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Materials, Volume 15, Issue 15 (August-1 2022) – 381 articles

Cover Story (view full-size image): Innovation in surface modification techniques is essential to develop orthopedic materials with optimal properties at the biomaterial–bone interface. Ti-33.6% Nb-4% Sn (TiNbSn) alloys are excellent new titanium alloys with a low Young’s modulus, high tensile strength, and with gradient functional properties of thermally adjustable Young’s modulus and strength. Titanium dioxide, when obtained by the anodic oxidation of TiNbSn alloys, improves bone affinity and provides antibacterial performance through photocatalytic activity. The introduction of anodic oxidation technology for TiNbSn alloys is expected to reduce orthopedic-surgery-related complications, such as loosening, stress shielding, and infection after joint replacement surgery. View this paper
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17 pages, 5751 KiB  
Article
Vacancy Energetics and Diffusivities in the Equiatomic Multielement Nb-Mo-Ta-W Alloy
by Xinran Zhou, Sicong He and Jaime Marian
Materials 2022, 15(15), 5468; https://doi.org/10.3390/ma15155468 - 08 Aug 2022
Cited by 10 | Viewed by 1893
Abstract
In this work, we study vacancy energetics in the equiatomic Nb-Mo-Ta-W alloy, especially vacancy formation and migration energies, using molecular statics calculations based on a spectral neighbor analysis potential specifically developed for Nb-Mo-Ta-W. We consider vacancy properties in bulk environments as well as [...] Read more.
In this work, we study vacancy energetics in the equiatomic Nb-Mo-Ta-W alloy, especially vacancy formation and migration energies, using molecular statics calculations based on a spectral neighbor analysis potential specifically developed for Nb-Mo-Ta-W. We consider vacancy properties in bulk environments as well as near edge dislocation cores, including the effect of short-range order (SRO) by preparing supercells through Metropolis Monte-Carlo relaxations and temperature on the calculation. The nudged elastic band (NEB) method is applied to study vacancy migration energies. Our results show that both vacancy formation energies and vacancy migration energies are statistically distributed with a wide spread, on the order of 1.0 eV in some cases, and display a noticeable dependence on SRO. We find that, in some cases, vacancies can form with very low energies at edge dislocation cores, from which we hypothesize the formation of stable ‘superjogs’ on edge dislocation lines. Moreover, the large spread in vacancy formation energies results in an asymmetric thermal sampling of the formation energy distribution towards lower values. This gives rise to effective vacancy formation energies that are noticeably lower than the distribution averages. We study the effect that this phenomenon has on the vacancy diffusivity in the alloy and discuss the implications of our findings on the structural features of Nb-Mo-Ta-W. Full article
(This article belongs to the Special Issue Compositional Complex Alloys: From Amorphous to High-Entropy)
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9 pages, 2593 KiB  
Article
Influence of Scale Effect on Strength and Deformation Characteristics of Rockfill Materials
by Hongxing Han, Jing Li, Jicun Shi and Cuina Yang
Materials 2022, 15(15), 5467; https://doi.org/10.3390/ma15155467 - 08 Aug 2022
Cited by 1 | Viewed by 1409
Abstract
The hybrid method was adopted to model the original gradation of rockfill materials. According to the specification requirements, three simulated gradations of rockfill materials have been obtained. By the same token, the corresponding maximum particle sizes are 20 mm, 40 mm and 60 [...] Read more.
The hybrid method was adopted to model the original gradation of rockfill materials. According to the specification requirements, three simulated gradations of rockfill materials have been obtained. By the same token, the corresponding maximum particle sizes are 20 mm, 40 mm and 60 mm, respectively. With samples prepared under the same criterion of relative density, the scale effect on strength and deformation characteristics of the rockfill materials were studied by large-scale and consolidated-drained triaxial compression tests. The results show that when the confining pressure is higher, the peak deviator stress decreases with the increase of the maximum particle size. With the increase of the maximum particle size, the cohesion of rockfill materials gradually increases and the internal friction angle gradually decreases. Under the condition of the same maximum particle size, with the increase of confining pressure, the volume strain at the phase transition increases gradually, while the stress ratio at the phase transition decreases. Under the same confining pressure, the larger the particle size is, the smaller the volume strain becomes and the lower the stress ratio at the phase transition is. Therefore, the research results can provide a theoretical basis for establishing the constitutive model of rockfill materials considering the scale effect. Full article
(This article belongs to the Collection Advanced Civil Engineering Materials: From Synthesis to Application)
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29 pages, 3037 KiB  
Review
Cementitious Grouts for Semi-Flexible Pavement Surfaces—A Review
by Muhammad Imran Khan, Muslich Hartadi Sutanto, Nur Izzi Md. Yusoff, Salah E. Zoorob, Waqas Rafiq, Mujahid Ali, Roman Fediuk and Nikolai Ivanovich Vatin
Materials 2022, 15(15), 5466; https://doi.org/10.3390/ma15155466 - 08 Aug 2022
Cited by 13 | Viewed by 3123
Abstract
The hybrid type of pavement called semi-flexible or grouted macadam has gained popularity over the last few decades in various countries, as it provides significant advantages over both rigid and conventional flexible pavements. The semi-flexible pavement surface consists of an open-graded asphalt mixture [...] Read more.
The hybrid type of pavement called semi-flexible or grouted macadam has gained popularity over the last few decades in various countries, as it provides significant advantages over both rigid and conventional flexible pavements. The semi-flexible pavement surface consists of an open-graded asphalt mixture with high percentage voids into which flowable cementitious slurry is allowed to penetrate due to gravitational effect. Several researchers have conducted laboratory, as well as field, experiments on evaluating the performance of semi-flexible layers using different compositions of cementitious grouts. The composition of grouts (i.e., water/cement ratio, superplasticizer, polymers, admixtures, and other supplementary materials) has a significant effect on the performance of grouts and semi-flexible mixtures. A comprehensive review of cementitious grouts and their effect on the performance of semi-flexible layers are presented and summarized in this review study. The effect of byproducts and other admixtures/additives on the mechanical properties of grouts are also discussed. Finally, recommendations on the composition of cementitious grouts have been suggested. Full article
(This article belongs to the Special Issue Sustainable Cementitious Materials for Civil and Transportation Engineering)
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22 pages, 4269 KiB  
Article
Analysis of Cutting Stability of a Composite Variable-Section Boring Bar with a Large Length-to-Diameter Ratio Considering Internal Damping
by Jingmin Ma, Jianfeng Xu, Longfei Li, Xingguang Liu and Ming Gao
Materials 2022, 15(15), 5465; https://doi.org/10.3390/ma15155465 - 08 Aug 2022
Cited by 3 | Viewed by 1415
Abstract
Chattering in composite deep-hole boring can directly affect surface processing quality and efficiency and has always been a research hotspot in machining mechanics. In this study, based on Euler–Bernoulli beam theory, the fine control equations for the cutting stability of composite variable-section boring [...] Read more.
Chattering in composite deep-hole boring can directly affect surface processing quality and efficiency and has always been a research hotspot in machining mechanics. In this study, based on Euler–Bernoulli beam theory, the fine control equations for the cutting stability of composite variable-section boring bars were established using the Hamilton principle, in which the sectional change and internal damping of the material were considered. Next, using the Galerkin method and semi-discrete method, the effects of the taper ratio, damping ratio, length-to-diameter ratio, and ply angle on the free vibration characteristics and cutting stability were analyzed in detail. The results show that at a low damping ratio, both the first-order inherent frequency and boring stability can be enhanced with the increase in the taper ratio; at a large damping ratio, increasing the taper ratio can reduce the first-order inherent frequency and boring stability. Finally, the effects of the sectional change on the inherent frequency, displacement response, and convergence were analyzed. A numerical simulation was performed for the model reliability validation. The present research results can provide a theoretical basis and technical guidance for analyzing the cutting stability and fine control of composite variable-section boring bars with large length-to-diameter ratios. Full article
(This article belongs to the Special Issue Manufacturing and Fatigue Properties of Materials)
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12 pages, 2865 KiB  
Article
Effect of P2O5 and Na2O on the Solubility of Molybdenum and Structural Features in Borosilicate Glass
by Hao Liu, Yongchang Zhu, Jichuan Huo, Zhu Cui, Xingquan Zhang, Qin Jiang, Debo Yang and Baojian Meng
Materials 2022, 15(15), 5464; https://doi.org/10.3390/ma15155464 - 08 Aug 2022
Cited by 2 | Viewed by 1574
Abstract
In this paper, the effect of doping phosphorus in a borosilicate glass matrix to improve the solubility of Mo was investigated by X-ray diffraction (XRD), Raman, and solid-state nuclear magnetic resonance (NMR) spectroscopy, and the effectiveness of Na content on P species inhibiting [...] Read more.
In this paper, the effect of doping phosphorus in a borosilicate glass matrix to improve the solubility of Mo was investigated by X-ray diffraction (XRD), Raman, and solid-state nuclear magnetic resonance (NMR) spectroscopy, and the effectiveness of Na content on P species inhibiting the growth of the crystallization of Mo was assessed. The results indicate that phosphate-doped borosilicate glass can host 4 mol% of Mo, and that such a borosilicate glass matrix could only accommodate 1 mol% of Mo without phosphate doping. The effectiveness of phosphorus may be correlated with the Na content in borosilicate glass, and a high Na content borosilicate glass matrix requires more P doping to accommodate Mo. In addition, incorporating large amounts of P can compromise the aqueous durability of the glass matrix. Full article
(This article belongs to the Special Issue Glassy Materials: From Preparation to Application)
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13 pages, 4096 KiB  
Article
Inversion Method of the Young’s Modulus Field and Poisson’s Ratio Field for Rock and Its Test Application
by Yanchun Yin, Guangyan Liu, Tongbin Zhao, Qinwei Ma, Lu Wang and Yubao Zhang
Materials 2022, 15(15), 5463; https://doi.org/10.3390/ma15155463 - 08 Aug 2022
Cited by 2 | Viewed by 1469
Abstract
As one typical heterogeneous material, the heterogeneity of rock micro parameters has an important effect on its macro mechanical behavior. The study of the heterogeneity of micro parameters is more important to reveal the root cause of deformation and failure. However, as a [...] Read more.
As one typical heterogeneous material, the heterogeneity of rock micro parameters has an important effect on its macro mechanical behavior. The study of the heterogeneity of micro parameters is more important to reveal the root cause of deformation and failure. However, as a typical heterogeneous material, the current testing and inversion method is not suitable for micro parameters measurement for the rock. Aiming at obtaining the distribution of micro Young’s modulus and micro Poisson’s ratio of the rock, based on the digital image correlation method (DIC) and finite element method (FEM), this paper proposed a parameter field inversion method, namely the DF-PF inversion method. Its inversion accuracy is verified using numerical simulation and laboratory uniaxial compression test. Considering the influences of heterogeneity, stress state and dimension difference, the average inversion error of Young’s modulus field and Poisson’s ratio field are below 10%, and the proportion of elements with an error of less than 15% accounts for more than 86% in the whole specimen model. Compared with the conventional measuring method, the error of macro Young’s modulus and macro Poisson’s ratio calculated by the DF-PF inversion method is less than 2.8% and 9.07%, respectively. Based on the statistical analysis of Young’s modulus field and Poisson’s ratio field, the parameter homogeneity and quantitative function relation between the micro parameter and the principal strain can also be obtained in laboratory tests. The DF-PF inversion method provides a new effective method of testing Young’s modulus field and Poisson’s ratio field of the rocks under complex stress states. Full article
(This article belongs to the Special Issue Microstructure, Characterization and Mechanical Properties of Coal and Coal-Like Materials)
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16 pages, 9075 KiB  
Article
Investigating the Effect of Fly Ash Addition on the Metallurgical and Mechanical Behavior of Al-Si-Mg-Cu Alloy for Engine Cylinder Head Application
by Karthik Venkitraman Shankar, Jan Jezierski, Vaira Vignesh Ramalingam, Devaprasad Padmakumar, Midun Raj Leena, Amal, Gokul Reghunath and Rakesh Krishnan
Materials 2022, 15(15), 5462; https://doi.org/10.3390/ma15155462 - 08 Aug 2022
Cited by 9 | Viewed by 1816
Abstract
The authors researched the physical, metallurgical, and mechanical characteristics of A354 alloy (Al-Si-Mg-Cu) reinforced with 5, 10, and 15 wt% of fly ash metal matrix composites. A baseline alloy and three composites were fabricated by a liquid metallurgy route and poured into a [...] Read more.
The authors researched the physical, metallurgical, and mechanical characteristics of A354 alloy (Al-Si-Mg-Cu) reinforced with 5, 10, and 15 wt% of fly ash metal matrix composites. A baseline alloy and three composites were fabricated by a liquid metallurgy route and poured into a permanent mold to obtain cast rods of dimension Φ32 mm × 156 mm. The metallurgical characterization of the developed alloy and metal matrix composites was conducted using energy-dispersive spectroscopy (EDS), field-emission scanning electron microscopy (FESEM), and X-ray diffraction. All the developed composites showed a pore-free nature, but only A354 alloy reinforced with 5 wt% of fly ash (AF5) possessed a homogeneous distribution and perfect bonding of the fly ash with the A354 matrix. Therefore, transmission electron microscopy (TEM) analysis was performed on the sample AF5. All developed alloys and metal matrix composites were subjected to hardness and mechanical property tests. It was observed that the AF5 sample had 170 ± 5.6 HV and tensile strength of 216 ± 2.3 MPa, 18.8% and 24.8% higher than the A354 matrix, but the ductility (6.5 ± 0.43%) was reduced by 23% from the baseline alloy. Finally, the fractography analysis was conducted on all the samples using FESEM to analyze the fracture mode. The fabricated 5 wt% fly ash-based metal matrix composite showed better mechanical performance than other samples. Hence, sample AF5 is suggested for manufacturing components in automotive and structural parts. Full article
(This article belongs to the Topic Metal Matrix Composites: Recent Advancements)
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20 pages, 4197 KiB  
Article
A Coupled CFD-DEM Study on the Effect of Basset Force Aimed at the Motion of a Single Bubble
by Huiting Chen, Weitian Ding, Han Wei, Henrik Saxén and Yaowei Yu
Materials 2022, 15(15), 5461; https://doi.org/10.3390/ma15155461 - 08 Aug 2022
Cited by 7 | Viewed by 1601
Abstract
The physical meaning of Basset force is first studied via polynomial approximation and the Fourier series representation method. After compiling the Basset force into the coupling interface with Visual C, a dynamic mathematical model is set up to describe the upward motion behavior [...] Read more.
The physical meaning of Basset force is first studied via polynomial approximation and the Fourier series representation method. After compiling the Basset force into the coupling interface with Visual C, a dynamic mathematical model is set up to describe the upward motion behavior of a single bubble by adopting the CFD-DEM method. Afterwards, the coupling interface with Basset force proposed in this study is verified experimentally and shows very good agreements. The initial velocity, releasing depth, bubble size, density ratio and viscosity ratio are studied qualitatively due to their great importance to Basset force. The ratio of Basset force to the sum of Basset force and drag force and to buoyancy, F→Ba/(F→D+F→Ba) and |F→Ba/F→B|, are employed to quantify the contribution of Basset force quantitatively. In addition, some instructive outlooks and recommendations on a further development of appropriate and justifiable use of Basset force are highlighted at last. Full article
(This article belongs to the Special Issue Numerical Simulations in Metal Refining Process)
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17 pages, 47990 KiB  
Article
Microstructures and Properties of Al-Mg Alloys Manufactured by WAAM-CMT
by Yan Liu, Zhaozhen Liu, Guishen Zhou, Chunlin He and Jun Zhang
Materials 2022, 15(15), 5460; https://doi.org/10.3390/ma15155460 - 08 Aug 2022
Cited by 8 | Viewed by 1899
Abstract
A wire arc additive manufacturing system, based on cold metal transfer technology, was utilized to manufacture the Al-Mg alloy walls. ER5556 wire was used as the filler metal to deposit Al-Mg alloys layer by layer. Based on the orthogonal experiments, the process parameters [...] Read more.
A wire arc additive manufacturing system, based on cold metal transfer technology, was utilized to manufacture the Al-Mg alloy walls. ER5556 wire was used as the filler metal to deposit Al-Mg alloys layer by layer. Based on the orthogonal experiments, the process parameters of the welding current, welding speed and gas flow, as well as interlayer residence time, were adjusted to investigate the microstructure, phase composition and crystal orientation as well as material properties of Al-Mg alloyed additive. The results show that the grain size of Al-Mg alloyed additive becomes smaller with the decrease of welding current or increased welding speed. It is easier to obtain the additive parts with better grain uniformity with the increase of gas flow or interlayer residence time. The phase composition of Al-Mg alloyed additive consists of α-Al matrix and γ (Al12Mg17) phase. The eutectic reaction occurs during the additive manufacturing process, and the liquefying film is formed on the α-Al matrix and coated on the γ phase surface. The crystal grows preferentially along the <111> and <101> orientations. When the welding current is 90 A, the welding speed is 700 mm/min, the gas flow is 22.5 L/min and the interlayer residence time is 5 min, the Al-Mg alloy additive obtains the highest tensile strength. Under the optimal process parameters, the average grain size of Al-Mg alloyed additive is 25 μm, the transverse tensile strength reaches 382 MPa, the impact absorption energy is 26 J, and the corrosion current density is 3.485 × 10−6 A·cm−2. Both tensile and impact fracture modes of Al-Mg alloyed additive are ductile fractures. From the current view, the Al-Mg alloys manufactured by WAAM-CMT have a better performance than those produced by the traditional casting process. Full article
(This article belongs to the Special Issue Research Progress in High-Performance Magnesium Alloy and Its Applications)
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30 pages, 10383 KiB  
Review
Research on the Manufacturing Process and Heat Transfer Performance of Ultra-Thin Heat Pipes: A Review
by Liuyang Duan, Hang Li, Jinguang Du, Kun Liu and Wenbin He
Materials 2022, 15(15), 5459; https://doi.org/10.3390/ma15155459 - 08 Aug 2022
Cited by 4 | Viewed by 3750
Abstract
This paper reviews the manufacturing process of ultra-thin heat pipes and the latest process technologies in detail, focusing on the progress of the shape, structure, and heat transfer mechanism of the wick. The effects of the filling rate and tilt angle on the [...] Read more.
This paper reviews the manufacturing process of ultra-thin heat pipes and the latest process technologies in detail, focusing on the progress of the shape, structure, and heat transfer mechanism of the wick. The effects of the filling rate and tilt angle on the heat transfer performance of the ultra-thin heat pipe, as well as the material selection of ultra-thin heat pipes, is sorted out, and the surface modification technology is analyzed. Besides, the optimal design based on heat pipes is discussed. Spiral woven mesh wick and multi-size composite wick have significant advantages in the field of ultra-thin heat pipe heat transfer, and comprehensive surface modification technology has huge potential. Finally, an outlook on future scientific research in the field of ultra-thin heat pipes is proposed. Full article
(This article belongs to the Special Issue Porous Ceramics, Glasses and Composites)
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24 pages, 7427 KiB  
Article
A Comprehensive Study on the Rejuvenation Efficiency of Compound Rejuvenators for the Characterization of the Bituminous Binder, Mortar, and Mixture
by Mingliang Li, Shisong Ren, Xueyan Liu, Zhe Wu, Haopeng Zhang, Weiyu Fan, Peng Lin and Jian Xu
Materials 2022, 15(15), 5458; https://doi.org/10.3390/ma15155458 - 08 Aug 2022
Cited by 5 | Viewed by 1456
Abstract
This study aims to comprehensively investigate the rejuvenation efficiency of various self-developed compound rejuvenators on the physical, mechanical, and aging properties of aged bitumen, asphalt mortar, and mixture. The results revealed that the restoration capacity of vacuum distilled-oil rejuvenators on high-and-low temperature performance-grade [...] Read more.
This study aims to comprehensively investigate the rejuvenation efficiency of various self-developed compound rejuvenators on the physical, mechanical, and aging properties of aged bitumen, asphalt mortar, and mixture. The results revealed that the restoration capacity of vacuum distilled-oil rejuvenators on high-and-low temperature performance-grade of aged bitumen is more significant. In contrast, an aromatic-oil based rejuvenator is good at enhancing low-temperature grade and aging resistance. Moreover, the temperature and time of the curing conditions for mixing recycling of asphalt mixture were optimized as 150 °C and 120 min. Furthermore, the sufficient anti-rutting, structural stability, and moisture resistance of recycled asphalt mixture affirmed the rejuvenation efficiency of compound rejuvenators. Full article
(This article belongs to the Special Issue Long-Life and Circular Pavement Materials)
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51 pages, 6077 KiB  
Review
Additive Manufacturing of Biomaterials—Design Principles and Their Implementation
by Mohammad J. Mirzaali, Vahid Moosabeiki, Seyed Mohammad Rajaai, Jie Zhou and Amir A. Zadpoor
Materials 2022, 15(15), 5457; https://doi.org/10.3390/ma15155457 - 08 Aug 2022
Cited by 29 | Viewed by 5908
Abstract
Additive manufacturing (AM, also known as 3D printing) is an advanced manufacturing technique that has enabled progress in the design and fabrication of customised or patient-specific (meta-)biomaterials and biomedical devices (e.g., implants, prosthetics, and orthotics) with complex internal microstructures and tuneable properties. In [...] Read more.
Additive manufacturing (AM, also known as 3D printing) is an advanced manufacturing technique that has enabled progress in the design and fabrication of customised or patient-specific (meta-)biomaterials and biomedical devices (e.g., implants, prosthetics, and orthotics) with complex internal microstructures and tuneable properties. In the past few decades, several design guidelines have been proposed for creating porous lattice structures, particularly for biomedical applications. Meanwhile, the capabilities of AM to fabricate a wide range of biomaterials, including metals and their alloys, polymers, and ceramics, have been exploited, offering unprecedented benefits to medical professionals and patients alike. In this review article, we provide an overview of the design principles that have been developed and used for the AM of biomaterials as well as those dealing with three major categories of biomaterials, i.e., metals (and their alloys), polymers, and ceramics. The design strategies can be categorised as: library-based design, topology optimisation, bio-inspired design, and meta-biomaterials. Recent developments related to the biomedical applications and fabrication methods of AM aimed at enhancing the quality of final 3D-printed biomaterials and improving their physical, mechanical, and biological characteristics are also highlighted. Finally, examples of 3D-printed biomaterials with tuned properties and functionalities are presented. Full article
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14 pages, 5710 KiB  
Article
Experimental Investigation on Mechanical Properties of Geocell Strips at Low Temperature
by Qiyu Bai, Guofeng He, Yong Wang and Jie Liu
Materials 2022, 15(15), 5456; https://doi.org/10.3390/ma15155456 - 08 Aug 2022
Cited by 6 | Viewed by 1585
Abstract
Geocell is widely used in the treatment of poor roadbed, which can restrain soil laterally and improve the stability of soil. In cold area engineering, a change in temperature can influence the mechanical properties of geocell of different materials. To study the mechanical [...] Read more.
Geocell is widely used in the treatment of poor roadbed, which can restrain soil laterally and improve the stability of soil. In cold area engineering, a change in temperature can influence the mechanical properties of geocell of different materials. To study the mechanical response of geocell at low temperatures, three types of geocell strips commonly used in engineering, namely the polyethylene (HDPE), polypropylene (PP), and polyester (PET), were studied via the uniaxial tensile test at the ambient temperatures of −5 °C, −20 °C, and −35 °C, respectively. Meanwhile, the tensile strength, fracture mode, and temperature sensitivity of geocell specimens were compared. It is concluded that: (1) at low temperatures, the tensile strengths of HDPE and PET geocell strips are significantly improved, while that of the PP geocell strip is less sensitive to the temperature. (2) The PP geocell is subject to a brittle failure at all ambient temperatures. The PET geocell strip experiences a hard-ductile failure at normal temperatures of −5 °C and −20 °C. While in the tensile test at −35 °C, it is prone to brittle failure and hard-ductile failure. The HDPE geocell strip suffers from ductile failure at all ambient temperatures. (3) At low temperatures, overall, the tensile properties of the PET geocell strip is better than those of the PP and HDPE geocell strips. Full article
(This article belongs to the Section Construction and Building Materials)
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14 pages, 4547 KiB  
Article
Microwave Absorption Properties of Carbon Black-Carbonyl Iron/Polylactic Acid Composite Filament for Fused Deposition Modeling
by Fei Wang, Qianfeng Zhou, Zhe Zhang, Yonghua Gu, Jiliang Zhang and Kaiyong Jiang
Materials 2022, 15(15), 5455; https://doi.org/10.3390/ma15155455 - 08 Aug 2022
Cited by 12 | Viewed by 1799
Abstract
A single microwave absorbent and simple coating structure cannot meet the increasing requirements for broadband and strong absorption. Three-dimensional printing is an effective way to prepare multi-component complex structure metamaterial absorbers, and the key is to prepare raw materials with excellent absorption properties, [...] Read more.
A single microwave absorbent and simple coating structure cannot meet the increasing requirements for broadband and strong absorption. Three-dimensional printing is an effective way to prepare multi-component complex structure metamaterial absorbers, and the key is to prepare raw materials with excellent absorption properties, suitable for 3D printing. In this paper, CB-CIP/PLA composite filament was prepared via a high-energy mixer and twin-screw extruder by compounding the dielectric loss material carbon black (CB) and the magnetic loss material carbonyl iron powder (CIP) with polylactic acid (PLA) as the matrix. The coaxial ring test piece was printed by FDM technology, and the microstructure of the composites was observed and analyzed by SEM. Meanwhile, the electromagnetic parameters of the composites were examined by a vector network analyzer, mainly studying the influence of the CB and CIP content and thickness on the microwave absorbing properties of the composite material. The results show that when the CB content is 20% and the CIP content is 30%, the CB-CIP/PLA composite has excellent microwave absorption and broad bandwidth. When the matching thickness is 1.6 mm, the minimum reflection loss (RL) reaches −51.10 dB; when the thickness is 1.7 mm, the effective absorption bandwidth (RL < −10 dB) is 5.04 GHz (12.96–18 GHz), nearly covering the whole Ku band. This work provides an efficient formulation and process to prepare an absorbing composite filament for FDM. Full article
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18 pages, 15960 KiB  
Article
Joining Processes for Fibre-Reinforced Thermoplastics: Phenomena and Characterisation
by Juliane Troschitz, Benjamin Gröger, Veit Würfel, Robert Kupfer and Maik Gude
Materials 2022, 15(15), 5454; https://doi.org/10.3390/ma15155454 - 08 Aug 2022
Cited by 9 | Viewed by 1687 | Correction
Abstract
Thermoplastic composites (TPCs) are predestined for use in lightweight structures, especially for high-volume applications. In many cases, joining is a key factor for the successful application of TPCs in multi-material systems. Many joining processes for this material group are based on warm forming [...] Read more.
Thermoplastic composites (TPCs) are predestined for use in lightweight structures, especially for high-volume applications. In many cases, joining is a key factor for the successful application of TPCs in multi-material systems. Many joining processes for this material group are based on warm forming the joining zone. This results in a change of the local material structure characterised by modified fibre paths, as well as varying fibre contents, which significantly influences the load-bearing behaviour. During the forming process, many different phenomena occur simultaneously at different scales. In this paper, the deformation modes and flow mechanisms of TPCs during forming described in the literature are first analysed. Based on this, three different joining processes are investigated: embedding of inserts, moulding of contour joints, and hotclinching. In order to identify the phenomena occurring in each process and to describe the characteristic resulting material structure in the joining zones, micrographs as well as computed tomography (CT) analyses are performed for both individual process stages and final joining zones. Full article
(This article belongs to the Special Issue Advances in Manufacturing Technology of Metal/Composite Hybrid Structures)
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16 pages, 8896 KiB  
Article
Aluminide Diffusion Coatings on IN 718 by Pack Cementation
by Mihai Ovidiu Cojocaru, Mihai Branzei and Leontin Nicolae Druga
Materials 2022, 15(15), 5453; https://doi.org/10.3390/ma15155453 - 08 Aug 2022
Cited by 3 | Viewed by 1576
Abstract
This paper addressed the issues of both direct and indirect synthesis of Ni aluminides by pack cementation (pure Ni and IN 718 superalloy). On the Al-Ni diffusion twosome under pressure, at temperatures below and above the Al melting temperature, the appearance and evolution [...] Read more.
This paper addressed the issues of both direct and indirect synthesis of Ni aluminides by pack cementation (pure Ni and IN 718 superalloy). On the Al-Ni diffusion twosome under pressure, at temperatures below and above the Al melting temperature, the appearance and evolution of diffusion porosity because of the Kirkendall–Frenkel effect manifestation was highlighted. It has been confirmed that, as the temperature rises above the Al melting temperature, the porosity decreases. Nickel-based superalloys, and in particular IN 718, significantly increase their performance by increasing the aluminides proportion in the top diffusion coating. This is made possible by changing the value of the Al and Ni weight percentage ratio in this area (noted as Al/Ni). In the case of the diffusion twosome between IN 718 and pack aluminizing mixtures, having in their composition as active components Al powder, Ferroaluminum (FeAl40) or mixtures of Al and Fe powders, at processing temperatures above the Al melting temperature, by modifying the active component of the mixture, substantial changes in the Al/Ni values were observed, as well as in the maximum %Al in the diffusion coating and of its thickness. It was found that, when switching from Al to FeAl40 or powder mixture (Al + Fe), the Al/Ni value changes between 3.43 and 1.01, from initial subunit values. The experiments confirmed that the highest %Al in the top aluminized diffusion coating, for IN 718, was obtained if the powder mixture contained 66.34 wt.% Al. Full article
(This article belongs to the Special Issue Surface Processing Technology for High-Temperature Resistant Materials)
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20 pages, 12025 KiB  
Article
Mesoscale Finite Element Modeling of Mortar under Sulfate Attack
by Zhongzheng Guan, Peng Wang, Yue Li, Yong Li, Bo Hu and Yichao Wang
Materials 2022, 15(15), 5452; https://doi.org/10.3390/ma15155452 - 08 Aug 2022
Viewed by 1169
Abstract
In this paper, a 2D mesoscale finite element (FE) numerical model of mortar, considering the influence of the ITZ, was proposed to evaluate the corrosion of mortar in sodium sulfate. On the mesoscale, the corroded mortar was regarded as a three-phase composite material [...] Read more.
In this paper, a 2D mesoscale finite element (FE) numerical model of mortar, considering the influence of the ITZ, was proposed to evaluate the corrosion of mortar in sodium sulfate. On the mesoscale, the corroded mortar was regarded as a three-phase composite material composed of sand, cement paste, and an interface transition zone (ITZ). Firstly, the volume fractions and mechanical parameters (elastic modulus, Poisson’s ratio, and strength) of the mesoscale phases were obtained. Then, the cement paste and the ITZ were combined to form an equivalent matrix by homogenization methods, and the calibrated constitutive relations of the equivalent matrix were established. Subsequently, a two-dimensional (2D) random circular aggregate (RCA) model and a 2D random polygonal aggregate (RPA) model of corroded mortar were established using the random aggregate model. The failure process of corroded mortar specimens under uniaxial compression was simulated by the mesoscale FE numerical model. Comparing the simulation results with the measured stress–strain curves of the uniaxial compression test, it was found that the simulation results of the 2D RP model were closer to the experimental results than those of the 2D RC model. Meanwhile, the numerical simulation results were in good agreement with the experimental results, and the error values of peak stress between the simulation results and the measured results were within 7%, which showed that the 2D mesoscale FE model could accurately predict the results of a uniaxial compression test of a mortar specimen under sulfate attack. Full article
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33 pages, 15218 KiB  
Article
Experimental Investigation and Performance Optimization during Machining of Hastelloy C-276 Using Green Lubricants
by Gurpreet Singh, Vivek Aggarwal, Sehijpal Singh, Balkar Singh, Shubham Sharma, Jujhar Singh, Changhe Li, R.A. Ilyas and Abdullah Mohamed
Materials 2022, 15(15), 5451; https://doi.org/10.3390/ma15155451 - 08 Aug 2022
Cited by 15 | Viewed by 2045
Abstract
Smart manufacturing is the demand of industry 4.0, in which the mass production of difficult-to-cut materials is of great concern to fulfil the goal of sustainable machining. Presently, the machining of superalloy is of upmost interest because of its wide application. However, the [...] Read more.
Smart manufacturing is the demand of industry 4.0, in which the mass production of difficult-to-cut materials is of great concern to fulfil the goal of sustainable machining. Presently, the machining of superalloy is of upmost interest because of its wide application. However, the limited data on the turning of Hastelloy C-276 highlights its challenges during processing. Hence, the machining performance of superalloy considering surface quality, thermal aspects and chip reduction coefficient was examined with minimum quantity lubrication of several oils to address the sustainable development goal (SDG-12). The output responses were optimized through response surface methodology along with analysis of variance. The research exhibited that the output responses were dominated by cutting speed and feed rate having a percentage benefaction of 24.26% and 60%, respectively, whilst the depth of cut and lubricant type have an influence of 10–12%. No major difference in temperature range was reported during the different lubrication conditions. However, a substantial variation in surface roughness and the chip reduction coefficient was revealed. The percentage error evaluated in surface roughness, temperature and chip reduction coefficient was less than 5%, along with an overall desirability of 0.88, describing the usefulness of the model used. The SEM micrograph indicated a loss of coating, nose and flank wear during all lubrication conditions. Lastly, incorporating a circular economy has reduced the economic, ecological and environmental burden. Full article
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56 pages, 7034 KiB  
Review
Color Conversion Light-Emitting Diodes Based on Carbon Dots: A Review
by Danilo Trapani, Roberto Macaluso, Isodiana Crupi and Mauro Mosca
Materials 2022, 15(15), 5450; https://doi.org/10.3390/ma15155450 - 08 Aug 2022
Cited by 8 | Viewed by 2865
Abstract
This paper reviews the state-of-the-art technologies, characterizations, materials (precursors and encapsulants), and challenges concerning multicolor and white light-emitting diodes (LEDs) based on carbon dots (CDs) as color converters. Herein, CDs are exploited to achieve emission in LEDs at wavelengths longer than the pump [...] Read more.
This paper reviews the state-of-the-art technologies, characterizations, materials (precursors and encapsulants), and challenges concerning multicolor and white light-emitting diodes (LEDs) based on carbon dots (CDs) as color converters. Herein, CDs are exploited to achieve emission in LEDs at wavelengths longer than the pump wavelength. White LEDs are typically obtained by pumping broad band visible-emitting CDs by an UV LED, or yellow–green-emitting CDs by a blue LED. The most important methods used to produce CDs, top-down and bottom-up, are described in detail, together with the process that allows one to embed the synthetized CDs on the surface of the pumping LEDs. Experimental results show that CDs are very promising ecofriendly candidates with the potential to replace phosphors in traditional color conversion LEDs. The future for these devices is bright, but several goals must still be achieved to reach full maturity. Full article
(This article belongs to the Special Issue Organic Materials for Electronic and Optoelectronic Applications)
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7 pages, 244 KiB  
Article
The Effect of a 10-MDP-Based Dentin Adhesive as Alternative for Bonding to Implant Abutment Materials
by Paula C. K. Carvalho, Cláudia C M S Almeida, Rodrigo O. A. Souza and Rubens Nisie Tango
Materials 2022, 15(15), 5449; https://doi.org/10.3390/ma15155449 - 08 Aug 2022
Cited by 4 | Viewed by 1366
Abstract
Bonding to different dental restorative materials is challenging. This study aimed to evaluate the effect of a 10-MDP-based dentin adhesive on the shear bond strength (SBS) of self-adhesive resin cement (RC) to implant abutment materials. One hundred and twenty specimens were obtained from [...] Read more.
Bonding to different dental restorative materials is challenging. This study aimed to evaluate the effect of a 10-MDP-based dentin adhesive on the shear bond strength (SBS) of self-adhesive resin cement (RC) to implant abutment materials. One hundred and twenty specimens were obtained from zirconia (ZO), cobalt-chromium alloy (CoCr), and commercially pure titanium (Ti), which were treated as follows (n = 10): control group—non-treated (CG), 10-MDP-based dentin adhesive (SB), light-cured SB (SB-LC), and zirconia primer (ZP). Blocks of RC were buildup and, after 24 h, were tested for bond strength. Data of SBS (MPa) were submitted to two-way ANOVA and Tukey test (α = 0.05). There was no difference in SBS among materials for CG and ZP, higher SBS were recorded for Ti SB and Ti SB-LC compared to ZO upon the same surface treatments. For the comparisons among treatments, SB-LC showed the highest SBS for CoCr. For ZO and Ti, higher SBS were recorded with SB and SB-LC. No cohesive failures were observed. It was concluded that the surface treatment with 10-MDP-based materials increased the bond strength of the resin cement to abutment materials, which showed to be material dependent. Full article
(This article belongs to the Special Issue Polymeric Materials for Oral and Maxillofacial Reconstructive Treatment)
10 pages, 11711 KiB  
Article
Analysis of Electromagnetic Shielding Properties of a Material Developed Based on Silver-Coated Copper Core-Shell Spraying
by Yu-Jae Jeon, Jong-Hwan Yun and Min-Soo Kang
Materials 2022, 15(15), 5448; https://doi.org/10.3390/ma15155448 - 08 Aug 2022
Cited by 6 | Viewed by 1594
Abstract
This study proposes an electromagnetic shielding material sprayed with silver-coated copper powder (core-shell powder). The shielding properties of the material are analyzed in details section. Cross-sectional observation and sheet resistance measurement were used to determine the thickness and electrical conductivity of the electromagnetic [...] Read more.
This study proposes an electromagnetic shielding material sprayed with silver-coated copper powder (core-shell powder). The shielding properties of the material are analyzed in details section. Cross-sectional observation and sheet resistance measurement were used to determine the thickness and electrical conductivity of the electromagnetic shielding layer, which was generated by spray-coating; this aided in confirming the uniformity of the coating film. The results indicate that the electromagnetic interference shielding effectiveness increases when the silver-coated copper paste (core-shell paste) is used as the coating material rather than the conventional aluminum base. The proposed material can be used in various frequency ranges owing to the excellent shielding effectiveness of the core-shell paste used in this study. Further investigations on the optimized spray-coating type of electromagnetic shielding material are required based on the composition of the core-shell paste and the thickness of the coating film. Full article
(This article belongs to the Special Issue Recent Advances in Electromagnetic Interference Shielding Materials)
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20 pages, 5206 KiB  
Article
Application of a New Alloy and Post Processing Procedures for Laser Cladding Repairs on Hypereutectoid Rail Components
by Olivia Kendall, Panahsadat Fasihi, Ralph Abrahams, Anna Paradowska, Mark Reid, Quan Lai, Cong Qiu, Peter Mutton, Mehdi Soodi and Wenyi Yan
Materials 2022, 15(15), 5447; https://doi.org/10.3390/ma15155447 - 08 Aug 2022
Cited by 7 | Viewed by 2142
Abstract
The development of a laser cladding repair strategy is critical for the continued growth of heavy-haul railway networks. Premium hypereutectoid rails have undergone laser cladding using a new martensitic stainless-steel alloy, 415SS, developed for high carbon rails after standard cladding metals were found [...] Read more.
The development of a laser cladding repair strategy is critical for the continued growth of heavy-haul railway networks. Premium hypereutectoid rails have undergone laser cladding using a new martensitic stainless-steel alloy, 415SS, developed for high carbon rails after standard cladding metals were found to be incompatible. Non-destructive neutron diffraction techniques were used to measure the residual stress in different layers generated across a dissimilar metal joint during laser cladding. The internal stress distribution across the cladding, heat-affected zone (HAZ), and substrate was measured in the untempered rail, after 350 °C and 540 °C heat treatment procedures and two surface grinding operations. The martensitic 415SS depositions produce compressive stress in the cladding, regardless of tempering procedures, which may inhibit fatigue crack propagation whilst grinding operations locally relive surface stress. Balancing tensile stresses were recorded below the fusion boundary in the HAZ due to thermal gradients altering the microstructure. The combination of 540 °C tempering and 0.5 mm surface layer removal produced a desirable combination of compression in the cladding deposition with significantly reduced tensile stresses in the HAZ. A comparison with the current literature shows that this alloy achieves a unique combination of desirable hardness, low tensile stress, and compression in the cladding layer. Data obtained during strain scanning has been used to determine the location of microstructural changes at the fusion boundary and HAZ through correlation of the stress, strain, full width at half maximum (FWHM), and intensity profiles. Therefore, neutron diffraction can be used for both the accurate measurement of internal residual stress and to obtain microstructural information of a metallurgical join non-destructively. Full article
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10 pages, 4608 KiB  
Article
Aluminum Perlite Syntactic Foams
by György Thalmaier, Niculina Argentina Sechel, Alexandra Csapai, Catalin Ovidiu Popa, Gabriel Batin, Andras Gábora, Tamas Mankovits and Ioan Vida-Simiti
Materials 2022, 15(15), 5446; https://doi.org/10.3390/ma15155446 - 08 Aug 2022
Cited by 3 | Viewed by 1373
Abstract
This paper presents the usage of spark plasma sintering (SPS) as a method to obtain aluminum-expanded perlite syntactic foams with high porosity. In the test samples, fine aluminum powder with flaky shape particles was used as matrix material and natural, inorganic, granular, expanded [...] Read more.
This paper presents the usage of spark plasma sintering (SPS) as a method to obtain aluminum-expanded perlite syntactic foams with high porosity. In the test samples, fine aluminum powder with flaky shape particles was used as matrix material and natural, inorganic, granular, expanded perlite was used as a space holder to ensure high porosity (35–57%) and uniform structure. SPS was used to consolidate the specimens. The structures were characterized by scanning electron microscopy and compression tests. Energy absorption (W~7.49 MJ/m3) and energy absorption efficiency (EW < 90%) were also determined. Full article
(This article belongs to the Special Issue State-of-the-Art Materials Science and Engineering Scientific Research—Romanian Technical Science Academy)
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9 pages, 2930 KiB  
Article
Effects of Preparation Methods on the Microstructure and Mechanical Properties of Graphene-Reinforced Alumina Matrix Composites
by Danxia Zhang, Xiaoqian Wu, Bi Jia, Hanmei Jiang, Yin Liu, Rong Wang, Qian Yang, Huiming Wu and Chunyan Wu
Materials 2022, 15(15), 5445; https://doi.org/10.3390/ma15155445 - 08 Aug 2022
Cited by 2 | Viewed by 1369
Abstract
Recent years have witnessed a growing research interest in graphene-reinforced alumina matrix composites (Al2O3-G). In this paper, to better achieve the dispersion of graphene in composites, a ball milling method for adding raw materials step by step, called stepwise [...] Read more.
Recent years have witnessed a growing research interest in graphene-reinforced alumina matrix composites (Al2O3-G). In this paper, to better achieve the dispersion of graphene in composites, a ball milling method for adding raw materials step by step, called stepwise feeding ball milling, was proposed. The Al2O3-1.0 wt % graphene composites were prepared by this stepwise feeding ball milling and hot pressing. Then, the effects of sintering temperature and sintering pressure on the microstructure and mechanical properties of composites were studied. Results showed that the bending strength, fracture toughness and Vickers hardness of composites increased firstly and then decreased with increasing sintering temperature. The mechanical properties of composites were all at their maximum with the sintering temperature of 1550 °C. For example, the bending strength of composites reached 754.20 MPa, which was much bigger than 478.03 MPa at 1500 °C and 364.01 MPa at 1600 °C. Analysis suggested that the strength of composites was mainly related to the grain size, microflaw size and porosity. Full article
(This article belongs to the Special Issue Development and Application of High-Temperature Ceramics)
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18 pages, 4341 KiB  
Article
A Biological Study of Composites Based on the Blends of Nanohydroxyapatite, Silk Fibroin and Chitosan
by Anna Tuwalska, Alina Sionkowska, Amadeusz Bryła, Grzegorz Tylko, Anna Maria Osyczka, Michele Laus and Lucy Vojtová
Materials 2022, 15(15), 5444; https://doi.org/10.3390/ma15155444 - 08 Aug 2022
Cited by 3 | Viewed by 1657
Abstract
In this work, the biological properties of three-dimensional scaffolds based on a blend of nanohydroxyapatite (nHA), silk fibroin (SF), and chitosan (CTS), were prepared using a lyophilization technique with various weight ratios: 10:45:45, 15:15:70, 15:70:15, 20:40:40, 40:30:30, and 70:15:15 nHA:SF:CTS, respectively. The basic [...] Read more.
In this work, the biological properties of three-dimensional scaffolds based on a blend of nanohydroxyapatite (nHA), silk fibroin (SF), and chitosan (CTS), were prepared using a lyophilization technique with various weight ratios: 10:45:45, 15:15:70, 15:70:15, 20:40:40, 40:30:30, and 70:15:15 nHA:SF:CTS, respectively. The basic 3D scaffolds were obtained from 5% (w/w) chitosan and 5% silk fibroin solutions and then nHA was added. The morphology and physicochemical properties of scaffolds were studied and compared. A biological test was performed to study the growth and osteogenic differentiation of human bone marrow mesenchymal stem cells (hMSCs). It was found that the addition of chitosan increases the resistance properties and extends the degradation time of materials. In vitro studies with human mesenchymal stem cells found a high degree of biotolerance for the materials produced, especially for the 20:40:40 and 15:70:15 (nHa:SF:CTS) ratios. The presence of silk fibroin and the elongated shape of the pores positively influenced the differentiation of cells into osteogenic cells. By taking advantage of the differentiation/proliferation cues offered by individual components, the composites based on the nanohydroxyapatite, silk fibroin, and chitosan scaffold may be suitable for bone tissue engineering, and possibly offer an alternative to the widespread use of collagen materials. Full article
(This article belongs to the Special Issue Feature Paper in the Section 'Polymeric Materials')
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12 pages, 5013 KiB  
Article
Tuning the Surface Characteristics and Mechanical Properties of Y2O3 Coatings on a Graphene Matrix via Laser Micro Melting
by Hao Liu, Ping-hu Chen, Yong Chen, Wen-xing Wu, Sheng Li and Chang-jun Qiu
Materials 2022, 15(15), 5443; https://doi.org/10.3390/ma15155443 - 08 Aug 2022
Cited by 1 | Viewed by 1373
Abstract
The effects of laser parameters on the microstructure and properties of plasma-sprayed yttrium oxide coating on the graphite matrix were investigated. Tensile strength, porosity, roughness, and scratch meter tests were carried out to evaluate the critical load and mechanical properties of the coating [...] Read more.
The effects of laser parameters on the microstructure and properties of plasma-sprayed yttrium oxide coating on the graphite matrix were investigated. Tensile strength, porosity, roughness, and scratch meter tests were carried out to evaluate the critical load and mechanical properties of the coating after spraying and laser micro-melting. When the porosity and surface roughness of the coating are minimum, the critical load of the coating is 7.85 N higher than that of the spraying surface. After laser micromelting, the crystal phase of Y2O3 coating surface does not change, the crystallinity is improved, and fine grain strengthening occurs. When the laser power density is 75 W/mm2, the scanning speed is 30 mm/s, and the defocusing distance is 40 mm, the film base bonding performance and wear resistance of the material reach the maximum value. The failure of Y2O3 coating is mainly due to the degradation of mechanical properties such as film base bonding strength, surface porosity, and surface roughness, which leads to the local collapse of the material. The coating after laser micro-melting only presents particle disintegration at the end of the scratch area. Full article
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11 pages, 1641 KiB  
Article
A Clinical Risk Assessment of a 3D-Printed Patient-Specific Scaffold by Failure Modes and Effects Analysis
by Ping Qi Lim, Sue Huey Lim, Maria Sherilyn, Tulio Fernandez-Medina, Sašo Ivanovski and Sepanta Hosseinpour
Materials 2022, 15(15), 5442; https://doi.org/10.3390/ma15155442 - 08 Aug 2022
Viewed by 1298
Abstract
This study aims to carry out a risk assessment to identify and rectify potential clinical risks of a 3D-printed patient-specific scaffold for large-volume alveolar bone regeneration. A survey was used to assess clinicians’ perceptions regarding the use of scaffolds in the treatment of [...] Read more.
This study aims to carry out a risk assessment to identify and rectify potential clinical risks of a 3D-printed patient-specific scaffold for large-volume alveolar bone regeneration. A survey was used to assess clinicians’ perceptions regarding the use of scaffolds in the treatment of alveolar defects and conduct a clinical risk assessment of the developed scaffold using the Failure Modes and Effects Analysis (FMEA) framework. The response rate was 69.4% with a total of 41 responses received. Two particular failure modes were identified as a high priority through the clinical risk assessment conducted. The highest mean Risk Priority Number was obtained by “failure of healing due to patient risk factors” (45.7 ± 27.7), followed by “insufficient soft tissue area” (37.8 ± 24.1). Despite the rapid developments, finding a scaffold that is both biodegradable and tailored to the patient’s specific defect in cases of large-volume bone regeneration is still challenging for clinicians. Our results indicate a positive perception of clinicians towards this novel scaffold. The FMEA clinical risk assessment has revealed two failure modes that should be prioritized for risk mitigation (safe clinical translation). These findings are important for the safe transition to in-human trials and subsequent clinical use. Full article
(This article belongs to the Special Issue Novel Dental Materials: Recent Developments, Advances, and Applications)
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14 pages, 9799 KiB  
Article
Effect of Yttrium on the Microstructure and Mechanical Properties of PH13-8Mo Stainless Steels Produced by Selective Laser Melting
by Chang-Jun Wang, Chang Liu, Meng-Xing Zhang, Lu Jiang, Yu Liu, Zhen-Bao Liu and Jian-Xiong Liang
Materials 2022, 15(15), 5441; https://doi.org/10.3390/ma15155441 - 08 Aug 2022
Viewed by 1555
Abstract
In the present work, PH13-8Mo stainless steel parts without yttrium and with yttrium (Y) were manufactured by selective laser melting (SLM). The microstructure, phase composition and grain orientation of the stainless steels parts with Y and without Y were characterized by scanning electron [...] Read more.
In the present work, PH13-8Mo stainless steel parts without yttrium and with yttrium (Y) were manufactured by selective laser melting (SLM). The microstructure, phase composition and grain orientation of the stainless steels parts with Y and without Y were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), electron-backscatter diffraction (EBSD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The characterization results revealed that the addition of Y clearly refined the grain size of the PH13-8Mo steel formed part, resulting in more equiaxed massive grains and in a less anisotropic microstructure. PH13-8Mo stainless steel formed parts were mainly composed of martensite and retained austenite. The addition of Y could significantly increase the content of retained austenite and also generate nano-sized precipitates containing Y. The mechanical test results showed that both strength and toughness of the shaped parts containing Y were improved synergistically. The yield strength reached 1443 MPa, the elongation was 12.2%, and the room temperature impact energy reached 124.25 J/cm2. The strengthening and toughening by Y of the formed parts were mainly attributed to grain refinement, higher volume fraction of the retained austenite and the formation of nano-sized precipitates containing Y. Full article
(This article belongs to the Special Issue Advanced Structural Steels and Alloys)
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12 pages, 3335 KiB  
Article
Evaluation of a Method to Determine Wear Resistance of Class I Tooth Restorations during Cyclic Loading
by Philipp Messer-Hannemann, Mariam Samadi, Henrik Böttcher, Sebastian Duy, Daniela Duy, Niclas Albrecht, Falk Schwendicke and Susanne Effenberger
Materials 2022, 15(15), 5440; https://doi.org/10.3390/ma15155440 - 08 Aug 2022
Cited by 1 | Viewed by 1585
Abstract
The aim of this study was the development of a test regime to determine the wear resistance and predict the clinical performance of conventional glass ionomer cement (GIC) restorations in Class I tooth cavities. Cavities were prepared in excised human teeth and restored [...] Read more.
The aim of this study was the development of a test regime to determine the wear resistance and predict the clinical performance of conventional glass ionomer cement (GIC) restorations in Class I tooth cavities. Cavities were prepared in excised human teeth and restored using three conventional glass ionomer restorative materials: DeltaFil, Fuji IX GP and Ketac Universal. The restored teeth were mechanically and thermally stressed using a chewing simulator with a maximum number of 1,200,000 load cycles. Besides determining the number of cycles achieved, the abrasion volume after termination of the chewing simulation was calculated using µCT images. All teeth restored with DeltaFil reached 1,200,000 cycles without any restoration failure. Only 37.5% of the restorations each with Ketac Universal and Fuji IX GP were able to achieve the maximum cycle number. A significant lower abrasion volume for restorations with DeltaFil compared to Ketac Universal (p = 0.0099) and Fuji IX GP (p = 0.0005) was found. Laboratory chewing simulations are a useful tool to study basic wear mechanisms in a controlled setting with in-vivo related parameters. DeltaFil shows an improved wear resistance compared to other conventional GICs, indicating the high potential of this material for long-lasting Class I restorations. Full article
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17 pages, 8384 KiB  
Article
Key Technologies of Physical and Virtual Test Rig for Railway Freight Car body
by Shangchao Zhao, Xiangwei Li, Dongpo Wang and Wenquan Li
Materials 2022, 15(15), 5439; https://doi.org/10.3390/ma15155439 - 08 Aug 2022
Cited by 2 | Viewed by 1386
Abstract
On the one hand, considering that the traditional fatigue method of railway freight cars is based on damage as a parameter, the influence of stress waveform cannot be considered. On the other hand, physical experiments have the characteristics of lag, long period, and [...] Read more.
On the one hand, considering that the traditional fatigue method of railway freight cars is based on damage as a parameter, the influence of stress waveform cannot be considered. On the other hand, physical experiments have the characteristics of lag, long period, and high cost. The full-scale physical test and virtual test of car body are carried out. First of all, the data processing method of small deletion and the inverse problem load acquisition method based on data to data are proposed. Secondly, the dynamic stress calculation method with the bench as the boundary is proposed. Finally, taking the obtained load as the input of the physical and virtual bench, a new fatigue test method for simulating the running attitude of the car body line is completed. The acceleration RMS error of the C70E gondola body is less than 6%, the stress RMS is less than 13%, and the equivalent mileage is 3.125 million highway test results show that the car meets the life requirements of the car body. The inverse problem analysis results of virtual and physical tests are basically consistent, and the study of this method provides a basis for improving the fatigue reliability of freight car bodies. Full article
(This article belongs to the Special Issue Fatigue Behavior, Lifetime Prediction and Modeling of Welding Process)
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