain parameters of endoprostheses on the values of stresses and strains arising in polyethylene parts of hip and knee endoprostheses. The obtained results make it possible to reveal “weak points” in the studied models and thus counteract the later effects resulting from premature wear of the endoprosthesis components. The study included a numerical analysis of the stress and strain distribution of polyethylene components of hip and knee endoprostheses working with the most commonly used material associations in this type of solution. The most common are metal alloys and ceramics. The analyses were carried out using ADINA and Autodesk Simulation Mechanical software. Geometric models were designed based on current solutions used by leading endoprosthesis manufacturers. The load models adopted are based on models commonly used in musculoskeletal biomechanics. Particular attention was paid to modeling the resistance due to friction at the hip endoprosthesis node. To build the hip endoprosthesis model, eight-node 3D solid elements were used. Due to the axisymmetric geometry of the model, the resulting discrete model consisted of 10,000 cubic elements described by 10,292 nodes. In the case of the knee endoprosthesis, a finite element mesh was adopted for the calculations, which was built with 3600 3D solid cubic elements and 4312 nodes. The accuracy of the adopted numerical model did not differ from the generally used solutions in this field. Full article

(This article belongs to the Special Issue Polymers and Plastic Waste: Properties, Mechanics, Chemical and Thermal Recycling)

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18 pages, 6544 KB

Open AccessArticle

Corrosion and Mechanical Properties of Q500 qENH Steel in Simulated Plateau Environment

by Yanchen Liu, Xin Liu, Tao Lan, Zexu Li, Guangjie Xing and Shuailong Song

Materials 2025, 18(16), 3923; https://doi.org/10.3390/ma18163923 - 21 Aug 2025

Viewed by 385

Abstract

In high-altitude corrosive environments, weathering steel is widely applied due to its excellent corrosion resistance. However, the welded joint regions, where the chemical composition and microstructure undergo changes, are susceptible to the corrosion-induced degradation of mechanical properties. This study investigates the corrosion–mechanical synergistic [...] Read more.

In high-altitude corrosive environments, weathering steel is widely applied due to its excellent corrosion resistance. However, the welded joint regions, where the chemical composition and microstructure undergo changes, are susceptible to the corrosion-induced degradation of mechanical properties. This study investigates the corrosion–mechanical synergistic degradation behavior of a 16 mm thick Q500 qENH base metal and its V-type and Y-type welded joint specimens. Periodic immersion corrosion tests were conducted to simulate plateau atmospheric conditions, followed by mechanical performance evaluations. Corrosion metrics—including corrosion rate, cross-sectional loss, penetration depth, and corrosion progression speed—were analyzed in relation to mechanical indicators such as the fracture location, yield load, ultimate load, yield strength, and tensile strength at varying exposure durations. The results indicate that the corrosion process exhibits distinct layering, with a two-stage characteristic of rapid initial corrosion followed by slower progression. Welded joints consistently exhibit higher corrosion rates than the base metal, with the rate difference evolving nonlinearly in an “increase–decrease–stabilization” trend. After corrosion, the mechanical performance degradation of welded joint specimens is more severe than that of base metal specimens. Full article

(This article belongs to the Special Issue Advanced Steel Materials: 3D Printing, Phase Transformation, and Mechanical Properties)

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20 pages, 4778 KB

Open AccessArticle

Experimental Study on Bending Fatigue Performance of ADI Gears Under Different Applied Load Levels

by Lijun Wang, Hui Wei, Hsinshen Ho, Bo Hu, Yangyang Li and Dongfei Wang

Materials 2025, 18(16), 3922; https://doi.org/10.3390/ma18163922 - 21 Aug 2025

Viewed by 423

Abstract

As austempered ductile iron (ADI) is a key gear material for meeting the lightweight and cost-effective demands of new energy vehicles, its bending fatigue performance has a direct impact on vehicle transmission efficiency. In the present work, QTD 800 gears were subjected to [...] Read more.

As austempered ductile iron (ADI) is a key gear material for meeting the lightweight and cost-effective demands of new energy vehicles, its bending fatigue performance has a direct impact on vehicle transmission efficiency. In the present work, QTD 800 gears were subjected to bending fatigue testing using a combination of the conventional group method and the staircase method, with considerations given to fatigue life and fatigue limit at different reliability levels. Subsequently, the gears were characterized using optical microscopy and a microhardness tester to examine their metallographic structure and determine their hardness. The results indicate that the bending fatigue limits corresponding to gear reliability levels of 50%, 90%, and 99% are 390.00 MPa, 372.55 MPa, and 358.32 MPa, respectively. It was also observed that higher gear life stability corresponds to a lower sustainable fatigue limit stress. The analyses further reveal that under low loads, the main crack exhibits a relatively straight and smooth propagation trajectory, formed through the slow extension of an existing crack, whereas under high loads, the main crack displays a rough and serrated appearance, arising from the coalescence of microcracks initiated around graphite nodules. Full article

(This article belongs to the Section Metals and Alloys)

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13 pages, 5805 KB

Open AccessArticle

Study on the Effect of the Plunging Depth of Stirring Pin on the Performance of 6061-T6 Aluminum Alloy Refill Friction Stir Spot Welded Zone

by Di Jiang, Igor Kolupaev, Hongfeng Wang and Xiaole Ge

Materials 2025, 18(16), 3921; https://doi.org/10.3390/ma18163921 - 21 Aug 2025

Viewed by 397

Abstract

In this study, under varying PDSP (plunging depths of stirring pin) and process parameters, refill friction stir spot welding tests were performed on 6061-T6 aluminum alloy, relying on a stirring tool with a 12 mm sleeve diameter and an 8 mm stirring pin [...] Read more.

In this study, under varying PDSP (plunging depths of stirring pin) and process parameters, refill friction stir spot welding tests were performed on 6061-T6 aluminum alloy, relying on a stirring tool with a 12 mm sleeve diameter and an 8 mm stirring pin diameter. The results manifested the internal defects in the weld zone when PDSP was 0, notwithstanding the alterations in process parameters. However, these flaws disappeared when PDSP was 0.5 mm and 1 mm. In the weld zone, PDSP exerted a dramatic effect on the internal metal flow state, particularly the curvature of the “Hook” shape and the width of the bonding ligament. It changed the downward bending of the ‘Hook’ into an upward one, influencing the fracture behavior of the weld zone and elevating the ULSF (ultimate lap shear force) by up to 20% (PDSP = 0.5 mm, welding speed = 30 mm/min, rotation speed is 1200 rpm). Besides, the PDSP intensified the PAZ (pin affected zone) pressure, induced more metal flowing into the SAZ (sleeve affected zone), thus reinforced the SAZ-TMAZ(thermomechanically affected zone) bonding strength, and upgraded the region’s microhardness. In summary, the PDSP is commendable for bolstering the weld zone’s performance, but excessively large PDSP values incur drastic indentations in the PAZ, which diminish the ULSF. Full article

(This article belongs to the Special Issue Evaluation of Mechanical Properties and Microstructure of Lightweight Alloys)

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19 pages, 5526 KB

Open AccessArticle

Low Cycle Fatigue Life Prediction for Hydrogen-Charged HRB400 Steel Based on CPFEM

by Bin Zeng, Xue-Fei Wei, Ji-Zuan Tan and Ke-Shi Zhang

Materials 2025, 18(16), 3920; https://doi.org/10.3390/ma18163920 - 21 Aug 2025

Viewed by 448

Abstract

Addressing the limitations of traditional fatigue life prediction methods, which rely on extensive experimental data and incur high costs, and given the current absence of studies that employ deformation inhomogeneity parameters to construct fatigue-indicator parameter (FIP) for predicting low-cycle fatigue (LCF) life of [...] Read more.

Addressing the limitations of traditional fatigue life prediction methods, which rely on extensive experimental data and incur high costs, and given the current absence of studies that employ deformation inhomogeneity parameters to construct fatigue-indicator parameter (FIP) for predicting low-cycle fatigue (LCF) life of metals in hydrogen environments, this study firstly explores how hydrogen pre-charging influences the LCF behavior of hot-rolled ribbed bar grade 400 (HRB400) steel via experimental and crystal plasticity simulation, and focus on the relationship between the fatigue life and the evolution of microscale deformation inhomogeneity. The experimental results indicate that hydrogen charging causes alterations in cyclic hysteresis, an expansion of the elastic range of the stabilized hysteresis loop, and a significant reduction in LCF life. Secondly, a novel FIP was developed within the crystal plasticity finite element method (CPFEM) framework to predict the LCF life of HRB400 steel under hydrogen influence. This FIP incorporates three internal variables: hydrogen embrittlement index, axial strain variation coefficient, and macroscopic stress ratio. These variables collectively account for the hydrogen charging effects and stress peak impacts on the microscale deformation inhomogeneity. The LCF life of hydrogen-charged HRB400 steel can be predicted using this new FIP. We performed fatigue testing under only one loading condition to measure the corresponding fatigue life and determine the FIP critical value. This helped predict fatigue life under different cyclic loading conditions for the same hydrogen-charged material. We compared the experimental data to validate the novel FIP to accurately predict the LCF life of hydrogen-charged HRB400 steel. The error between the predicted results and the measured results is limited to a factor of two. Full article

(This article belongs to the Section Metals and Alloys)

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13 pages, 2420 KB

Open AccessArticle

Comparative Evaluation of Stress Distribution and Permeability Characteristics in Bentonite Cutoff Walls Using CPTU and ABAQUS Methods

by Xuepeng Li, Yufu Li, Chao Yan, Fengyun Wang and Xiaoyan Liu

Materials 2025, 18(16), 3919; https://doi.org/10.3390/ma18163919 - 21 Aug 2025

Viewed by 388

Abstract

Bentonite materials are extensively used in cutoff walls at landfill sites. This study calculates the stress and permeability characteristics of bentonite materials using the piezocone penetration test (CPTU) and ABAQUS simulations. The lateral effective stress of bentonite materials is evaluated using arching models, [...] Read more.

Bentonite materials are extensively used in cutoff walls at landfill sites. This study calculates the stress and permeability characteristics of bentonite materials using the piezocone penetration test (CPTU) and ABAQUS simulations. The lateral effective stress of bentonite materials is evaluated using arching models, lateral squeezing models, and a modified lateral squeezing model. Pore pressure dissipation types are categorized into standard and non-standard, with the coefficient of consolidation obtained using the half dissipation time of excess pore pressure (t₅₀) method. In the standard dissipation type, the excess pore pressure gradually dissipates over time after the cone stops penetrating. In contrast, the non-standard dissipation type is characterized by an initial increase in pore pressure until it reaches a maximum value, followed by a decrease to hydrostatic pressure. Additionally, the pore pressure dissipation process in bentonite cutoff walls is recorded and analyzed over various time intervals. Finally, the relationship between hydraulic conductivity and t₅₀ at landfill sites is established based on standard and non-standard dissipation types using CPTU and ABAQUS methods. The t₅₀ method is used for the standard dissipation type, while a modified t_50m method is used for the non-standard dissipation type from CPTU and a t_50m method is used in the non-standard dissipation type from CPTU. The t_50m is the modified value derived from t₅₀. Cutoff walls made from bentonite materials offer the advantage of enhancing the isolation effects and meeting the design requirement of permeability (1.0 × 10⁻⁷ cm/s). Full article

(This article belongs to the Special Issue Development and Engineering Application of Green and Low-Carbon Infrastructure Construction Materials)

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23 pages, 7851 KB

Open AccessArticle

Multilayer Graphene Nanoshells from Biomass for Fast-Charge, Long-Cycle-Life and Low-Temperature Li-Ion Anodes

by Kevin R. McKenzie, Jr., Nathan A. Banek and Michael J. Wagner

Materials 2025, 18(16), 3918; https://doi.org/10.3390/ma18163918 - 21 Aug 2025

Viewed by 434

Abstract

Graphene nanoshells (MGNS) were prepared from cellulose, a sustainable biopolymer. Different sizes/morphologies were obtained by simply changing the metal catalyst salt in the synthesis. The MGNS were shown to reversibly cycle Li-ions by an intercalation mechanism similar to graphite. The reversible capacity of [...] Read more.

Graphene nanoshells (MGNS) were prepared from cellulose, a sustainable biopolymer. Different sizes/morphologies were obtained by simply changing the metal catalyst salt in the synthesis. The MGNS were shown to reversibly cycle Li-ions by an intercalation mechanism similar to graphite. The reversible capacity of each MGNS prepared from different metal salts correlates well to its degree of 3-D graphitic order. The small size of the MGNS allows for short Li diffusion distances and very rapid charging, obtaining a 20% charge in 36 s (100 C rate). The unique spherical structure provides stable cycling, losing only 3.8% capacity over 900 cycles, and eliminates exfoliation that occurs when cycling graphite in propylene carbonate (PC), an inexpensive, environmentally friendly electrolyte. This enables cycling in a PC-only solvent-based electrolyte, with stable cycling and high capacities at temperatures as low as −35 °C. At this very low temperature, 95% of the RT reversible capacity is retained, with only a modest charge potential increase due to the increase in viscosity of the solvent. Full article

(This article belongs to the Special Issue Advances in Biomass-Based Materials and Their Applications (2nd Edition))

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31 pages, 8900 KB

Open AccessArticle

Attention-Fused Staged DWT-LSTM for Fault Diagnosis of Embedded Sensors in Asphalt Pavement

by Jiarui Zhang, Haihui Duan, Songtao Lv, Dongdong Ge and Chaoyue Rao

Materials 2025, 18(16), 3917; https://doi.org/10.3390/ma18163917 - 21 Aug 2025

Viewed by 379

Abstract

Fault diagnosis for embedded sensors in asphalt pavement faces significant challenges, including the scarcity of real-world fault data and the difficulty in identifying compound faults, which severely compromises the reliability of monitoring data. To address these issues, this study proposes an intelligent diagnostic [...] Read more.

Fault diagnosis for embedded sensors in asphalt pavement faces significant challenges, including the scarcity of real-world fault data and the difficulty in identifying compound faults, which severely compromises the reliability of monitoring data. To address these issues, this study proposes an intelligent diagnostic framework that integrates a Discrete Wavelet Transform (DWT) with a staged, attention-based Long Short-Term Memory (LSTM) network. First, various fault modes were systematically defined, including short-term (i.e., bias, gain, and detachment), long-term (i.e., drift), and their compound forms. A fine-grained fault injection and labeling strategy was then developed to generate a comprehensive dataset. Second, a novel diagnostic model was designed based on a “Decomposition-Focus-Fusion” architecture. In this architecture, the DWT is employed to extract multi-scale features, and independent sub-models—a Bidirectional LSTM (Bi-LSTM) and a stacked LSTM—are subsequently utilized to specialize in learning short-term and long-term fault characteristics, respectively. Finally, an attention network intelligently weights and fuses the outputs from these sub-models to achieve precise classification of eight distinct sensor operational states. Validated through rigorous 5-fold cross-validation, experimental results demonstrate that the proposed framework achieves a mean diagnostic accuracy of 98.89% (±0.0040) on the comprehensive test set, significantly outperforming baseline models such as SVM, KNN, and a unified LSTM. A comprehensive ablation study confirmed that each component of the “Decomposition-Focus-Fusion” architecture—DWT features, staged training, and the attention mechanism—makes an indispensable contribution to the model’s superior performance. The model successfully distinguishes between “drift” and “normal” states—which severely confuse the baseline models—and accurately identifies various complex compound faults. Furthermore, simulated online diagnostic tests confirmed the framework’s rapid response capability to dynamic faults and its computational efficiency, meeting the demands of real-time monitoring. This study offers a precise and robust solution for the fault diagnosis of embedded sensors in asphalt pavement. Full article

(This article belongs to the Special Issue Green and Sustainable Infrastructure Construction Materials (3rd Edition))

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16 pages, 2397 KB

Open AccessArticle

Electromagnetic Field Shielding Using Interior Paints Enhanced with Metal Powders

by Ján Zbojovský and Pavol Liptai

Materials 2025, 18(16), 3916; https://doi.org/10.3390/ma18163916 - 21 Aug 2025

Viewed by 431

Abstract

This article deals with the issue of electromagnetic radiation, specifically methods of eliminating radiation using protective coatings. Protective coatings were created from commercially available fabricated but also recycled metal powders and commonly available interior paint. The aim of the experiments was to produce [...] Read more.

This article deals with the issue of electromagnetic radiation, specifically methods of eliminating radiation using protective coatings. Protective coatings were created from commercially available fabricated but also recycled metal powders and commonly available interior paint. The aim of the experiments was to produce protective coatings with different qualitative and quantitative compositions and subsequently test their shielding effects. For the preparation of the coatings, mixtures in the form of commercially produced powder with a particle size of <10 μm were used, namely aluminum oxide (Al₂O₃), manganese dioxide (MnO₂), and graphite (C). Recycled powders are powdered iron (Fe) and zinc oxide (ZnO) with a particle size of <50 μm. The powders were mixed in various ratios and compounds into a commercially available white interior paint. Measurements were performed in the frequency range of 0.9–9 GHz with a step of 0.1 GHz, evaluating the shielding effectiveness, absorption, and reflection. The best shielding values were achieved for samples containing 100 g of carbon powder, 100 g of iron powder, and 100 g of manganese dioxide, ranging from 0.38 to 6.2 dB in the full measured frequency range. Full article

(This article belongs to the Special Issue Development and Modification of New or Recycled Materials and Technological Processes Toward Sustainable Development (Second Edition))

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20 pages, 6679 KB

Open AccessArticle

The Influence of Heat Treatment on the Mechanical Properties of AlMn1Cu Aluminium Alloy with One-Sided AlSi7.5 Cladding Used in Heat Exchangers

by Martyna Zemlik, Beata Białobrzeska and Daniel Tokłowicz

Materials 2025, 18(16), 3915; https://doi.org/10.3390/ma18163915 - 21 Aug 2025

Viewed by 407

Abstract

The aim of this study was to determine the influence of heat treatment parameters on the microstructure and mechanical properties of the AlMn1Cu (EN AW-3003) aluminium alloy with a one-sided cladding layer of AlSi7.5 alloy (EN AW-4343). The investigation was conducted within an [...] Read more.

The aim of this study was to determine the influence of heat treatment parameters on the microstructure and mechanical properties of the AlMn1Cu (EN AW-3003) aluminium alloy with a one-sided cladding layer of AlSi7.5 alloy (EN AW-4343). The investigation was conducted within an annealing temperature range of 200 °C to 500 °C, analysing changes in hardness, mechanical strength, formability, and planar anisotropy. The results clearly indicate that within the temperature range of 300–340 °C, an intensive process of static recrystallisation occurs, leading to the restoration of a fine-grained and homogeneous microstructure. This is accompanied by a sharp reduction in hardness and yield strength, along with a significant increase in ductility and deep drawing capability. A notable reduction in the anisotropy of plastic properties was also observed, confirming effective homogenisation of the material’s microstructure. The findings unambiguously demonstrate that heat treatment within the range of 300–500 °C enables the formation of an isotropic microstructure with low hardness and high formability, rendering the material particularly suitable for shaping thin-walled components, including heat exchangers. Full article

(This article belongs to the Special Issue Alloys and Composites: Structural and Functional Applications, Third Edition)

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22 pages, 4188 KB

Open AccessArticle

Composite Materials Based on Biochar Obtained from Tomato Wastes and Fe₃O₄/MnO₂ Used for Paracetamol Adsorption

by Adina Stegarescu, Ildiko Lung, Alin Cârdan, Mariana Bocșa, Alexandru Turza, Mihaela Diana Lazar, Monica Dan, Septimiu Tripon, Irina Kacso, Stelian Pintea, Ocsana Opriș and Maria-Loredana Soran

Materials 2025, 18(16), 3914; https://doi.org/10.3390/ma18163914 - 21 Aug 2025

Viewed by 534

Abstract

The pharmaceutical contamination of water, especially by widely used drugs, presents important environmental and health concerns due to the inefficiency of conventional treatment methods. The present study proposes a sustainable solution using biochar (Bch) obtained from tomato waste, functionalized with Fe₃O [...] Read more.

The pharmaceutical contamination of water, especially by widely used drugs, presents important environmental and health concerns due to the inefficiency of conventional treatment methods. The present study proposes a sustainable solution using biochar (Bch) obtained from tomato waste, functionalized with Fe₃O₄ and MnO₂ nanoparticles, for the removal of paracetamol from aqueous solutions. The composite materials were synthesized, characterized, and evaluated under varying conditions, including pH, temperature, contact time, initial drug concentration, and adsorbent dose. The materials exhibited porous structures with wide pore size distributions. Optimal removal efficiency was achieved for 30 mg L⁻¹ paracetamol concentration, pH 2, 25 °C, 0.3 g L⁻¹ adsorbent dose, and 20 min contact time. The Freundlich isotherm provided the best fit for the adsorption data. Kinetic studies revealed that the pseudo-second-order model best described the adsorption process. Thermodynamic parameters indicated that the process was spontaneous, feasible, and exothermic. Compared with similar materials derived from agricultural waste, the tomato waste-based composites demonstrated competitive adsorption capacities. These findings suggest that Bch-HCl/MnO₂ and Bch-HCl/Fe₃O₄/MnO₂ are promising, cost-effective adsorbents for mitigating pharmaceutical pollutants in wastewater. Full article

(This article belongs to the Special Issue Functional Nanocomposites: Preparation, Characterization and Applications)

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15 pages, 2939 KB

Open AccessArticle

Optimizing Gun Drilling Parameters for Oxygen-Free Copper Using Response Surface Methodology and Genetic Algorithm

by Xiaolan Han, Hailong Wang, Yazhou Feng and Shengdun Zhao

Materials 2025, 18(16), 3913; https://doi.org/10.3390/ma18163913 - 21 Aug 2025

Viewed by 391

Abstract

To improve chip removal efficiency and drilling performance in oxygen-free copper, a multi-objective optimization of gun drilling process parameters was conducted using a response surface methodology and a genetic algorithm. The Box–Behnken Design (BBD) response surface analysis method was employed to evaluate the [...] Read more.

To improve chip removal efficiency and drilling performance in oxygen-free copper, a multi-objective optimization of gun drilling process parameters was conducted using a response surface methodology and a genetic algorithm. The Box–Behnken Design (BBD) response surface analysis method was employed to evaluate the effects of feed rate, cutting speed, and cutting fluid pressure on the chip evacuation coefficient and chip volume ratio. Experimental results indicate that among the three factors, the feed rate has the most significant influence, followed by the cutting speed and the cutting fluid pressure. Additionally, the interaction between the cutting speed and the cutting fluid pressure notably impacts both chip evacuation and chip volume ratio. Using response surface modeling, a three-dimensional predictive model was developed. Based on this fitted model, optimal gun drilling parameters were identified through genetic algorithm optimization, minimizing the chip evacuation coefficient and chip volume ratio to achieve an optimized machining configuration. The optimal drilling parameters were identified as a feed rate of 0.019 mm/r, a spindle speed of 47.1 m/min, and a cutting fluid pressure of 2.4 MPa. Under these conditions, a chip evacuation coefficient of 3.2951 and a chip volume ratio of 3.3345 were achieved. The resulting chips predominantly exhibited a C-shaped morphology, accompanied by smooth and efficient evacuation. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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16 pages, 8918 KB

Open AccessArticle

The Influence of Cyclic Torsion with Application of Current Pulses on the Formability of CuZn30 Brass

by Zbigniew Zimniak, Wojciech Weiler and Karol Jaśkiewicz

Materials 2025, 18(16), 3912; https://doi.org/10.3390/ma18163912 - 21 Aug 2025

Viewed by 417

Abstract

This article presents a study on symmetric cyclic torsion with the application of electric pulses and their effect on the formability of α-brass CuZn30 at room temperature. Preliminary tests were carried out using a conventional monotonic torsion test. The obtained results served as [...] Read more.

This article presents a study on symmetric cyclic torsion with the application of electric pulses and their effect on the formability of α-brass CuZn30 at room temperature. Preliminary tests were carried out using a conventional monotonic torsion test. The obtained results served as a reference for the subsequently conducted symmetric cyclic torsion tests. Then, under analogical deformation conditions, tests were conducted with the application of electric pulses featuring various parameters: different pulse durations and different periods, i.e., intervals between successive pulses. Microstructural studies of the deformed material were conducted, including examinations using a microscope equipped with an electron backscatter diffraction (EBSD) detector. Based on the results, it was found that the application of electric pulses during cyclic torsion tests consistently leads to a reduction in stress compared to cyclic torsion tests conducted at ambient temperature without current flow. In most cases, it also results in an increase in strain compared to tests without the application of electric pulses. The electroplastometric torsion tests carried out in this study within the bulk forming process are the first of their kind to combine cyclic torsion with electrically assisted forming (EAF). The proposed combination may lead to the development of new deformation methods in real manufacturing processes. Full article

(This article belongs to the Section Mechanics of Materials)

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22 pages, 9293 KB

Open AccessArticle

Synthesis, Characterization, and In Vitro Cytotoxic Evaluation of Neodymium-Doped Cobalt Ferrite Nanoparticles on Human Cancer Cell Lines

by Slaviţa Rotunjanu, Armand Gogulescu, Narcisa Laura Marangoci, Andrei-Ioan Dascălu, Marius Mioc, Roxana Racoviceanu, Alexandra Mioc, Tamara Maksimović, Oana Eșanu, Gabriela Antal and Codruţa Șoica

Materials 2025, 18(16), 3911; https://doi.org/10.3390/ma18163911 - 21 Aug 2025

Viewed by 428

Abstract

Cancer is still the world’s most prevalent cause of death, and the limited efficacy of current treatments highlights the requirement for new therapeutic approaches. In this study, neodymium (Nd)-doped cobalt ferrite (CoFe_2₋zNd_zO₄, z = 0; 0.01; 0.02; [...] Read more.

Cancer is still the world’s most prevalent cause of death, and the limited efficacy of current treatments highlights the requirement for new therapeutic approaches. In this study, neodymium (Nd)-doped cobalt ferrite (CoFe_2₋zNd_zO₄, z = 0; 0.01; 0.02; 0.03; 0.05; 0.1) nanoparticles (Nd0-Nd5) were synthesized via the combustion method. The structural, morphological, and magnetic properties were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometry (VSM), and scanning transmission electron microscopy (STEM) analysis. The synthesized compounds demonstrated single-phase spinel structures, with morphological differences observed between undoped and Nd-doped samples. The biological activity of the nanoparticles was evaluated on immortalized human keratinocytes (HaCaT) and on cancer cell lines: melanoma (A375), breast adenocarcinoma (MCF-7), and pancreatic carcinoma (PANC-1). The cytotoxic effects of Nd0-Nd5 (50–1000 μg∙mL⁻¹) were assessed through Alamar Blue and lactate dehydrogenase (LDH) release assays. The results indicated a dose-dependent cytotoxic effect in cancer cell lines. Changes in cell morphology, suggesting the induction of the apoptotic processes, were observed through immunofluorescence staining of F-actin and nuclei. These findings highlight the potential of Nd-doped cobalt ferrite nanoparticles as selective anticancer agents, warranting further investigation to fully elucidate their mechanisms of action and therapeutic applicability. Full article

(This article belongs to the Special Issue New Functional Materials for Biomedical Applications)

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18 pages, 6936 KB

Open AccessArticle

Anisotropic Behavior in Microstructures and Properties of Refractory Tungsten Metal Produced by Laser Powder Bed Fusion

by Jinguo Ge, Heming Wu, Hongsen Liu, Yanan Zhu, Yan Chen, Wangwei Zhan, Liang Zhang and Zhuming Liu

Materials 2025, 18(16), 3910; https://doi.org/10.3390/ma18163910 - 21 Aug 2025

Viewed by 438

Abstract

This work employed laser powder bed fusion (LPBF) technology to prepare pure tungsten (W) metal components and investigated their internal defects, microstructural characteristics and mechanical properties within the horizontal and vertical planes to evaluate their anisotropic behavior. The steep temperature gradient and extremely [...] Read more.

This work employed laser powder bed fusion (LPBF) technology to prepare pure tungsten (W) metal components and investigated their internal defects, microstructural characteristics and mechanical properties within the horizontal and vertical planes to evaluate their anisotropic behavior. The steep temperature gradient and extremely rapid cooling rate during the LPBF process caused the as-deposited W grains to grow in a columnar crystal structure along the vertical height direction, with cracks propagating along the high-angle grain boundaries (HAGBs). Although the near-equiaxed W grains within the horizontal plane were finer than the epitaxial grains within the vertical plane, the increased number of cracks within the horizontal plane weakened the fine-grained strengthening effect, resulting in lower hardness and wear resistance within the horizontal plane than within the vertical plane. The wear behavior transformed from a comprehensive wear mechanism involving delamination wear and abrasive wear within the vertical plane to an abrasive wear mechanism with slight adhesive wear within the horizontal plane. The reported results demonstrate that the anisotropic behavior of hardness and wear resistance within the different deposition planes was mainly attributed to the differences in microstructure and crack distribution between the horizontal and vertical planes of LPBF-fabricated W parts. Full article

(This article belongs to the Special Issue Advances in 3D Printing Technologies: Design, Manufacturing, and Applications)

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19 pages, 3819 KB

Open AccessArticle

ZnO/SiO₂ Filler-Incorporated Resin Composites for Vat Photopolymerization of Dental Restorations with Antimicrobial Efficacy

by Jong-Won Jeon, Gyu-Nam Kim, Jae-Min Jung and Young-Hag Koh

Materials 2025, 18(16), 3909; https://doi.org/10.3390/ma18163909 - 21 Aug 2025

Viewed by 627

Abstract

This study aimed to develop dental resin composites containing ZnO/SiO₂ ceramic particles as an antimicrobial filler for producing provisional dental restorations using the lithography-based liquid crystal display (LCD) 3D printing technique. Three types of dental resin-ceramic composites with different filler contents (0 [...] Read more.

This study aimed to develop dental resin composites containing ZnO/SiO₂ ceramic particles as an antimicrobial filler for producing provisional dental restorations using the lithography-based liquid crystal display (LCD) 3D printing technique. Three types of dental resin-ceramic composites with different filler contents (0 wt%, 5 wt%, and 10 wt%) were prepared to offer high antimicrobial efficacy. Printing parameters, particularly off-time, were optimized for each composition to achieve high-quality prints. Mechanical testing demonstrated increased hardness and elastic modulus. In addition, the 10 vol% composite exhibited a three-point flexural strength of 113.4 MPa, exceeding the 100 MPa requirement specified in ISO 4049:2019 for provisional dental materials. Antimicrobial testing showed a significant reduction in Streptococcus mutans colonies, with up to 84.4% decrease for the 10 vol% composite compared to the unfilled resin. A provisional 3-unit bridge was successfully printed using the 10 vol% composite, demonstrating practical applicability. Full article

(This article belongs to the Special Issue Dental Biomaterials: Synthesis, Characterization, and Applications)

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12 pages, 3356 KB

Open AccessArticle

Molecular Dynamics Simulation Study on the Cooling Behavior and Mechanical Properties of Silicone Carbide/Aluminum Composites

by Guanzhuo Zhou, Shiming Hao, Jingpei Xie, Hai Huang, Guopeng Zhang, Bin Cai, Yunjia Shi, Jing Wang and Jiefang Wang

Materials 2025, 18(16), 3908; https://doi.org/10.3390/ma18163908 - 21 Aug 2025

Viewed by 403

Abstract

The mismatch of the coefficient of thermal expansion (CTE) between the reinforcement and the matrix leads to thermal residual stresses and defects upon cooling from the processing temperature to room temperature. The residual stresses and defects have a significant impact on the mechanical [...] Read more.

The mismatch of the coefficient of thermal expansion (CTE) between the reinforcement and the matrix leads to thermal residual stresses and defects upon cooling from the processing temperature to room temperature. The residual stresses and defects have a significant impact on the mechanical properties of metal-matrix composites. To investigate the effect of cooling temperature on the residual stresses’ distribution and mechanical properties of SiC/Al, we investigated the cooling process of SiC/Al from different initial temperatures to room temperature. We found that residual stresses mainly distributed in the interface of SiC/Al composites after cooling, and the higher the initial temperature of cooling, the higher the value of residual stresses and the greater the degree of atomic displacement. During the cooling process, the Shockley partials and stair-rod dislocations were the two dominant dislocation structures. After cooling, the length of Shockley partials was about 80% and the length of stair-rod dislocations was about 18%. The mechanical properties of SiC/Al composites reduced after cooling. These results have filled the gap in understanding the mechanism of defect evolution in SiC/Al composites under cooling conditions, as well as the influence of cooling conditions on the mechanical properties of the material. Full article

(This article belongs to the Section Mechanics of Materials)

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12 pages, 13126 KB

Open AccessArticle

Wear Characteristics of WC-Co Cutting Tools Obtained by the U-FAST Method During Particleboard Milling

by Joanna Wachowicz, Zbigniew Bałaga and Piotr Podziewski

Materials 2025, 18(16), 3907; https://doi.org/10.3390/ma18163907 - 21 Aug 2025

Viewed by 383

Abstract

This article presents the wear characteristics of the working surface of WC-Co (Tungsten Carbide–Cobalt) tungsten carbide tools obtained using the innovative U-FAST (Upgraded Field-Assisted Sintering Technology) method for particleboard machining. Three groups of tools with a similar chemical composition but differing WC (Tungsten [...] Read more.

This article presents the wear characteristics of the working surface of WC-Co (Tungsten Carbide–Cobalt) tungsten carbide tools obtained using the innovative U-FAST (Upgraded Field-Assisted Sintering Technology) method for particleboard machining. Three groups of tools with a similar chemical composition but differing WC (Tungsten Carbide) grain sizes were tested. Milling tests were carried out on a CNC (Computer Numerical Control) machine tool with the following cutting parameters: spindle rotation at 15,000 rpm, a feed rate of 0.25 mm per tooth, and a feed rate of 3.75. The experimental results show that tools with submicron WC grit sizes of 0.4 µm and 0.8 µm have the longest tool life. Wear of the cutting edges occurred through the removal of the cobalt bond between the tungsten carbide grains, leading to fracture and mechanical removal of the grains from the cutting edge surface. The similarities in the relative wear characteristics of blades with submicron tungsten carbide grain sizes suggest that micro-abrasion and bond phase extrusion may be the main wear mechanisms under the experimental conditions. Nanometric WC grain size significantly influences tool wear through chipping and cracking. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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10 pages, 2877 KB

Open AccessCommunication

Localized Surface Phonon Polaritons and Infrared Optical Absorption of ScAlN Nanoresonators

by Huanhuan Zhao, Tao Cheng, Xinlei Duan, Mingxin Lv, Jia-Yue Yang and Linhua Liu

Materials 2025, 18(16), 3906; https://doi.org/10.3390/ma18163906 - 21 Aug 2025

Viewed by 416

Abstract

Alloying AlN with ScN provides a robust strategy for engineering its intrinsic bandgap, phonons and dielectric functions, and ScAlN alloys have demonstrated great promise in applications including the 5G mobile network, surface acoustic wave devices and nanophotonics. Sc doping has been shown to [...] Read more.

Alloying AlN with ScN provides a robust strategy for engineering its intrinsic bandgap, phonons and dielectric functions, and ScAlN alloys have demonstrated great promise in applications including the 5G mobile network, surface acoustic wave devices and nanophotonics. Sc doping has been shown to greatly influence the phonons and infrared dielectric functions of AlN, yet few studies have focused on its influence on surface phonon polaritons, which are crucial to modulating the radiative properties of ScAlN metasurfaces. Herein, we combined first-principles and finite element method (FEM) simulations to fully investigate the effects of Sc incorporation on the phonon dispersion relation, propagation and localization of SPhPs and the modulated radiative properties of ScAlN nanoresonators. As the Sc doping concentration increases, the highest optical phonon frequencies are reduced and are largely directly related to enlarged lattice parameters. Consequently, the coupling strength among incident photons and phonons decreases, which leads to a reduced absorption peak in the infrared dielectric functions. Moreover, the propagation length of the SPhPs in ScAlN is largely reduced, and localized resonance modes gradually disappear at a higher Sc doping concentration. This work provides physical insights into the spectra tuning mechanisms of ScAlN nanoresonators via Sc doping and facilitates their applications in nanophotonic devices. Full article

(This article belongs to the Special Issue Research Progress of Advanced Crystals: Growth and Doping)

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15 pages, 3954 KB

Open AccessArticle

Molecular Dynamics Simulation on Orientation-Dependent Mechanical Behaviors of ZnO Single Crystals Under Nanoindentation

by Xiaolin Zhu, Jijun Li, Shiting Yang, Weiguang Zhang, Xiuxia Li, Hui Tang, Fengchao Lang, Lin Lin, Xiaohu Hou, Xueping Zhao and Jiayi Chen

Materials 2025, 18(16), 3905; https://doi.org/10.3390/ma18163905 - 21 Aug 2025

Viewed by 342

Abstract

The present study aims to investigate the orientation-dependent mechanical behaviors of ZnO single crystals under nanoindentation by molecular dynamics simulation. The load–indentation depth curves, atomic displacement, shear strain and dislocations for the c-plane, m-plane and a-plane ZnO single crystals were analyzed in detail. [...] Read more.

The present study aims to investigate the orientation-dependent mechanical behaviors of ZnO single crystals under nanoindentation by molecular dynamics simulation. The load–indentation depth curves, atomic displacement, shear strain and dislocations for the c-plane, m-plane and a-plane ZnO single crystals were analyzed in detail. The simulation results showed that the elastic deformation stage of the loading curves for the three oriented ZnO single crystals can be described well by the Herz elastic contact model. The Young modulus values for the c-plane, m-plane and a-plane ZnO were calculated to be 122.5 GPa, 158.3 GPa and 170.5 GPa, respectively. The onset of plastic deformation occurred first in a-plane ZnO, then in m-plane ZnO, and lastly in c-planeZnO. The atomic displacement vectors in the three oriented ZnO single crystals were in good agreement with the primary activated slip systems predicted by the maximum Schmid factor. For the c-plane ZnO, the activated pyramidal {

11 \bar{2} 2

}<

11 \bar{2} 3

> slip system led to a complex dislocation pattern surrounding the indenter. A U-shaped prismatic half-loop was formed in the [

2 \bar{11} 0

] direction, confirming the activation of the prismatic {

10 \bar{1} 0

}<

11 \bar{2} 0

> slip system. For the m-plane ZnO, the activated prismatic {

10 \bar{1} 0

}<

11 \bar{2} 0

> slip system led to the preferential nucleation of dislocations along the

[\bar{11} 20]

and [

\bar{2} 110

] directions. A prismatic loop was formed and emitted along the [

\bar{2} 110

] direction, governed by a confined glide on {

10 \bar{1} 0

} planes. For the a-plane ZnO, the activated prismatic {

10 \bar{1} 0

}<

11 \bar{2} 0

> slip system led to dislocations concentrated in the [

\bar{1} \bar{1} 20

] direction beneath the indentation pit, emitting a prismatic loop along this direction. Perfect dislocation (with a Burgers vector of 1/3 <

1 \bar{2} 10

>) is the dominant dislocation in the three oriented ZnO single crystals. The findings are expected to deepen insights into the anisotropic mechanical properties of ZnO single crystals, offering guidance for the development and applications of ZnO-based devices. Full article

(This article belongs to the Special Issue Corrosion Behavior and Mechanical Properties of Metallic Materials (Second Edition))

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21 pages, 3523 KB

Open AccessArticle

A Study on the Negative Friction Mechanisms in Piles Within Recycled Dredged Waste Fills

by Xiangyang Hou, Wei Sun, Yongle Chen, Xiaoli Yi, Yaohui Liu and Lulu Liu

Materials 2025, 18(16), 3904; https://doi.org/10.3390/ma18163904 - 21 Aug 2025

Viewed by 482

Abstract

Green and low-carbon filling materials, primarily composed of dredged waste fills, are commonly used in the foundation of coastal highways. These materials possess high water content and under-consolidation characteristics, which can lead to differential settlement between piles and the surrounding environment. However, mechanical [...] Read more.

Green and low-carbon filling materials, primarily composed of dredged waste fills, are commonly used in the foundation of coastal highways. These materials possess high water content and under-consolidation characteristics, which can lead to differential settlement between piles and the surrounding environment. However, mechanical models of negative friction in piles within recycled dredged waste fills are insufficiently developed and presented. A mechanical model for the negative friction of a single pile in a composite foundation, consisting of dredged waste fills and other materials, is established based on the load transfer method. Through centrifugal model testing and numerical simulations, the development of negative friction and the migration pattern of the neutral point are analyzed and clarified. The results show that the theoretical model based on improved transfer function can effectively predict the neutral point position and negative friction value (average relative error < 6.5%). The theoretical analysis and experimental results indicate that the downward load due to negative friction increases nonlinearly. The loading strength exhibits a clear relationship with the consolidation process. Additionally, the dynamic evolution of the neutral point position is strongly correlated with consolidation of dredged fills. The size of pile foundation significantly influences the distribution of negative friction. Results show that the increment in negative friction for a pile with a 1.05 m diameter is 7.3% higher than that for a pile with a 1.5 m diameter. Smaller-diameter piles are more susceptible to negative friction due to the higher friction strength per unit area. The negative frictional resistance will enter a stable period after 50 months of settlement. The investigation can provide significant references for the design of pile foundations in areas with reclaimed materials, improving the stability and safety of pile foundations in practical engineering. Full article

(This article belongs to the Section Construction and Building Materials)

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26 pages, 3225 KB

Open AccessReview

A Review on Comfort of Pedestrian Bridges Under Human-Induced Vibrations and Tuned Mass Damper Control Technologies

by Shoukun Zhang, Baijin Wu, Yong Tang, Han Zhang, Zheng Xu, Guoqiang Li and Shuang Lu

Materials 2025, 18(16), 3903; https://doi.org/10.3390/ma18163903 - 21 Aug 2025

Viewed by 468

Abstract

With the development of urban infrastructure construction, while pedestrian bridges meet traffic functions the issue of their comfort has become a core consideration in structural design. This is because the long-span lightweight structures, with their large flexibility and low fundamental frequencies, are also [...] Read more.

With the development of urban infrastructure construction, while pedestrian bridges meet traffic functions the issue of their comfort has become a core consideration in structural design. This is because the long-span lightweight structures, with their large flexibility and low fundamental frequencies, are also vulnerable to human-induced vibrations. Pedestrian load modellings include the deterministic time-domain model, which is widely adopted in codes due to its simplicity, the random model that takes into account individual variability, and the frequency-domain model. The deterministic time-domain model has abundant parameter determination results and has become relatively mature, while the latter two, although more rigorous, have relatively lagging development. Numerous studies have shown that acceleration limits are the main indicators for comfort assessment. Vertical vibrations are controlled by amplitude constraints, while for the lateral vibrations the “lateral lock-in” that can cause dynamic instability needs to be evaluated with particular emphasis. When comfort exceeds an acceptable degree, a prevalent countermeasure is to attach a Tuned Mass Damper (TMD) or Multiple Tuned Mass Damper (MTMD) system to the structure—the latter demonstrates stronger robustness when dealing with random pedestrian loads. Full article

(This article belongs to the Special Issue Carbon Capture, Utilization and Storage Technologies of Cement-Based Materials)

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24 pages, 5043 KB

Open AccessFeature PaperArticle

Design of Technological Parameters for Vibrocompression of Gypsum Concrete

by Leonid Dvorkin, Vadim Zhitkovsky and Yuri Ribakov

Materials 2025, 18(16), 3902; https://doi.org/10.3390/ma18163902 - 20 Aug 2025

Viewed by 534

Abstract

This paper deals with a method for producing gypsum concrete by vibropressing ultra-stiff concrete mixtures with a water–gypsum ratio (W/G) of 0.25–0.35 (stiffness 50–55 s according to Vebe), as well as the method of designing the composition of such concrete. The research was [...] Read more.

This paper deals with a method for producing gypsum concrete by vibropressing ultra-stiff concrete mixtures with a water–gypsum ratio (W/G) of 0.25–0.35 (stiffness 50–55 s according to Vebe), as well as the method of designing the composition of such concrete. The research was carried out using mathematical experimental design. Experimental and statistical polynomial models of strength and average density dependences on technological factors such as moisture content in the gypsum concrete mixture, aggregate consumption, and vibropressing parameters (dynamic punch pressure during vibration and process duration) were obtained. Models of the aggregate quantity and granulometric composition influence on the gypsum concrete strength at constant compaction parameters and changes in the mixture moisture content were obtained. Based on the obtained models, a method for designing the composition of vibropressed gypsum concrete on dense aggregate was developed. According to the proposed method, the aggregate-to-gypsum ratio (A/G) is first found, taking into account the given strength and quality of the materials. Next, the optimal W/G ratio, which ensures maximum compaction, is calculated and, after that, the residual air volume and the component consumption are obtained. The method allows determining the composition of gypsum concrete on dense aggregate, compacted by vibropressing of superhard mixtures according to a given compressive strength after 1 day of hardening in the range from 15 to 44 MPa. It also allows you to take into account the operating parameters of the molding plant, the aggregate grain composition, and determine the optimal moisture content of the gypsum concrete mixture. Full article

(This article belongs to the Special Issue Recycling and the Development of New Building Materials and Products—Third Edition)

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16 pages, 4468 KB

Open AccessArticle

Enhancing Fatigue Lifetime of Secondary AlZn10Si8Mg Alloys Through Shot Peening: Influence of Iron Content and Surface Defects

by Denisa Straková, Zuzana Šurdová, Eva Tillová, Lenka Kuchariková, Martin Mikolajčík, Denisa Závodská and Mario Guagliano

Materials 2025, 18(16), 3901; https://doi.org/10.3390/ma18163901 - 20 Aug 2025

Viewed by 389

Abstract

The rising demand for aluminium and environmental concerns highlight the need for a circular economy using recycled alloys. This study examines the effect of shot peening on the high-cycle fatigue life of secondary AlZn10Si8Mg alloys with different iron contents: Alloy A (0.14 wt.% [...] Read more.

The rising demand for aluminium and environmental concerns highlight the need for a circular economy using recycled alloys. This study examines the effect of shot peening on the high-cycle fatigue life of secondary AlZn10Si8Mg alloys with different iron contents: Alloy A (0.14 wt.% Fe) and Alloy B (0.56 wt.% Fe). Although both alloys showed similar tensile properties, Alloy B had higher porosity and finer β-Al₅FeSi intermetallics. Shot peening was applied at 100% and 1000% coverage to evaluate changes in surface roughness, porosity, residual stresses, and fatigue performance. The treatment significantly reduced surface-connected porosity via plastic deformation, enhancing fatigue life despite increased roughness. Fatigue tests showed a 21% increase in fatigue limit for Alloy A and a 6% gain for Alloy B at higher coverage. Fractographic analysis revealed that 95% of fatigue cracks initiated at surface pores. Residual stress measurements confirmed compressive stresses were limited to the near-surface layer, with minimal influence on subsurface crack propagation. Overall, shot peening proves to be an effective method for improving fatigue resistance in recycled aluminium alloys, even in alloys with elevated iron content, reinforcing their potential for structural applications under cyclic loading. Full article

(This article belongs to the Special Issue Fatigue, Damage and Fracture of Alloys)

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11 pages, 1720 KB

Open AccessArticle

Chemical Ordering in Liquid and Supercooled Ge₂Sb₂Te₅ Phase-Change Materials

by Tae Hoon Lee

Materials 2025, 18(16), 3900; https://doi.org/10.3390/ma18163900 - 20 Aug 2025

Viewed by 376

Abstract

The origin of chemical ordering in liquid and supercooled liquid Ge₂Sb₂Te₅ (GST) was investigated using ab initio molecular dynamics (AIMD) simulations. Bond dynamics were analyzed via continuous (

τ_{con}

) and intermittent (

τ_{i n t}

[...] Read more.

The origin of chemical ordering in liquid and supercooled liquid Ge₂Sb₂Te₅ (GST) was investigated using ab initio molecular dynamics (AIMD) simulations. Bond dynamics were analyzed via continuous (

τ_{con}

) and intermittent (

τ_{i n t}

) lifetimes. The intermittent lifetime (

τ_{i n t}

) reveals that chemically ordered Ge-Te and Sb-Te bonds are the most stable, although

τ_{con}

exhibits a stability anomaly. The faster increase of

τ_{i n t}

for these bonds upon cooling explains the overall chemical ordering. A novel ordering mechanism was identified through the analysis of bond separation dynamics. Te-Te ‘wrong’ bonds exhibit a unique dynamic instability, breaking and separating much faster than any other bond type, which actively drives the system towards chemical order. A correlation between lifetime and bond strength, as calculated by the Integrated Crystal Orbital Hamilton Population (ICOHP), supports these dynamic findings. Chemical ordering shows a positive correlation with medium-range structural order, evidenced by the instability of 4-fold rings containing wrong bonds. This study provides a detailed dynamic origin for ordering in liquid GST, highlighting the role of Te-Te bond relaxation. Full article

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17 pages, 6566 KB

Open AccessArticle

Microstructural and Mechanical Property Variations in 316L Stainless Steel Fabricated by Laser Powder Bed Fusion Under High-Density Processing Conditions

by Shun Zhang, Xudong Wu, Zhong Wang, Meiling Jiang, Guoliang Huang, Xiaoqiang Peng, Chen Yang, Junyan Zhu and Ke Huang

Materials 2025, 18(16), 3899; https://doi.org/10.3390/ma18163899 - 20 Aug 2025

Viewed by 499

Abstract

It has become a trend to precisely control the additive manufacturing process parameters within the high-density process window to obtain high-performance metal parts. However, there are few reports on this topic currently, leaving this research without sufficient references. This study took 316L austenitic [...] Read more.

It has become a trend to precisely control the additive manufacturing process parameters within the high-density process window to obtain high-performance metal parts. However, there are few reports on this topic currently, leaving this research without sufficient references. This study took 316L austenitic stainless steel as a case study. In total, 36 groups of specimens were manufactured by Laser powder bed melting (LPBF), and then, two highly dense specimens were selected to study the variation in their microstructure and properties. The densities of the selected specimens, S1 (VED = 81 J/mm³) and S2 (VED = 156.3 J/mm³), are 99.68% and 99.99%, respectively. The results indicated that, compared with the S1 specimen, the S2 specimen significantly decreased in terms of yield strength (YS), ultimate tensile strength (UTS), and elongation (EL), which are 7.28%, 6.34%, and 19.15%, respectively. The differences in mechanical properties were primarily attributed to differences in their microstructures. Further, compared with the S1 specimen, the fitted ellipse aspect ratio and average grain size of the S2 specimen increased by 79.88% and 53.45%, respectively, and the kernel average misorientation (KAM) value and geometric necessary dislocation (GND) density increased by 36.00% and 58.43%, respectively. Furthermore, the S1 specimen exhibited a strong texture in the <101>//Z direction, whereas no obvious texture was observed in the S2 specimen. Obviously, the reason why precise regulation within the dense parameter range can achieve better performance is that the microstructure and mechanical properties of the specimens prepared within the dense range are different. More importantly, this study provides a feasible framework for optimizing alloys with broad and dense parameter ranges, demonstrating the potential to achieve high-performance components through precise parameter control. Furthermore, the results reveal that even within a wide range of high-density forming parameters, significant variations in microstructure and mechanical properties can arise depending on the selected parameter combinations. These findings underscore the critical importance of meticulous process parameter optimization and microstructural regulation in tailoring material properties. Full article

(This article belongs to the Special Issue New Advances in High-Temperature Structural Materials)

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14 pages, 4377 KB

Open AccessArticle

Compressive Mechanical Properties of Lattice Structures with Varied Structural Parameters Prepared by Stereolithography

by Jianhua Sun, Hai Gu, Jie Zhang, Guoqing Dai, Bin Li, Zhonggang Sun and Zulei Liang

Materials 2025, 18(16), 3898; https://doi.org/10.3390/ma18163898 - 20 Aug 2025

Viewed by 407

Abstract

The use of additive manufacturing technology for the lightweight design of complex lattice structures is becoming increasingly popular, but research on lattice structure design and strength evaluation still relies on the visual comparison of stress distributions and lacks quantitative assessment data. Given this [...] Read more.

The use of additive manufacturing technology for the lightweight design of complex lattice structures is becoming increasingly popular, but research on lattice structure design and strength evaluation still relies on the visual comparison of stress distributions and lacks quantitative assessment data. Given this perspective, this study explored the effects of structural parameters (relative density, cell size, and sample size) on the compressive strength of diamond lattice structures prepared by Stereolithography (SLA) and revealed the underlying mechanisms through stress distribution simulations and the calculation of characteristic stress distribution parameters (structural efficiency and stress concentration coefficient). The results showed that a greater relative density can increase structural efficiency, but it hardly affects the stress concentration coefficient, and smaller cell sizes and larger sample sizes increase the stress concentration coefficient without affecting the structural efficiency. Lattice structures with a greater relative density, higher structural efficiency, and a larger stress concentration coefficient exhibit higher compressive strength according to the lattice strength formula, which indicates that lattice strength is determined by the product of structural efficiency, stress concentration coefficient, relative density, and material strength. The relevant conclusions could guide the analysis of lattice stress distribution and the design of lattice structures. Full article

(This article belongs to the Section Mechanics of Materials)

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16 pages, 10820 KB

Open AccessArticle

Synergistic Enhancement of Li-O₂ Battery Capacity and Cycle Life Using Carbon Nanochain/Multiwall Carbon Nanotube Composites

by Michael D. Womble, Cynthia Adebayo, Silas Cascio and Michael J. Wagner

Materials 2025, 18(16), 3897; https://doi.org/10.3390/ma18163897 - 20 Aug 2025

Viewed by 421

Abstract

Multiwalled carbon nanotube (MWCNT) Li-O₂ cathodes can achieve high gravimetric capacity. However, the macropores of these cathodes require a relatively large mass of electrolyte to fill, resulting in lower true gravimetric and volumetric capacities. Here we report a simple method to incorporate [...] Read more.

Multiwalled carbon nanotube (MWCNT) Li-O₂ cathodes can achieve high gravimetric capacity. However, the macropores of these cathodes require a relatively large mass of electrolyte to fill, resulting in lower true gravimetric and volumetric capacities. Here we report a simple method to incorporate a mesoporous material, carbon nanochains (CNCs), into the macropores of MWCNTs, resulting in composite cathodes that fully utilize their pore structure to store Li₂O₂ product. The composite cathodes exhibit additional mesopores with an average diameter of ~100 nm. This results in dramatic increases in true gravimetric (21% to 870 mAh/g) and volumetric (>200% to 5664 mAh/cm³) capacities. The composite cathodes demonstrate improved electrochemical reversibility, increasing the cycle life by more than 50%. Full article

(This article belongs to the Special Issue Nanostructured Materials for Environmental Friendly and Related Energy Applications)

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10 pages, 2643 KB

Open AccessArticle

Welding Technology and Heat Treatment Butt-Welded Joints of Thin-Walled Inconel 718 Alloy Tubes

by Patryk Warchoł and Lechosław Tuz

Materials 2025, 18(16), 3896; https://doi.org/10.3390/ma18163896 - 20 Aug 2025

Viewed by 375

Abstract

The subject of this research was the development of technology for welding and the heat treatment of butt-welded joints of thin-walled Inconel 718 alloy tubes, a process based on orbital TIG welding without a filler metal. The developed technology allows favorable conditions to [...] Read more.

The subject of this research was the development of technology for welding and the heat treatment of butt-welded joints of thin-walled Inconel 718 alloy tubes, a process based on orbital TIG welding without a filler metal. The developed technology allows favorable conditions to obtain the appropriate hardness and mechanical properties in the weld area required by AMS 5589. In the tests, the microstructure and mechanical properties were evaluated. Compliance with the requirements was evaluated on the basis of metallographic and mechanical properties tests. The results obtained indicate that the weakest area of the joint is the base material of the thin-walled tube. The welded joints reveal elongation above 10% and tensile strength above 1400 MPa despite the dendritic structure of the weld. In the area of the welded joint, the occurrence of precipitates of the γ’ phase and mainly niobium carbide was revealed. Full article

(This article belongs to the Section Metals and Alloys)

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