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Materials, Volume 17, Issue 7 (April-1 2024) – 259 articles

Cover Story (view full-size image): Sufficient and non-invasive characterization of graphene/silicon interfaces is essential for the practical deployment of graphene-based electronic devices. Terahertz emission spectroscopy and microscopy (TES/LTEM) have emerged as promising techniques for probing the dynamic electronic properties of graphene and enabling extensive graphene mapping on a large scale. By employing ultra-fast femtosecond laser pulses, generated photoelectrons are accelerated by the interface electric field between the graphene and silicon substrate, resulting in THz emission that carries valuable information about the local graphene properties. View this paper
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15 pages, 2543 KiB  
Article
Unraveling Broadband Near-Infrared Luminescence in Cr3+-Doped Ca3Y2Ge3O12 Garnets: Insights from First-Principles Analysis
by Wei Zou, Bibo Lou, Mekhrdod S. Kurboniyon, Maksym Buryi, Farhod Rahimi, Alok M. Srivastava, Mikhail G. Brik, Jing Wang and Chonggeng Ma
Materials 2024, 17(7), 1709; https://doi.org/10.3390/ma17071709 - 8 Apr 2024
Cited by 1 | Viewed by 764
Abstract
In this study, we conducted an extensive investigation into broadband near-infrared luminescence of Cr3+-doped Ca3Y2Ge3O12 garnet, employing first-principles calculations within the density functional theory framework. Our initial focus involved determining the site occupancy of [...] Read more.
In this study, we conducted an extensive investigation into broadband near-infrared luminescence of Cr3+-doped Ca3Y2Ge3O12 garnet, employing first-principles calculations within the density functional theory framework. Our initial focus involved determining the site occupancy of Cr3+ activator ions, which revealed a pronounced preference for the Y3+ sites over the Ca2+ and Ge4+ sites, as evidenced by the formation energy calculations. Subsequently, the geometric structures of the excited states 2E and 4T2, along with their optical transition energies relative to the ground state 4A2 in Ca3Y2Ge3O12:Cr3+, were successfully modeled using the ΔSCF method. Calculation convergence challenges were effectively addressed through the proposed fractional particle occupancy schemes. The constructed host-referred binding energy diagram provided a clear description of the luminescence kinetics process in the garnet, which explained the high quantum efficiency of emission. Furthermore, the accurate prediction of thermal excitation energy yielded insights into the thermal stability of the compound, as illustrated in the calculated configuration coordinate diagram. More importantly, all calculated data were consistently aligned with the experimental results. This research not only advances our understanding of the intricate interplay between geometric and electronic structures, optical properties, and thermal behavior in Cr3+-doped garnets but also lays the groundwork for future breakthroughs in the high-throughput design and optimization of luminescent performance and thermal stability in Cr3+-doped phosphors. Full article
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15 pages, 5456 KiB  
Article
Influence of an Engineered Notch on the Electromagnetic Radiation Performance of NiTi Shape Memory Alloy
by Anu Anand, Rajeev Kumar, Shatrudhan Pandey, S. M. Mozammil Hasnain and Saurav Goel
Materials 2024, 17(7), 1708; https://doi.org/10.3390/ma17071708 - 8 Apr 2024
Viewed by 621
Abstract
This work explores the influence of a pre-engineered notch on the electromagnetic radiation (EMR) parameters in NiTi shape memory alloy (SMA) during tensile tests. The test data showed that the EMR signal fluctuated between oscillatory and exponential, signifying that the specimen’s viscosity damping [...] Read more.
This work explores the influence of a pre-engineered notch on the electromagnetic radiation (EMR) parameters in NiTi shape memory alloy (SMA) during tensile tests. The test data showed that the EMR signal fluctuated between oscillatory and exponential, signifying that the specimen’s viscosity damping coefficient changes during strain hardening. The EMR parameters, maximum EMR amplitude, and average EMR energy release rate remained constant initially but rose sharply with the plastic zone radius with progressive loading. It was postulated that new Frank–Read sources permit dislocation multiplication and increase the number of edge dislocations participating in EMR emissions, leading to a rise in the value of EMR parameters. The study of the correlation between EMR emission parameters and the plastic zone radius before the crack tip is a vital crack growth monitoring tool. An analysis of the interrelationship of the EMR energy release rate at fracture with the elastic strain energy release rate would help develop an innovative approach to assess fracture toughness, a critical parameter for the design and safety of metals. The microstructural analysis of tensile fractures and the interrelation between deformation behaviours concerning the EMR parameters offers a novel and real-time approach to improve the extant understanding of the behaviour of metallic materials. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys)
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20 pages, 3024 KiB  
Review
Approaches for the Treatment and Resource Utilization of Electroplating Sludge
by Song Guo, Huimin Wang, Xiaoming Liu, Zengqi Zhang and Yu Liu
Materials 2024, 17(7), 1707; https://doi.org/10.3390/ma17071707 - 8 Apr 2024
Viewed by 620
Abstract
The disposal of electroplating sludge (ES) is a major challenge for the sustainable development of the electroplating industry. ESs have a significant environmental impact, occupying valuable land resources and incurring high treatment costs, which increases operational expenses for companies. Additionally, the high concentration [...] Read more.
The disposal of electroplating sludge (ES) is a major challenge for the sustainable development of the electroplating industry. ESs have a significant environmental impact, occupying valuable land resources and incurring high treatment costs, which increases operational expenses for companies. Additionally, the high concentration of hazardous substances in ES poses a serious threat to both the environment and human health. Despite extensive scholarly research on the harmless treatment and resource utilization of ES, current technology and processes are still unable to fully harness its potential. This results in inefficient resource utilization and potential environmental hazards. This article analyzes the physicochemical properties of ES, discusses its ecological hazards, summarizes research progress in its treatment, and elaborates on methods such as solidification/stabilization, heat treatment, wet metallurgy, pyrometallurgy, biotechnology, and material utilization. It provides a comparative summary of different treatment processes while also discussing the challenges and future development directions for technologies aimed at effectively utilizing ES resources. The objective of this text is to provide useful information on how to address the issue of ES treatment and promote sustainable development in the electroplating industry. Full article
(This article belongs to the Section Green Materials)
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18 pages, 5555 KiB  
Article
Enhancing Concrete Mechanical Properties through Basalt Fibers and Calcium Sulfate Whiskers: Optimizing Compressive Strength, Elasticity, and Pore Structure
by Junzhi Zhang, Yueming Wang, Xixi Li, Yurong Zhang and Lingjie Wu
Materials 2024, 17(7), 1706; https://doi.org/10.3390/ma17071706 - 8 Apr 2024
Viewed by 555
Abstract
To study the effects of basalt fibers (BFs), calcium sulfate whiskers (CSWs), and modified calcium sulfate whiskers (MCSWs) on the compressive strength and dynamic modulus of elasticity of concrete, this paper utilizes Mercury Intrusion Porosimetry (MIP) to measure the microstructure of concrete and [...] Read more.
To study the effects of basalt fibers (BFs), calcium sulfate whiskers (CSWs), and modified calcium sulfate whiskers (MCSWs) on the compressive strength and dynamic modulus of elasticity of concrete, this paper utilizes Mercury Intrusion Porosimetry (MIP) to measure the microstructure of concrete and calculate the fractal dimension of pore surface area. The results indicate that both CSWs and BFs can increase the compressive strength of concrete. CSWs can enhance the dynamic modulus of elasticity of concrete, while the effect of BFs on the dynamic modulus of elasticity is not significant. The improvement in compressive strength and dynamic modulus of elasticity provided by MCSWs is significantly greater than that provided by CSWs. Both CSWs and BFs can effectively improve the pore structure of concrete and have a significant impact on the surface fractal dimension. CSWs inhibit the formation of ink-bottle pores, while BFs increase the number of ink-bottle pores. Due to the ink-bottle pore effect, the fractal dimension of the capillary pore surface is generally greater than three, lacking fractal characteristics. The compressive strength and dynamic modulus of elasticity of concrete have a good correlation with the fractal dimensions of large pores and transition pores. Full article
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18 pages, 4352 KiB  
Article
Influence of Eggshell Powder on the Properties of Cement-Based Materials
by Gui-Yu Zhang, Seokhoon Oh, Yi Han, Li-Yi Meng, Runsheng Lin and Xiao-Yong Wang
Materials 2024, 17(7), 1705; https://doi.org/10.3390/ma17071705 - 8 Apr 2024
Viewed by 647
Abstract
Replacing cement with industrial by-products is an important way to achieve carbon neutrality in the cement industry. The purpose of this study is to evaluate the effect of eggshell powder on cement hydration properties, and to evaluate its feasibility as a substitute for [...] Read more.
Replacing cement with industrial by-products is an important way to achieve carbon neutrality in the cement industry. The purpose of this study is to evaluate the effect of eggshell powder on cement hydration properties, and to evaluate its feasibility as a substitute for cement. The substitution rates of eggshell powder are 0%, 7.5%, and 15%. Studying the heat of hydration and macroscopic properties can yield the following results. First: The cumulative heat of hydration based on each gram of cementitious material falls as the eggshell powder content rises. This is a result of the eggshell powder’s diluting action. However, the cumulative heat of hydration per gram of cement rises due to the nucleation effect of the eggshell powder. Second: The compressive strengths of ES0, ES7.5, and ES15 samples at 28 days of age are 54.8, 43.4, and 35.5 MPa, respectively. Eggshell powder has a greater negative impact on the compressive strength. The effect of eggshell powder on the speed and intensity of ultrasonic waves has a similar trend. Third: As the eggshell powder content increases, the resistivity gradually decreases. In addition, we also characterize the microscopic properties of the slurry with added eggshell powder. X-ray Diffraction (XRD) shows that, as the age increases from 1 day to 28 days, hemicaboaluminate transforms into monocaboaluminate. As the content of the eggshell powder increases, FTIR analysis finds a slight decrease in the content of CSH. Similarly, thermogravimetric (TG) results also show a decrease in the production of calcium hydroxide. Although the additional nucleation effect of eggshell powder promotes cement hydration and generates more portlandite, it cannot offset the loss of portlandite caused by the decrease in cement. Last: A numerical hydration model is presented for cement–eggshell powder binary blends. The parameters of the hydration model are determined based on hydration heat normalized by cement mass. Moreover, the hydration heat until 28 days is calculated using the proposed model. The strength development of all specimens and all test ages can be expressed as an exponential function of hydration heat. Full article
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17 pages, 32623 KiB  
Article
Superfinishing with Abrasive Films Featuring Discontinuous Surfaces
by Katarzyna Tandecka, Wojciech Kacalak, Maciej Wiliński, Michał Wieczorowski and Thomas G. Mathia
Materials 2024, 17(7), 1704; https://doi.org/10.3390/ma17071704 - 8 Apr 2024
Cited by 1 | Viewed by 486
Abstract
This study introduces innovative designs for abrasive tools aimed at enhancing surface finishing processes. Prototypes consisting of non-continuous abrasive films with discontinuous surface carriers and abrasive layers were developed to improve the efficiency and effectiveness of the smoothing process. Four distinct abrasive films [...] Read more.
This study introduces innovative designs for abrasive tools aimed at enhancing surface finishing processes. Prototypes consisting of non-continuous abrasive films with discontinuous surface carriers and abrasive layers were developed to improve the efficiency and effectiveness of the smoothing process. Four distinct abrasive films with varying nominal grain sizes were fabricated to explore the versatility and efficacy of the prototypes. The results indicate that the incorporation of carrier irregularities significantly influences surface finishing processes, leading to improvements in material removal efficiency and surface quality. Longitudinal discontinuities facilitate faster removal of irregularities from workpiece materials, reducing the risk of deep scratches on surfaces. Additionally, this study highlights the importance of tool motion patterns in optimizing material removal processes and ensuring surface quality. The integration of carrier irregularities with additional oscillatory tool motion shows promise for further improving surface quality. These findings advance our understanding of abrasive machining processes and provide valuable insights for optimizing abrasive tool designs and machining strategies for enhanced surface finishing. Full article
(This article belongs to the Special Issue Advanced Abrasive Processing Technology and Applications)
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12 pages, 2613 KiB  
Article
Analysis of Phase Mismatch for Mercurous Bromide-Based Non-Collinear AOTF Design in Spectral Imaging Applications
by Huijie Zhao, Chi Cheng, Qi Guo, Rui Ma and Yutian Yang
Materials 2024, 17(7), 1703; https://doi.org/10.3390/ma17071703 - 8 Apr 2024
Viewed by 431
Abstract
The spectral and spatial characteristics of Acousto-Optic Tunable Filters (AOTFs), such as a tuning curve, spectral resolution, angular aperture, and diffraction efficiency, are determined by the device’s acousto-optic crystal configuration and piezoelectric transducer. For high-throughput spectral imaging applications, it is essential to enlarge [...] Read more.
The spectral and spatial characteristics of Acousto-Optic Tunable Filters (AOTFs), such as a tuning curve, spectral resolution, angular aperture, and diffraction efficiency, are determined by the device’s acousto-optic crystal configuration and piezoelectric transducer. For high-throughput spectral imaging applications, it is essential to enlarge the spectral bandwidth and angular aperture during the design phase of AOTFs. Thus, phase mismatch due to incident angle or wavelength was studied analytically using phase diagrams in this paper. Additionally, a performance parameter analysis model was established based on the use of mercurous bromide crystals for large angular aperture AOTF device design, and the impact of crystal and transducer design parameters on the spectral bandwidth and angular aperture was evaluated. This also experimentally validates the diffraction capability of AOTFs made from mercurous bromide crystal, which possess a broad spectral transmission ability ranging from visible to long-wave infrared. Full article
(This article belongs to the Special Issue Acousto-Optical Spectral Technologies (2nd Edition))
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20 pages, 11016 KiB  
Article
Low-Frequency Bandgap Characterization of a Locally Resonant Pentagonal Phononic Crystal Beam Structure
by Shengke Zhang, Denghui Qian, Zhiwen Zhang and Haoran Ge
Materials 2024, 17(7), 1702; https://doi.org/10.3390/ma17071702 - 8 Apr 2024
Viewed by 480
Abstract
This paper proposes a local resonance-type pentagonal phononic crystal beam structure for practical engineering applications to achieve better vibration and noise reduction. The energy band, transmission curve, and displacement field corresponding to the vibration modes of the structure are calculated based on the [...] Read more.
This paper proposes a local resonance-type pentagonal phononic crystal beam structure for practical engineering applications to achieve better vibration and noise reduction. The energy band, transmission curve, and displacement field corresponding to the vibration modes of the structure are calculated based on the finite element method and Bloch-Floquet theorem. Furthermore, an analysis is conducted to understand the mechanism behind the generation of bandgaps. The numerical analysis indicates that the pentagonal unit oscillator creates a low-frequency bandgap between 60–70 Hz and 107–130 Hz. Additionally, the pentagonal phononic crystal double-layer beam structure exhibits excellent vibration damping, whereas the single-layer beam has poor vibration damping. The article comparatively analyzes the effects of different parameters on the bandgap range and transmission loss of a pentagonal phononic crystal beam. For instance, increasing the thickness of the lead layer leads to an increase in the width of the bandgap. Similarly, increasing the thickness of the rubber layer, intermediate plate, and total thickness of the phononic crystals results in a bandgap at lower frequencies. By adjusting the parameters, the beam can be optimized for practical engineering purposes. Full article
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13 pages, 4575 KiB  
Article
Effect of Rare Earth Elements on Microstructure and Tensile Behavior of Nb-Containing Microalloyed Steels
by Shi Cheng, Tingping Hou, Yihang Zheng, Chaochao Yin and Kaiming Wu
Materials 2024, 17(7), 1701; https://doi.org/10.3390/ma17071701 - 8 Apr 2024
Viewed by 574
Abstract
The present investigation endeavors to explore the influence of rare earth elements on the strength and plasticity characteristics of low-carbon microalloyed steel under tensile loading conditions. The findings from the conducted tensile tests indicate that the incorporation of rare earths leads to a [...] Read more.
The present investigation endeavors to explore the influence of rare earth elements on the strength and plasticity characteristics of low-carbon microalloyed steel under tensile loading conditions. The findings from the conducted tensile tests indicate that the incorporation of rare earths leads to a notable enhancement in the yield strength, ultimate tensile strength, and ductility properties of the steel. A comparative analysis of the microstructures reveals that the presence of rare earths significantly refines and optimizes the microstructure of the microalloyed steel. This optimization is manifested through a reduction in grain size, diminution of inclusion sizes, and a concomitant rise in their number density. Moreover, the addition of rare earths is observed to foster an increase in the volumetric fraction of carbides within the steel matrix. These multifaceted microstructural alterations collectively contribute to a substantial strengthening of the microalloyed steel. Furthermore, it is elucidated that the synergistic interaction between rare earth elements and both carbon (C) and niobium (Nb) in the steel matrix augments the extent of the Lüders strain region during the tensile deformation of specimens. This phenomenon is accompanied by the effective modification of inclusions by the rare earths, which serves to mitigate stress concentrations at the interfaces between the inclusions and the surrounding matrix. This article systematically evaluates the modification mechanism of rare earth microalloying, which provides a basis for broadening the application of rare earth microalloying in microalloyed steel. Full article
(This article belongs to the Special Issue Mechanical Behavior of Composite Materials (3rd Edition))
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14 pages, 16012 KiB  
Article
Exploring the Influence of Nanocrystalline Structure and Aluminum Content on High-Temperature Oxidation Behavior of Fe-Cr-Al Alloys
by Rajiv Kumar, R. K. Singh Raman, S. R. Bakshi, V. S. Raja and S. Parida
Materials 2024, 17(7), 1700; https://doi.org/10.3390/ma17071700 - 8 Apr 2024
Viewed by 493
Abstract
The present study examines the high-temperature (500–800 °C) oxidation behavior of Fe-10Cr-(3,5) Al alloys and studies the effect of nanocrystalline structure and Al content on their resistance to oxidation. The nanocrystalline (NC) alloy powder was synthesized via planetary ball milling. The prepared NC [...] Read more.
The present study examines the high-temperature (500–800 °C) oxidation behavior of Fe-10Cr-(3,5) Al alloys and studies the effect of nanocrystalline structure and Al content on their resistance to oxidation. The nanocrystalline (NC) alloy powder was synthesized via planetary ball milling. The prepared NC alloy powder was consolidated using spark plasma sintering to form NC alloys. Subsequently, an annealing of the NC alloys was performed to transform them into microcrystalline (MC) alloys. It was observed that the NC alloys exhibit superior resistance to oxidation compared to their MC counterparts at high temperatures. The superior resistance to oxidation of the NC alloys is attributed to their considerably finer grain size, which enhances the diffusion of those elements to the metal–oxide interface that forms the protective oxide layer. Conversely, the coarser grain size in MC alloys limits the diffusion of the oxide-forming components. Furthermore, the Fe-10Cr-5Al alloy showed greater resistance to oxidation than the Fe-10Cr-3Al alloy. Full article
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14 pages, 3253 KiB  
Article
Effect of Chemical Composition on the Thermoplastic Formability and Nanoindentation of Ti-Based Bulk Metallic Glasses
by Mengliang Chen, Liu Zhu, Yingwei Chen, Sheng Dai, Qijie Liu, Na Xue, Weiwei Li, Jinfang Wang, Yingqi Huang, Kaice Yang and Ling Shao
Materials 2024, 17(7), 1699; https://doi.org/10.3390/ma17071699 - 8 Apr 2024
Viewed by 521
Abstract
A series of Ti41Zr25Be34-xNix (x = 4, 6, 8, 10 at.%) and Ti41Zr25Be34-xCux (x = 4, 6, 8 at.%) bulk metallic glasses were investigated to [...] Read more.
A series of Ti41Zr25Be34-xNix (x = 4, 6, 8, 10 at.%) and Ti41Zr25Be34-xCux (x = 4, 6, 8 at.%) bulk metallic glasses were investigated to examine the influence of Ni and Cu content on the viscosity, thermoplastic formability, and nanoindentation of Ti-based bulk metallic glasses. The results demonstrate that Ti41Zr25Be30Ni4 and Ti41Zr25Be26Cu8 amorphous alloys have superior thermoplastic formability among the Ti41Zr25Be34-xNix and Ti41Zr25Be34-xCux amorphous alloys due to their low viscosity in the supercooled liquid region and wider supercooled liquid region. The hardness and modulus exhibit obvious variations with increasing Ni and Cu content in Ti-based bulk metallic glasses, which can be attributed to alterations in atomic density. Optimal amounts of Ni and Cu in Ti-based bulk metallic glasses enhance thermoplastic formability and mechanical properties. The influence of Ni and Cu content on the hardness of Ti-based bulk metallic glasses is discussed from the perspective of the mean atomic distance. Full article
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45 pages, 2604 KiB  
Systematic Review
Biomechanics of the Human Osteochondral Unit: A Systematic Review
by Matteo Berni, Gregorio Marchiori, Massimiliano Baleani, Gianluca Giavaresi and Nicola Francesco Lopomo
Materials 2024, 17(7), 1698; https://doi.org/10.3390/ma17071698 - 8 Apr 2024
Viewed by 910
Abstract
The damping system ensured by the osteochondral (OC) unit is essential to deploy the forces generated within load-bearing joints during locomotion, allowing furthermore low-friction sliding motion between bone segments. The OC unit is a multi-layer structure including articular cartilage, as well as subchondral [...] Read more.
The damping system ensured by the osteochondral (OC) unit is essential to deploy the forces generated within load-bearing joints during locomotion, allowing furthermore low-friction sliding motion between bone segments. The OC unit is a multi-layer structure including articular cartilage, as well as subchondral and trabecular bone. The interplay between the OC tissues is essential in maintaining the joint functionality; altered loading patterns can trigger biological processes that could lead to degenerative joint diseases like osteoarthritis. Currently, no effective treatments are available to avoid degeneration beyond tissues’ recovery capabilities. A thorough comprehension on the mechanical behaviour of the OC unit is essential to (i) soundly elucidate its overall response to intra-articular loads for developing diagnostic tools capable of detecting non-physiological strain levels, (ii) properly evaluate the efficacy of innovative treatments in restoring physiological strain levels, and (iii) optimize regenerative medicine approaches as potential and less-invasive alternatives to arthroplasty when irreversible damage has occurred. Therefore, the leading aim of this review was to provide an overview of the state-of-the-art—up to 2022—about the mechanical behaviour of the OC unit. A systematic search is performed, according to PRISMA standards, by focusing on studies that experimentally assess the human lower-limb joints’ OC tissues. A multi-criteria decision-making method is proposed to quantitatively evaluate eligible studies, in order to highlight only the insights retrieved through sound and robust approaches. This review revealed that studies on human lower limbs are focusing on the knee and articular cartilage, while hip and trabecular bone studies are declining, and the ankle and subchondral bone are poorly investigated. Compression and indentation are the most common experimental techniques studying the mechanical behaviour of the OC tissues, with indentation also being able to provide information at the micro- and nanoscales. While a certain comparability among studies was highlighted, none of the identified testing protocols are currently recognised as standard for any of the OC tissues. The fibril-network-reinforced poro-viscoelastic constitutive model has become common for describing the response of the articular cartilage, while the models describing the mechanical behaviour of mineralised tissues are usually simpler (i.e., linear elastic, elasto-plastic). Most advanced studies have tested and modelled multiple tissues of the same OC unit but have done so individually rather than through integrated approaches. Therefore, efforts should be made in simultaneously evaluating the comprehensive response of the OC unit to intra-articular loads and the interplay between the OC tissues. In this regard, a multidisciplinary approach combining complementary techniques, e.g., full-field imaging, mechanical testing, and computational approaches, should be implemented and validated. Furthermore, the next challenge entails transferring this assessment to a non-invasive approach, allowing its application in vivo, in order to increase its diagnostic and prognostic potential. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Biomaterials)
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20 pages, 25875 KiB  
Article
Investigation on Mechanism of Microstructure Evolution during Multi-Process Hot Forming of GH4169 Superalloy Forging
by Ming-Song Chen, Hong-Wei Cai, Yong-Cheng Lin, Guan-Qiang Wang, Hong-Bin Li, An Liu, Ze-Hao Li and Shan Peng
Materials 2024, 17(7), 1697; https://doi.org/10.3390/ma17071697 - 7 Apr 2024
Viewed by 404
Abstract
Typically, in the manufacturing of GH4169 superalloy forgings, the multi-process hot forming that consists of pre-deformation, heat treatment and final deformation is required. This study focuses on the microstructural evolution throughout hot working processes. Considering that δ phase can promote nucleation and limit [...] Read more.
Typically, in the manufacturing of GH4169 superalloy forgings, the multi-process hot forming that consists of pre-deformation, heat treatment and final deformation is required. This study focuses on the microstructural evolution throughout hot working processes. Considering that δ phase can promote nucleation and limit the growth of grains, a process route was designed, including pre-deformation, aging treatment (AT) to precipitate sufficient δ phases, high temperature holding (HTH) to uniformly heat the forging, and final deformation. The results show that the uneven strain distribution after pre-deformation has a significant impact on the subsequent refinement of the grain microstructure due to the complex coupling relationship between the evolution of the δ phase and recrystallization behavior. After the final deformation, the fine-grain microstructure with short rod-like δ phases as boundaries is easy to form in the region with a large strain of the pre-forging. However, necklace-like mixed grain microstructure is formed in the region with a small strain of the pre-forging. In addition, when the microstructure before final deformation consists of mixed grains, dynamic recrystallization (DRX) nucleation behavior preferentially depends on kernel average misorientation (KAM) values. A large KAM can promote the formation of DRX nuclei. When the KAM values are close, a smaller average grain size of mixed-grain microstructure is more conductive to promote the DRX nucleation. Finally, the interaction mechanisms between δ phase and DRX nucleation are revealed. Full article
(This article belongs to the Special Issue Review and Feature Papers in "Metals and Alloys" Section)
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17 pages, 21736 KiB  
Review
The Precursors Used for Developing Geopolymer Composites for Circular Economy—A Review
by Gabriel Furtos, Doina Prodan, Codruta Sarosi, Dorin Popa, Marioara Moldovan and Kinga Korniejenko
Materials 2024, 17(7), 1696; https://doi.org/10.3390/ma17071696 - 7 Apr 2024
Viewed by 1194
Abstract
Considering recent climate changes, special importance is given to any attempt to depollute and protect the environment. A circular economy seems to be the ideal solution for the valorization of mineral waste, resulting from various industrial branches, by reintroducing them in the process [...] Read more.
Considering recent climate changes, special importance is given to any attempt to depollute and protect the environment. A circular economy seems to be the ideal solution for the valorization of mineral waste, resulting from various industrial branches, by reintroducing them in the process of obtaining alternative building materials, more friendly to the environment. Geopolymers can be considered as a promising option compared to Portland cement. Information about the influence of the composition of the precursors, the influence of the activation system on the mechanical properties or the setting time could lead to the anticipation of new formulations of geopolymers or to the improvement of some of their properties. Reinforcement components, different polymers and expansion agents can positively or negatively influence the properties of geopolymers in the short or long term. Full article
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13 pages, 21069 KiB  
Article
Strength–Ductility Mechanism of CoCrFeMnNi High-Entropy Alloys with Inverse Gradient-Grained Structures
by Jie Chen, Yongqiang Hu, Pengfei Wang, Jingge Li, Yu Zheng, Chengtong Lu, Bohong Zhang, Jiahai Shen and Yu Cao
Materials 2024, 17(7), 1695; https://doi.org/10.3390/ma17071695 - 7 Apr 2024
Viewed by 610
Abstract
The microstructures and mechanical properties of equiatomic CoCrFeMnNi high-entropy alloys (HEAs) treated with various processing parameters of laser surface heat treatment are studied in this paper. The typical inverse gradient-grained structure, which is composed of a hard central layer and a soft surface [...] Read more.
The microstructures and mechanical properties of equiatomic CoCrFeMnNi high-entropy alloys (HEAs) treated with various processing parameters of laser surface heat treatment are studied in this paper. The typical inverse gradient-grained structure, which is composed of a hard central layer and a soft surface layer, can be obtained by laser surface heat treatment. A much narrower gradient layer leads to the highest yield strength by sacrificing ductility when the surface temperature of the laser-irradiated region remains at ~850 °C, whereas the fully recrystallized microstructure, which exists from the top surface layer to the ~1.05 mm depth layer, increases the ductility but decreases the yield strength as the maximum heating temperature rises to ~1050 °C. Significantly, the superior strength–ductility combination can be acquired by controlling the surface temperature of a laser-irradiated surface at ~1000 °C with a scanning speed of ~4 mm/s due to the effect of hetero-deformation-induced strengthening and hardening, as well as the enhanced interaction between dislocation and nanotwins by the hierarchical nanotwins. Therefore, retaining the partial recrystallized microstructure with a relatively high microhardness in the central layer, promoting the generation of hierarchical nanotwins, and increasing the volume proportion of gradient layer can effectively facilitate the inverse gradient-grained CoCrFeMnNi HEAs to exhibit a desirable strength–ductility synergy. Full article
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19 pages, 3331 KiB  
Article
The Friction–Lubrication Effect and Compaction Characteristics of an SMA Asphalt Mixture under Variable Temperature Conditions
by Xia Wu, Xiong Tang, Li Liu, Zhaoyi He and Sheng He
Materials 2024, 17(7), 1694; https://doi.org/10.3390/ma17071694 - 7 Apr 2024
Viewed by 576
Abstract
The aim of this article is to explore the dynamic compaction characteristics of stone mastic asphalt (SMA) and the friction–lubrication effect of internal particles during the superpave gyratory compaction (SGC) process. Firstly, a calculated method for the compaction degree of an asphalt mixture [...] Read more.
The aim of this article is to explore the dynamic compaction characteristics of stone mastic asphalt (SMA) and the friction–lubrication effect of internal particles during the superpave gyratory compaction (SGC) process. Firstly, a calculated method for the compaction degree of an asphalt mixture in the gyratory compaction process was defined based on the multiphase granular volume method. Secondly, the gyratory compaction curves of asphalt mixtures were taken based on this calculation method of compaction degree. The dynamic change law of each compaction index (compaction, percentage of air voids, compaction energy index, etc.) during the compaction process was analysed. Finally, the effects of different initial compaction temperatures and different asphalt content on the friction–lubrication effect and compaction characteristics of asphalt mixtures were studied. Research shows that it is reasonable to define the compaction degree by the ratio of the apparent density of the asphalt mixture to the maximum theoretical density of the asphalt mixture during gyratory compaction. The dynamic prediction equations of the compaction degree K and the compaction energy index CEI with the amount of compaction were established, and could effectively predict the compaction degree, percentage of air voids and compaction energy index CEI. The compaction process of the asphalt mixture needed to go through three phases, including periods of rapid growth, slow growth, and stabilisation, and the compaction degree increased by about 10%, 5%, and 1%, in that order, finally tending towards a stable value. The effect of the initial compaction temperature on the forming compaction degree of the asphalt mixture is significant; therefore, it should be controlled strictly in the compaction construction of asphalt mixtures. When the initial compaction temperature of SMA-13 is about 170 °C, the compaction effect is optimal, and the effect of the increase in the amount of compaction at a later stage on the increase in the compaction degree of the asphalt mixture is very low. With the optimal asphalt content, the friction–lubrication effect between the asphalt and aggregate particles is optimal, because it can effectively form an asphalt film, reducing the frictional resistance of the particles moving each other during the compaction process, and the voids will be embedded and filled with each other, finally producing the best compaction result. Full article
(This article belongs to the Section Construction and Building Materials)
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11 pages, 2674 KiB  
Article
Lightweight 3D Lithiophilic Graphene Aerogel Current Collectors for Lithium Metal Anodes
by Caili Guo, Yongjie Ge, Piao Qing, Yunke Jin, Libao Chen and Lin Mei
Materials 2024, 17(7), 1693; https://doi.org/10.3390/ma17071693 - 7 Apr 2024
Viewed by 745
Abstract
Constructing three-dimensional (3D) current collectors is an effective strategy to solve the hindrance of the development of lithium metal anodes (LMAs). However, the excessive mass of the metallic scaffold structure leads to a decrease in energy density. Herein, lithiophilic graphene aerogels comprising reduced [...] Read more.
Constructing three-dimensional (3D) current collectors is an effective strategy to solve the hindrance of the development of lithium metal anodes (LMAs). However, the excessive mass of the metallic scaffold structure leads to a decrease in energy density. Herein, lithiophilic graphene aerogels comprising reduced graphene oxide aerogels and silver nanowires (rGO-AgNW) are synthesized through chemical reduction and freeze-drying techniques. The rGO aerogels with large specific surface areas effectively mitigate local current density and delay the formation of lithium dendrites, and the lithiophilic silver nanowires can provide sites for the uniform deposition of lithium. The rGO-AgNW/Li symmetric cell presents a stable cycle of about 2000 h at 1 mA cm−2. When coupled with the LiFePO4 cathode, the assembled full cells exhibit outstanding cycle stability and rate performance. Lightweight rGO-AgNW aerogels, as the host for lithium metal, can significantly improve the energy density of lithium metal anodes. Full article
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9 pages, 1992 KiB  
Article
Optical Temperature-Sensing Performance of La2Ce2O7:Ho3+ Yb3+ Powders
by Jiameng Chao, Hui Lin, Dechao Yu, Ruijin Hong, Zhaoxia Han, Chunxian Tao and Dawei Zhang
Materials 2024, 17(7), 1692; https://doi.org/10.3390/ma17071692 - 7 Apr 2024
Viewed by 480
Abstract
In this paper, La2Ce2O7 powders co-activated by Ho3+ and Yb3+ were synthesized by a high temperature solid-state reaction. Both Ho3+ and Yb3+ substitute the La3+ sites in the La2Ce2O [...] Read more.
In this paper, La2Ce2O7 powders co-activated by Ho3+ and Yb3+ were synthesized by a high temperature solid-state reaction. Both Ho3+ and Yb3+ substitute the La3+ sites in the La2Ce2O7 lattice, where the Ho3+ concentration is 0.5 at.% and the Yb3+ concentration varies in the range of 10~18% at.%. Pumped by a 980 nm laser, the up-conversion (UC) green emission peak at 547 nm and the red emission at 661 nm were detected. When the doping concentration of Ho3+ and Yb3+ are 0.5 at.% and 14% at.%, respectively, the UC emission reaches the strongest intensity. The temperature-sensing performance of La2Ce2O7:Ho3+ with Yb3+ was studied in the temperature range of 303–483 K, where the highest relative sensitivity (Sr) is 0.0129 K−1 at 483 K. The results show that the powder La2Ce2O7:Ho3+, Yb3+ can be a potential candidate for remote temperature sensors. Full article
(This article belongs to the Section Materials Physics)
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19 pages, 9174 KiB  
Review
Clays and Wound Healing
by Guangjian Tian, Zhou Wang, Zongwang Huang, Zuyan Xie, Lu Xia and Yi Zhang
Materials 2024, 17(7), 1691; https://doi.org/10.3390/ma17071691 - 7 Apr 2024
Viewed by 792
Abstract
Aluminosilicates, such as montmorillonite, kaolinite, halloysite, and diatomite, have a uniform bidimensional structure, a high surface-to-volume ratio, inherent stiffness, a dual charge distribution, chemical inertness, biocompatibility, abundant active groups on the surface, such as silanol (Si-OH) and/or aluminol (Al-OH) groups. These compounds are [...] Read more.
Aluminosilicates, such as montmorillonite, kaolinite, halloysite, and diatomite, have a uniform bidimensional structure, a high surface-to-volume ratio, inherent stiffness, a dual charge distribution, chemical inertness, biocompatibility, abundant active groups on the surface, such as silanol (Si-OH) and/or aluminol (Al-OH) groups. These compounds are on the list of U.S. Food and Drug Administration-approved active compounds and excipients and are used for various medicinal products, such as wound healing agents, antidiarrheals, and cosmetics. This review summarizes the wound healing mechanisms related to the material characteristics and the chemical components. Numerous wound dressings with different active components and multiple forms have been studied. Then, medicinal mineral resources for use in hemostatic materials can be developed. Full article
(This article belongs to the Special Issue Materials for Hard Tissue Repair and Regeneration (Third Volume))
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15 pages, 5096 KiB  
Article
Research on the Synthesis of Zinc–Ammonium Phosphate Using Galvanic Waste Sludge as a Source of Zinc
by Claudia Mona Morgovan, Anda Ioana Gratiela Petrehele, Gabriela Elena Badea, Alexandrina Fodor, Monica Toderaș and Eleonora Marian
Materials 2024, 17(7), 1690; https://doi.org/10.3390/ma17071690 - 7 Apr 2024
Viewed by 578
Abstract
This paper presents the extraction of zinc ions from waste resulting from the galvanic industry, such as sludge from acid zinc electroplating baths, and their revaluation in mineral fertilizer as zinc–ammonium phosphate. The purpose of this work is to extract zinc ions from [...] Read more.
This paper presents the extraction of zinc ions from waste resulting from the galvanic industry, such as sludge from acid zinc electroplating baths, and their revaluation in mineral fertilizer as zinc–ammonium phosphate. The purpose of this work is to extract zinc ions from the sludge that forms directly in the zinc bath, which can only contain zinc and small amounts of iron, to revalorize zinc into the form of zinc–ammonium phosphate. The process of obtaining zinc–ammonium phosphate is presented using waste sludge from the galvanic industry. In order to obtain zinc–ammonium phosphate, the solution resulting from the dissolution of the sludge with a 20% hydrochloric acid solution was used in reaction with diammonium phosphate and a 25% ammonia solution. After the chemical analysis of the obtained products, zinc–ammonium phosphate was characterized using X-ray powder diffraction, infrared FT-IR spectroscopy and electronic microscopy (SEM) analysis. The results obtained indicate a promising approach to sustainable resource utilization in the production of zinc–ammonium phosphate. Full article
(This article belongs to the Section Green Materials)
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21 pages, 5250 KiB  
Article
Investigation of the Influence of Machining Parameters and Surface Roughness on the Wettability of the Al6082 Surfaces Produced with WEDM
by Dimitrios Skondras-Giousios, Panagiotis Karmiris-Obratański, Magdalena Jarosz and Angelos P. Markopoulos
Materials 2024, 17(7), 1689; https://doi.org/10.3390/ma17071689 - 7 Apr 2024
Viewed by 530
Abstract
Electrical Discharge Machining (EDM) is a non-conventional machining technique, capable of processing any kind of conductive material. Recently, it has been successfully utilized for producing hydrophobic characteristics in inherently hydrophilic metallic materials. In this work, Wire Electrical Discharge Machining (WEDM) was utilized for [...] Read more.
Electrical Discharge Machining (EDM) is a non-conventional machining technique, capable of processing any kind of conductive material. Recently, it has been successfully utilized for producing hydrophobic characteristics in inherently hydrophilic metallic materials. In this work, Wire Electrical Discharge Machining (WEDM) was utilized for producing hydrophobic characteristics on the surface of the aluminum alloy 6082, and various parameters that can affect wettability were investigated. Adopting an orthogonal Taguchi approach, the effects of the process parameter values of peak current, pulse-on time, and gap voltage on the contact angles of the machined surfaces were investigated. After machining, all samples were observed to have obtained hydrophobic properties, reaching contact angles up to 132°. The peak current was identified as the most influential parameter regarding the contact angle, while the gap voltage was the less influential parameter. A contact angle variation of 30° was observed throughout different combinations of machining parameters. Each combination of the machining parameters resulted in a distinct surface morphology. The samples with moderate roughness values (3.4 μm > Sa > 5.7 μm) were found to be more hydrophobic than the samples with high or low values, where the contact angle was measured under 115°. In addition, the finite element modeling of the experimental setup, with parametric surfaces of uniform random and Perlin noise types of roughness, was implemented. Time dependent simulations coupling phase field and laminar flow for the modelingof the wetting of surfaces with different surface roughness characteristics showed that an increase in the Sa roughness and total wetted area can lead to an increase in the contact angle. The combination of experimental and computational results suggests that the complexity of the wettability outcomes of aluminum alloy surfaces processed with WEDM lies in the interplay between variations of the surface chemical composition, roughness, micro/nano morphology, and the surface capability of forming a composite air/water interface. Full article
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22 pages, 8640 KiB  
Article
Effect of Cryogenic Treatments on Hardness, Fracture Toughness, and Wear Properties of Vanadis 6 Tool Steel
by Venu Yarasu, Peter Jurci, Jana Ptacinova, Ivo Dlouhy and Jakub Hornik
Materials 2024, 17(7), 1688; https://doi.org/10.3390/ma17071688 - 7 Apr 2024
Viewed by 521
Abstract
The ability of cryogenic treatment to improve tool steel performance is well established; however, the selection of optimal heat treatment is pivotal for cost reduction and extended tool life. This investigation delves into the influence of distinct cryogenic and tempering treatments on the [...] Read more.
The ability of cryogenic treatment to improve tool steel performance is well established; however, the selection of optimal heat treatment is pivotal for cost reduction and extended tool life. This investigation delves into the influence of distinct cryogenic and tempering treatments on the hardness, fracture toughness, and tribological properties of Vanadis 6 tool steel. Emphasis was given to comprehending wear mechanisms, wear mode identification, volume loss estimation, and detailed characterization of worn surfaces through scanning electron microscopy coupled with energy dispersive spectroscopy and confocal microscopy. The findings reveal an 8–9% increase and a 3% decrease in hardness with cryogenic treatment compared to conventional treatment when tempered at 170 °C and 530 °C, respectively. Cryotreated specimens exhibit an average of 15% improved fracture toughness after tempering at 530 °C compared to conventional treatment. Notably, cryogenic treatment at −140 °C emerges as the optimum temperature for enhanced wear performance in both low- and high-temperature tempering scenarios. The identified wear mechanisms range from tribo-oxidative at lower contacting conditions to severe delaminative wear at intense contacting conditions. These results align with microstructural features, emphasizing the optimal combination of reduced retained austenite and the highest carbide population density observed in −140 °C cryogenically treated steel. Full article
(This article belongs to the Special Issue Heat Treatment of Metallic Materials in Modern IndustryVolume II)
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30 pages, 862 KiB  
Review
Applications of Plasma Technologies in Recycling Processes
by Reinosuke Kusano and Yukihiro Kusano
Materials 2024, 17(7), 1687; https://doi.org/10.3390/ma17071687 - 7 Apr 2024
Viewed by 1791
Abstract
Plasmas are reactive ionised gases, which enable the creation of unique reaction fields. This allows plasmas to be widely used for a variety of chemical processes for materials, recycling among others. Because of the increase in urgency to find more sustainable methods of [...] Read more.
Plasmas are reactive ionised gases, which enable the creation of unique reaction fields. This allows plasmas to be widely used for a variety of chemical processes for materials, recycling among others. Because of the increase in urgency to find more sustainable methods of waste management, plasmas have been enthusiastically applied to recycling processes. This review presents recent developments of plasma technologies for recycling linked to economical models of circular economy and waste management hierarchies, exemplifying the thermal decomposition of organic components or substances, the recovery of inorganic materials like metals, the treatment of paper, wind turbine waste, and electronic waste. It is discovered that thermal plasmas are most applicable to thermal processes, whereas nonthermal plasmas are often applied in different contexts which utilise their chemical selectivity. Most applications of plasmas in recycling are successful, but there is room for advancements in applications. Additionally, further perspectives are discussed. Full article
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20 pages, 5385 KiB  
Article
Nanoparticle Metrology of Silicates Using Time-Resolved Multiplexed Dye Fluorescence Anisotropy, Small Angle X-ray Scattering, and Molecular Dynamics Simulations
by Daniel Doveiko, Alan R. G. Martin, Vladislav Vyshemirsky, Simon Stebbing, Karina Kubiak-Ossowska, Olaf Rolinski, David J. S. Birch and Yu Chen
Materials 2024, 17(7), 1686; https://doi.org/10.3390/ma17071686 - 7 Apr 2024
Viewed by 705
Abstract
We investigate the nanometrology of sub-nanometre particle sizes in industrially manufactured sodium silicate liquors at high pH using time-resolved fluorescence anisotropy. Rather than the previous approach of using a single dye label, we investigate and quantify the advantages and limitations of multiplexing two [...] Read more.
We investigate the nanometrology of sub-nanometre particle sizes in industrially manufactured sodium silicate liquors at high pH using time-resolved fluorescence anisotropy. Rather than the previous approach of using a single dye label, we investigate and quantify the advantages and limitations of multiplexing two fluorescent dye labels. Rotational times of the non-binding rhodamine B and adsorbing rhodamine 6G dyes are used to independently determine the medium microviscosity and the silicate particle radius, respectively. The anisotropy measurements were performed on the range of samples prepared by diluting the stock solution of silicate to concentrations ranging between 0.2 M and 2 M of NaOH and on the stock solution at different temperatures. Additionally, it was shown that the particle size can also be measured using a single excitation wavelength when both dyes are present in the sample. The recovered average particle size has an upper limit of 7.0 ± 1.2 Å. The obtained results were further verified using small-angle X-ray scattering, with the recovered particle size equal to 6.50 ± 0.08 Å. To disclose the impact of the dye label on the measured complex size, we further investigated the adsorption state of rhodamine 6G on silica nanoparticles using molecular dynamics simulations, which showed that the size contribution is strongly impacted by the size of the nanoparticle of interest. In the case of the higher radius of curvature (less curved) of larger particles, the size contribution of the dye label is below 10%, while in the case of smaller and more curved particles, the contribution increases significantly, which also suggests that the particles of interest might not be perfectly spherical. Full article
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18 pages, 7243 KiB  
Article
Processing of Thin Films Based on Cellulose Nanocrystals and Biodegradable Polymers by Space-Confined Solvent Vapor Annealing and Morphological Characteristics
by Lacrimioara Senila, Ioan Botiz, Cecilia Roman, Dorina Simedru, Monica Dan, Irina Kacso, Marin Senila and Otto Todor-Boer
Materials 2024, 17(7), 1685; https://doi.org/10.3390/ma17071685 - 7 Apr 2024
Viewed by 633
Abstract
L-poly(lactic acid), poly(3-hydroxybutyrate), and poly-hydroxybutyrate-co-hydroxyvalerate are biodegradable polymers that can be obtained from renewable biomass sources. The aim of this study was to develop three types of environmentally friendly film biocomposites of altered microstructure by combining each of the above-mentioned polymers [...] Read more.
L-poly(lactic acid), poly(3-hydroxybutyrate), and poly-hydroxybutyrate-co-hydroxyvalerate are biodegradable polymers that can be obtained from renewable biomass sources. The aim of this study was to develop three types of environmentally friendly film biocomposites of altered microstructure by combining each of the above-mentioned polymers with cellulose nanocrystal fillers and further processing the resulting materials via space-confined solvent vapor annealing. Cellulose was previously obtained from renewable biomass and further converted to cellulose nanocrystals by hydrolysis with the lactic acid. The solutions of biodegradable polymers were spin-coated onto solid substrates before and after the addition of cellulose nanocrystals. The obtained thin film composites were further processed via space-confined solvent vapor annealing to eventually favor their crystallization and, thus, to alter the final microstructure. Indeed, atomic force microscopy studies have revealed that the presence of cellulose nanocrystals within a biodegradable polymer matrix promoted the formation of large crystalline structures exhibiting fractal-, spherulitic- or needle-like morphologies. Full article
(This article belongs to the Special Issue Sustainable Materials from Industrial Waste)
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23 pages, 4430 KiB  
Article
Study on Plastic Constitutive Relation and Ductile Fracture Criterion of AM60B Magnesium Alloy
by Qin Yang, Bin Jiang, Liang Gao, Yuyang Gao, Bin Liang, Sha Lan, Zeng Qin, Wenjun Zou, Fengying Yang and Fusheng Pan
Materials 2024, 17(7), 1684; https://doi.org/10.3390/ma17071684 - 7 Apr 2024
Viewed by 776
Abstract
It is currently a challenge to accurately predict the deformation and fracture behavior of metal parts in automobile crashes. Many studies have shown that the deformation and fracture behavior of materials are significantly affected by the stress state during automobile crashes with complex [...] Read more.
It is currently a challenge to accurately predict the deformation and fracture behavior of metal parts in automobile crashes. Many studies have shown that the deformation and fracture behavior of materials are significantly affected by the stress state during automobile crashes with complex stress state characteristics. In order to further promote the application of die-cast magnesium alloys in automobiles, it is particularly important to study the material deformation and fracture behavior of die-cast magnesium alloys. In this paper, the mechanical properties of the AM60B die-cast magnesium alloy sheet under four stress states (shear, tension, R10 notch tension, and cupping) were designed and tested. Based on the von Mises isotropic constitutive model and Swift weighted Hockett–Sherby hardening model, the plastic constitutive model of die-cast magnesium alloy was established. Based on the plastic model and the fracture model (JC, MMC, and DIEM) considering the influence of three stress states, the deformation and fracture behavior of the AM60B die-cast magnesium alloy front-end members in three-point bending were predicted by experiments and finite element simulation. The experimental results show that the deformation mode and loading–displacement curve trend of the AM60B die-cast magnesium alloy front members are the same, the crack initiation point and crack initiation time are the same, and the crack shape is similar. The results show that the complex stress state constitutive model parameters and the DIEM fracture model obtained in this paper can accurately predict the deformation and fracture failure behavior of the AM60B die-cast magnesium alloy sheet. Full article
(This article belongs to the Section Metals and Alloys)
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21 pages, 11311 KiB  
Article
Investigating the Impact Behavior of Carbon Fiber/Polymethacrylimide (PMI) Foam Sandwich Composites for Personal Protective Equipment
by Xinyu Zhang, Miao Tian, Jun Li and Xinggang Chen
Materials 2024, 17(7), 1683; https://doi.org/10.3390/ma17071683 - 6 Apr 2024
Viewed by 620
Abstract
To improve the shock resistance of personal protective equipment and reduce casualties due to shock wave accidents, this study prepared four types of carbon fiber/polymethacrylimide (PMI) foam sandwich panels with different face/back layer thicknesses and core layer densities and subjected them to quasi-static [...] Read more.
To improve the shock resistance of personal protective equipment and reduce casualties due to shock wave accidents, this study prepared four types of carbon fiber/polymethacrylimide (PMI) foam sandwich panels with different face/back layer thicknesses and core layer densities and subjected them to quasi-static compression, low-speed impact, high-speed impact, and non-destructive tests. The mechanical properties and energy absorption capacities of the impact-resistant panels, featuring ceramic/ultra-high molecular-weight polyethylene (UHMWPE) and carbon fiber/PMI foam structures, were evaluated and compared, and the feasibility of using the latter as a raw material for personal impact-resistant equipment was also evaluated. For the PMI sandwich panel with a constant total thickness, increasing the core layer density and face/back layer thickness enhanced the energy absorption capacity, and increased the peak stress of the face layer. Under a constant strain, the energy absorption value of all specimens increased with increasing impact speed. When a 10 kg hammer impacted the specimen surface at a speed of 1.5 m/s, the foam sandwich panels retained better integrity than the ceramic/UHMWPE panel. The results showed that the carbon fiber/PMI foam sandwich panels were suitable for applications that require the flexible movement of the wearer under shock waves, and provide an experimental basis for designing impact-resistant equipment with low weight, high strength, and high energy absorption capacities. Full article
(This article belongs to the Special Issue Recent Progress in Functional Materials and Their Applications)
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18 pages, 3910 KiB  
Article
The Characterization of a Biodegradable Mg Alloy after Powder Bed Fusion with Laser Beam/Metal Processing for Custom Shaped Implants
by Doina Raducanu, Vasile Danut Cojocaru, Anna Nocivin, Silviu Iulian Drob, Radu Emil Hendea, Doina Stanciu, Steliana Ivanescu, Vlad Andrei Raducanu, Nicolae Serban, Elisabeta Mirela Cojocaru and Radu Septimiu Campian
Materials 2024, 17(7), 1682; https://doi.org/10.3390/ma17071682 - 6 Apr 2024
Viewed by 608
Abstract
A new Mg-Zn-Zr-Ca alloy in a powder state, intended to be used for custom shaped implants, was obtained via a mechanical alloying method from pure elemental powder. Further, the obtained powder alloy was processed by a PBF-LB/M (powder bed fusion with laser beam/of [...] Read more.
A new Mg-Zn-Zr-Ca alloy in a powder state, intended to be used for custom shaped implants, was obtained via a mechanical alloying method from pure elemental powder. Further, the obtained powder alloy was processed by a PBF-LB/M (powder bed fusion with laser beam/of metal) procedure to obtain additive manufactured samples for small biodegradable implants. A series of microstructural, mechanical and corrosion analyses were performed. The SEM (scanning electron microscopy) analysis of the powder alloy revealed a good dimensional homogeneity, with a uniform colour, no agglutination and almost rounded particles, suitable for the powder bed fusion procedure. Further, the PBF-LB/M samples revealed a robust and unbreakable morphology, with a suitable porosity (that can reproduce that of cortical bone) and without an undesirable balling effect. The tested Young’s modulus of the PBF-LB/M samples, which was 42 GPa, is close to that of cortical bone, 30 GPa. The corrosion tests that were performed in PBS (Phosphate-buffered saline) solution, with three different pH values, show that the corrosion parameters have a satisfactory evolution comparative to the commercial ZK 60 alloy. Full article
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16 pages, 6304 KiB  
Article
The Influence of Various Welding Methods on the Microstructure and Mechanical Properties of 316Ti Steel
by Piotr Noga, Tomasz Skrzekut, Maciej Wędrychowicz, Marek St. Węglowski and Marcel Wiewióra
Materials 2024, 17(7), 1681; https://doi.org/10.3390/ma17071681 - 6 Apr 2024
Viewed by 533
Abstract
Austenitic stainless steels are very popular due to their high strength properties, ductility, excellent corrosion resistance and work hardening. This paper presents the test results for joining AISI 316Ti austenitic steel. The technologies used for joining were the most popular welding techniques such [...] Read more.
Austenitic stainless steels are very popular due to their high strength properties, ductility, excellent corrosion resistance and work hardening. This paper presents the test results for joining AISI 316Ti austenitic steel. The technologies used for joining were the most popular welding techniques such as TIG (welding with a non-consumable electrode in the shield of inert gases), MIG (welding with a consumable electrode in the shield of inert gases) as well as high-energy EBW welding (Electron Beam Welding) and plasma PAW (plasma welding). Microstructural examinations in the face, center and root areas of the weld revealed different contents of delta ferrite with skeletal or lathy ferrite morphology. Additionally, the presence of columnar grains at the fusion line and equiaxed grains in the center of the welds was found. Microstructural, X-ray and ferroscope tests showed the presence of different delta ferrite contents depending on the technology used. The highest content of delta ferrite was found in the TIG and PAW connectors, approximately 5%, and the lowest in the EBW connector, approximately 2%. Based on the tests carried out on the mechanical properties, it was found that the highest properties were achieved by the MIG joint (Rm, 616, Rp0.2 = 335 MPa), while the lowest were achieved by the PAW joint (Rm = 576, Rp0.2 = 315 MPa). Full article
(This article belongs to the Special Issue Advances in Welding Process and Materials (2nd Edition))
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16 pages, 2371 KiB  
Article
Friction Reduction Achieved by Ultraviolet Illumination on TiO2 Surface
by Xiao Sang, Ke Han, Manfu Zhu and Liran Ma
Materials 2024, 17(7), 1680; https://doi.org/10.3390/ma17071680 - 6 Apr 2024
Viewed by 626
Abstract
Controlling friction by light field is a low-cost, low-energy, non-polluting method. By applying ultraviolet light on the surface of photosensitive materials, the properties of the friction pairs or lubricant can be influenced, thus achieving the purpose of reducing friction. In this study, TiO [...] Read more.
Controlling friction by light field is a low-cost, low-energy, non-polluting method. By applying ultraviolet light on the surface of photosensitive materials, the properties of the friction pairs or lubricant can be influenced, thus achieving the purpose of reducing friction. In this study, TiO2, an inorganic photosensitive material, was selected to investigate the modulating effect of light fields on friction lubrication when using polyalphaolefin (PAO) base oil as a lubricant, and the modulation law of light fields on the friction lubrication behavior was investigated under different loads (1–8 N), different speeds (20–380 mm/s), and different viscosities (10.1–108.6 mPa·s) of PAO base oil. The experimental results showed that light treatment could reduce the friction coefficient of PAO4 base oil lubrication from 0.034 to 0.016, with a reduction of 52.9% under conditions of 3 N-load and 56.5 mm/s-speed, and the best regulation effect could be achieved under the mixed lubrication condition. After TiO2 was treated with ultraviolet light, due to its photocatalytic property, PAO molecules were oxidized and adsorbed on the TiO2 surface to form an adsorption layer, which avoided the direct contact of rough peaks and thus reduced the friction coefficient. This study combines photosensitivity, photocatalysis, and friction, presenting a method to reduce the friction coefficient by applying a light field without changing the friction pairs or lubricants, which provides a new direction for friction modulation and gives new ideas for practical applications. Full article
(This article belongs to the Special Issue Study of Interfacial Tribology and Friction)
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