Materials

20 pages, 10157 KiB

Open AccessEditor’s ChoiceArticle

Optimization of Resistance Spot Welding with Inserted Strips via FEM and Response Surface Methodology

by Yangyang Zhao, Wurong Wang and Xicheng Wei

Materials 2021, 14(23), 7489; https://doi.org/10.3390/ma14237489 - 6 Dec 2021

Cited by 4 | Viewed by 3350

Resistance spot welding (RSW) with inserted strips, a recent variant of traditional RSW, was usually adopted in joining thin gage steels to lower the temperature developed at the electrode surface and to extend electrode life. In order to understand the influencing mechanism how [...] Read more.

Resistance spot welding (RSW) with inserted strips, a recent variant of traditional RSW, was usually adopted in joining thin gage steels to lower the temperature developed at the electrode surface and to extend electrode life. In order to understand the influencing mechanism how the inserted strips affect the heat transfer behavior and to optimize the selection of suitable strips, an approach integrated with FEM and response surface methodology (RSM) was employed. FEM results showed that the inserted strips would not only lead to earlier initiation of weld and bigger weld size in both diameter and thickness but also lower the electrode surface temperature. Based on FEM, uniform design and RSM were further employed to build a regression model between the strip properties (i.e., electrical/thermal conductivity, thickness) and the responses (i.e., electrode tip temperature, weld diameter, and temperature at strip/sheet interface). A graphical optimization was conducted to identify a preferable strip, and a Cu55Ni45 strip with a thickness of 0.12 mm was recommended for a 0.4 mm steel sheet. Full article

(This article belongs to the Special Issue Advanced Manufacturing and Joining Technologies of Aluminum and Steel Sheets)

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27 pages, 5895 KiB

Open AccessReview

Advancing towards a Practical Magnesium Ion Battery

by Alejandro Medina, Carlos Pérez-Vicente and Ricardo Alcántara

Materials 2021, 14(23), 7488; https://doi.org/10.3390/ma14237488 - 6 Dec 2021

Cited by 23 | Viewed by 5869

Abstract

A post-lithium battery era is envisaged, and it is urgent to find new and sustainable systems for energy storage. Multivalent metals, such as magnesium, are very promising to replace lithium, but the low mobility of magnesium ion and the lack of suitable electrolytes [...] Read more.

A post-lithium battery era is envisaged, and it is urgent to find new and sustainable systems for energy storage. Multivalent metals, such as magnesium, are very promising to replace lithium, but the low mobility of magnesium ion and the lack of suitable electrolytes are serious concerns. This review mainly discusses the advantages and shortcomings of the new rechargeable magnesium batteries, the future directions and the possibility of using solid electrolytes. Special emphasis is put on the diversity of structures, and on the theoretical calculations about voltage and structures. A critical issue is to select the combination of the positive and negative electrode materials to achieve an optimum battery voltage. The theoretical calculations of the structure, intercalation voltage and diffusion path can be very useful for evaluating the materials and for comparison with the experimental results of the magnesium batteries which are not hassle-free. Full article

(This article belongs to the Section Energy Materials)

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12 pages, 3830 KiB

Open AccessArticle

Fabrication of Millable Polyurethane Elastomer/Eucommia Ulmoides Rubber Composites with Superior Sound Absorption Performance

by Yuhang Dong, Dexian Yin, Linhui Deng, Renwei Cao, Shikai Hu, Xiuying Zhao and Li Liu

Materials 2021, 14(23), 7487; https://doi.org/10.3390/ma14237487 - 6 Dec 2021

Cited by 10 | Viewed by 2834

Abstract

Sound absorbing materials combining millable polyurethane elastomer (MPU) and eucommia ulmoides rubber (EUG) were successfully fabricated via a physical blending process of EUG and MPU. The microstructure, crystallization performances, damping, mechanical and sound absorption properties of the prepared MPU/EUG composites were investigated systematically. [...] Read more.

Sound absorbing materials combining millable polyurethane elastomer (MPU) and eucommia ulmoides rubber (EUG) were successfully fabricated via a physical blending process of EUG and MPU. The microstructure, crystallization performances, damping, mechanical and sound absorption properties of the prepared MPU/EUG composites were investigated systematically. The microstructure surface of various MPU/EUG composites became rough and cracked by the gradual incorporation of EUG, resulting in a deteriorated compatibility between EUG and MPU. With the increase of EUG content, the storage modulus (E’) of various MPU/EUG composites increased in a temperature range of −50 °C to 40 °C and their loss factor (tanδ) decreased significantly, including a reduction of the tanδ of MPU/EUG (70/30) composites from 0.79 to 0.64. Specifically, the addition of EUG sharply improved the sound absorption performances of various MPU/EUG composites in a frequency range of 4.5 kHz–8 kHz. Compared with that of pure MPU, the sound absorption coefficient of the MPU/EUG (70/30) composite increased 52.2% at a pressure of 0.1 MPa and 16.8% at a pressure of 4 MPa, indicating its outstanding sound absorption properties. Full article

(This article belongs to the Topic Multiple Application for Novel and Advanced Materials)

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18 pages, 7347 KiB

Open AccessArticle

Selective Laser Melting of Pre-Alloyed NiTi Powder: Single-Track Study and FE Modeling with Heat Source Calibration

by Stanislav V. Chernyshikhin, Denis G. Firsov and Igor V. Shishkovsky

Materials 2021, 14(23), 7486; https://doi.org/10.3390/ma14237486 - 6 Dec 2021

Cited by 20 | Viewed by 2989

Abstract

Unique functional properties such as the low stiffness, superelasticity, and biocompatibility of nickel–titanium shape-memory alloys provide many applications for such materials. Selective laser melting of NiTi enables low-cost customization of devices and the manufacturing of highly complex geometries without subsequent machining. However, the [...] Read more.

Unique functional properties such as the low stiffness, superelasticity, and biocompatibility of nickel–titanium shape-memory alloys provide many applications for such materials. Selective laser melting of NiTi enables low-cost customization of devices and the manufacturing of highly complex geometries without subsequent machining. However, the technology requires optimization of process parameters in order to guarantee high mass density and to avoid deterioration of functional properties. In this work, the melt pool geometry, surface morphology, formation mode, and thermal behavior were studied. Multiple combinations of laser power and scanning speed were used for single-track preparation from pre-alloyed NiTi powder on a nitinol substrate. The experimental results show the influence of laser power and scanning speed on the depth, width, and depth-to-width aspect ratio. Additionally, a transient 3D FE model was employed to predict thermal behavior in the melt pool for different regimes. In this paper, the coefficients for a volumetric double-ellipsoid heat source were calibrated with bound optimization by a quadratic approximation algorithm, the design of experiments technique, and experimentally obtained data. The results of the simulation reveal the necessary conditions of transition from conduction to keyhole mode welding. Finally, by combining experimental and FE modeling results, the optimal SLM process parameters were evaluated as P = 77 W, V = 400 mm/s, h = 70 μm, and t = 50 μm, without printing of 3D samples. Full article

(This article belongs to the Special Issue Recent Advances in Additive Manufacturing Technologies)

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20 pages, 5516 KiB

Open AccessArticle

Experimental and Numerical Analysis of Refill Friction Stir Spot Welding of Thin AA7075-T6 Sheets

by Venkata Somi Reddy Janga, Mokhtar Awang, Mohd Fadillah Yamin, Uceu F. H. Suhuddin, Benjamin Klusemann and Jorge F. dos Santos

Materials 2021, 14(23), 7485; https://doi.org/10.3390/ma14237485 - 6 Dec 2021

Cited by 18 | Viewed by 3456

Abstract

The refill friction stir spot welding (refill FSSW) process is a solid-state joining process to produce welds without a keyhole in spot joint configuration. This study presents a thermo-mechanical model of refill FSSW, validated on experimental thermal cycles for thin aluminium sheets of [...] Read more.

The refill friction stir spot welding (refill FSSW) process is a solid-state joining process to produce welds without a keyhole in spot joint configuration. This study presents a thermo-mechanical model of refill FSSW, validated on experimental thermal cycles for thin aluminium sheets of AA7075-T6. The temperatures in the weld centre and outside the welding zone at selected points were recorded using K-type thermocouples for more accurate validation of the thermo-mechanical model. A thermo-mechanical three-dimensional refill FSSW model was built using DEFORM-3D. The temperature results from the refill FSSW numerical model are in good agreement with the experimental results. Three-dimensional material flow during plunging and refilling stages is analysed in detail and compared to experimental microstructure and hardness results. The simulation results obtained from the refill FSSW model correspond well with the experimental results. The developed 3D numerical model is able to predict the thermal cycles, material flow, strain, and strain rates which are key factors for the identification and characterization of zones as well for determining joint quality. Full article

(This article belongs to the Topic Development of Friction Stir Welding and Processing)

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15 pages, 5281 KiB

Open AccessArticle

The Effect of Graphite Additives on Magnetization, Resistivity and Electrical Conductivity of Magnetorheological Plastomer

by Nursyafiqah Zaini, Norzilawati Mohamad, Saiful Amri Mazlan, Siti Aishah Abdul Aziz, Seung-Bok Choi, Norhiwani Mohd Hapipi, Nur Azmah Nordin, Nurhazimah Nazmi and Ubaidillah Ubaidillah

Materials 2021, 14(23), 7484; https://doi.org/10.3390/ma14237484 - 6 Dec 2021

Cited by 5 | Viewed by 2439

Abstract

Common sensors in many applications are in the form of rigid devices that can react according to external stimuli. However, a magnetorheological plastomer (MRP) can offer a new type of sensing capability, as it is flexible in shape, soft, and responsive to an [...] Read more.

Common sensors in many applications are in the form of rigid devices that can react according to external stimuli. However, a magnetorheological plastomer (MRP) can offer a new type of sensing capability, as it is flexible in shape, soft, and responsive to an external magnetic field. In this study, graphite (Gr) particles are introduced into an MRP as an additive, to investigate the advantages of its electrical properties in MRPs, such as conductivity, which is absolutely required in a potential sensor. As a first step to achieve this, MRP samples containing carbonyl iron particles (CIPs) and various amounts of of Gr, from 0 to 10 wt.%, are prepared, and their magnetic-field-dependent electrical properties are experimentally evaluated. After the morphological aspect of Gr–MRP is characterized using environmental scanning electron microscopy (ESEM), the magnetic properties of MRP and Gr–MRP are evaluated via a vibrating sample magnetometer (VSM). The resistivities of the Gr–MRP samples are then tested under various applied magnetic flux densities, showing that the resistivity of Gr–MRP decreases with increasing of Gr content up to 10 wt.%. In addition, the electrical conductivity is tested using a test rig, showing that the conductivity increases as the amount of Gr additive increases, up to 10 wt.%. The conductivity of 10 wt.% Gr–MRP is found to be highest, at 178.06% higher than the Gr–MRP with 6 wt.%, for a magnetic flux density of 400 mT. It is observed that with the addition of Gr, the conductivity properties are improved with increases in the magnetic flux density, which could contribute to the potential usefulness of these materials as sensing detection devices. Full article

(This article belongs to the Special Issue Nanofabrication, Characterization and Application of Magnetic Functional Materials)

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14 pages, 35154 KiB

Open AccessArticle

Influence of 3D Printing Topology by DMLS Method on Crack Propagation

by Karel Dvorak, Jana Dvorakova, Lucie Zarybnicka and Zdenek Horak

Materials 2021, 14(23), 7483; https://doi.org/10.3390/ma14237483 - 6 Dec 2021

Cited by 6 | Viewed by 2857

Abstract

The presented text deals with research into the influence of the printing layers’ orientation on crack propagation in an AlSi10Mg material specimen, produced by additive technology, using the Direct Metal Laser Sintering (DMLS) method. It is a method based on sintering and melting [...] Read more.

The presented text deals with research into the influence of the printing layers’ orientation on crack propagation in an AlSi10Mg material specimen, produced by additive technology, using the Direct Metal Laser Sintering (DMLS) method. It is a method based on sintering and melting layers of powder material using a laser beam. The material specimen is presented as a Compact Tension test specimen and is printed in four different defined orientations (topology) of the printing layers—0°, 45°, 90°, and twice 90°. The normalized specimen is loaded cyclically, where the crack length is measured and recorded, and at the same time, the crack growth rate is determined. The evaluation of the experiment shows an apparent influence of the topology, which is essential especially for possible use in the design and technical preparation of the production of real machine parts in industrial practice. Simultaneously with the measurement results, other influencing factors are listed, especially product postprocessing and the measurement method used. The hypothesis of crack propagation using Computer Aided Engineering/Finite Element Method (CAE/FEM) simulation is also stated here based on the achieved results. Full article

(This article belongs to the Topic Surface Treatments for Protecting from Fracture and Fatigue Damage)

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17 pages, 3124 KiB

Open AccessArticle

Raphia-Microorganism Composite Biosorbent for Lead Ion Removal from Aqueous Solutions

by Paweł Staroń and Jarosław Chwastowski

Materials 2021, 14(23), 7482; https://doi.org/10.3390/ma14237482 - 6 Dec 2021

Cited by 25 | Viewed by 2269

Abstract

This study investigated the possibility of obtaining a raphia-microorganism composite for removing lead ions from aqueous solutions using immobilized yeast cells Saccharomyces cerevisiae on Raphia farinifera fibers. The obtained biocomposite was characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. Studies [...] Read more.

This study investigated the possibility of obtaining a raphia-microorganism composite for removing lead ions from aqueous solutions using immobilized yeast cells Saccharomyces cerevisiae on Raphia farinifera fibers. The obtained biocomposite was characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. Studies were conducted to determine the influence of contact time, initial concentration of Pb(II), and pH allowed for the selection of nonlinear equilibrium and kinetic models. The results showed that the biocomposite had a better Pb(II) removal capacity in comparison to the raphia fibers alone, and its maximum Pb(II) adsorption capacity was 94.8 mg/g. The model that best describes Pb(II) sorption was the Temkin isotherm model, while kinetic studies confirmed the chemical nature of the sorption process following the Elovich model. The obtained research results provide new information on the full use of the adsorption function of biomass and the ubiquitous microbial resources and their use in the remediation of aqueous environments contaminated with heavy metals. Full article

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25 pages, 8527 KiB

Open AccessArticle

Localized Corrosion Resistance on Additively Manufactured Ti Alloys by Means of Electrochemical Critical Localized Corrosion Potential in Biomedical Solution Environments

by Dong-Il Seo and Jae-Bong Lee

Materials 2021, 14(23), 7481; https://doi.org/10.3390/ma14237481 - 6 Dec 2021

Cited by 7 | Viewed by 2221

Abstract

This study proposes a new method, electrochemical critical localized corrosion potential (E-CLCP), in order to evaluate localized corrosion resistance of biomedical additive manufacturing (AM) titanium (Ti) alloys. The procedures for determining E-CLCP are completely different from that of the electrochemical critically localized corrosion [...] Read more.

This study proposes a new method, electrochemical critical localized corrosion potential (E-CLCP), in order to evaluate localized corrosion resistance of biomedical additive manufacturing (AM) titanium (Ti) alloys. The procedures for determining E-CLCP are completely different from that of the electrochemical critically localized corrosion temperature (E-CLCT) method (ISO 22910:2020). However, its application should be limited to pH and temperature of the human body because of the temperature scan. E-CLCP displays the localized corrosion resistance of AM Ti alloys based on the human body’s repassivation kinetics, whereas E-CLCT displays the localized corrosion resistance of the alloys based on passive film breakdown in much harsher corrosive environments. Full article

(This article belongs to the Special Issue Additive Manufacturing (AM) of Biomaterials)

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15 pages, 13232 KiB

Open AccessArticle

Fatigue Properties of Hot-Dip Galvanized AISI 1020 Normalized Steel in Tension–Compression and Tension–Tension Loading

by Shatumbu Thomas Alweendo, Motoaki Morita, Kayo Hasegawa and Shinichi Motoda

Materials 2021, 14(23), 7480; https://doi.org/10.3390/ma14237480 - 6 Dec 2021

Cited by 10 | Viewed by 4082

Abstract

Since hot-dip galvanizing causes a heat effect on cold-worked steel substrate and produces a coating layer comprised of distinct phases with varying mechanical properties, the fatigue mechanism of hot-dip galvanized steel is very complex and hard to clarify. In this study, AISI 1020 [...] Read more.

Since hot-dip galvanizing causes a heat effect on cold-worked steel substrate and produces a coating layer comprised of distinct phases with varying mechanical properties, the fatigue mechanism of hot-dip galvanized steel is very complex and hard to clarify. In this study, AISI 1020 steel that has been normalized to minimize susceptibility to the heat effect was used to clarify the effect of the galvanizing layer on the tensile and fatigue properties. The galvanizing layer causes a reduction in the yield point, tensile strength, and fatigue strength. The reduction in the fatigue strength was more significant in the high cycle fatigue at R = 0.5 and 0.01 and in the low cycle fatigue at R = 0.5. The galvanizing layer seems to have very little effect on the fatigue strength at R = −1.0 in the low and high cycle fatigue. Since the fatigue strengths at R = 0.01 and −1.0 in the low cycle fatigue were strongly related to the tensile strength of the substrate, the cracking of galvanized steel was different than that of non-galvanized steel. The fatigue strength of galvanized steel at R = 0.5 dropped remarkably in the low cycle fatigue in comparison to the non-galvanized steel, and many cracks clearly occurred in the galvanizing layer. The galvanizing layer reduced the fatigue strength only under tension–tension loading. We believe that the findings in this study will be useful in the fatigue design of hot-dip galvanized steel. Full article

(This article belongs to the Topic Metallurgical and Materials Engineering)

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20 pages, 1932 KiB

Open AccessArticle

Analysis and Optimization of Dimensional Accuracy and Porosity of High Impact Polystyrene Material Printed by FDM Process: PSO, JAYA, Rao, and Bald Eagle Search Algorithms

by Manjunath Patel Gowdru Chandrashekarappa, Ganesh Ravi Chate, Vineeth Parashivamurthy, Balakrishnamurthy Sachin Kumar, Mohd Amaan Najeeb Bandukwala, Annan Kaisar, Khaled Giasin, Danil Yurievich Pimenov and Szymon Wojciechowski

Materials 2021, 14(23), 7479; https://doi.org/10.3390/ma14237479 - 6 Dec 2021

Cited by 13 | Viewed by 2697

Abstract

High impact polystyrene (HIPS) material is widely used for low-strength structural applications. To ensure proper function, dimensional accuracy and porosity are at the forefront of industrial relevance. The dimensional accuracy cylindricity error (CE) and porosity of printed parts are influenced mainly by the [...] Read more.

High impact polystyrene (HIPS) material is widely used for low-strength structural applications. To ensure proper function, dimensional accuracy and porosity are at the forefront of industrial relevance. The dimensional accuracy cylindricity error (CE) and porosity of printed parts are influenced mainly by the control variables (layer thickness, shell thickness, infill density, print speed of the fused deposition modeling (FDM) process). In this study, a central composite design (CCD) matrix was used to perform experiments and analyze the complete insight information of the process (control variables influence on CE and porosity of FDM parts). Shell thickness for CE and infill density for porosity were identified as the most significant factors. Layer thickness interaction with shell thickness, infill density (except for CE), and print speed were found to be significant for both outputs. The interaction factors, i.e., shell thickness and infill density, were insignificant (negligible effect) for both outputs. The models developed produced a better fit for regression with an R² equal to 94.56% for CE, and 99.10% for porosity, respectively. Four algorithms (bald eagle search optimization (BES), particle swarm optimization (PSO), RAO-3, and JAYA) were applied to determine optimal FDM conditions while examining six case studies (sets of weights assigned for porosity and CE) focused on minimizing both CE and porosity. BES and RAO-3 algorithms determined optimal conditions (layer thickness: 0.22 mm; shell thickness: 2 mm; infill density: 100%; print speed: 30 mm/s) at a reduced computation time equal to 0.007 s, differing from JAYA and PSO, which resulted in an experimental CE of 0.1215 mm and 2.5% of porosity in printed parts. Consequently, BES and RAO-3 algorithms are efficient tools for the optimization of FDM parts. Full article

(This article belongs to the Special Issue Additive and Subtractive Manufacturing of Advanced Materials: Applications, Future Trends and Perspectives of Industry 4.0)

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10 pages, 3602 KiB

Open AccessArticle

Microstructures of HfO_x Films Prepared via Atomic Layer Deposition Using La(NO₃)₃·6H₂O Oxidants

by Seon Yong Kim, Yong Chan Jung, Sejong Seong, Taehoon Lee, In-Sung Park and Jinho Ahn

Materials 2021, 14(23), 7478; https://doi.org/10.3390/ma14237478 - 6 Dec 2021

Cited by 6 | Viewed by 2552

Abstract

Hafnium oxide (HfO_x) films have a wide range of applications in solid-state devices, including metal–oxide–semiconductor field-effect transistors (MOSFETs). The growth of HfO_x films from the metal precursor tetrakis(ethylmethylamino) hafnium with La(NO₃)₃·6H₂O solution (LNS) as [...] Read more.

Hafnium oxide (HfO_x) films have a wide range of applications in solid-state devices, including metal–oxide–semiconductor field-effect transistors (MOSFETs). The growth of HfO_x films from the metal precursor tetrakis(ethylmethylamino) hafnium with La(NO₃)₃·6H₂O solution (LNS) as an oxidant was investigated. The atomic layer deposition (ALD) conditions were optimized, and the chemical state, surface morphology, and microstructure of the prepared films were characterized. Furthermore, to better understand the effects of LNS on the deposition process, HfO_x films deposited using a conventional oxidant (H₂O) were also prepared. The ALD process using LNS was observed to be self-limiting, with an ALD temperature window of 200–350 °C and a growth rate of 1.6 Å per cycle, two times faster than that with H₂O. HfO_x films deposited using the LNS oxidant had smaller crystallites than those deposited using H₂O, as well as more suboxides or defects because of the higher number of grain boundaries. In addition, there was a difference in the preferred orientations of the HfO_x films deposited using LNS and H₂O, and consequently, a difference in surface energy. Finally, a film growth model based on the surface energy difference was proposed to explain the observed growth rate and crystallite size trends. Full article

(This article belongs to the Special Issue Atomic Layer Deposition Technique in Material Science)

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11 pages, 3128 KiB

Open AccessArticle

Antibacterial Polymers Based on Poly(2-hydroxyethyl methacrylate) and Thiazolium Groups with Hydrolytically Labile Linkages Leading to Inactive and Low Cytotoxic Compounds

by Rocío Cuervo-Rodríguez, Fátima López-Fabal, Alexandra Muñoz-Bonilla and Marta Fernández-García

Materials 2021, 14(23), 7477; https://doi.org/10.3390/ma14237477 - 6 Dec 2021

Cited by 4 | Viewed by 2478

Abstract

Herein, we develop a well-defined antibacterial polymer based on poly(2-hydroxyethyl methacrylate) (PHEMA) and a derivative of vitamin B1, easily degradable into inactive and biocompatible compounds. Hence, thiazole moiety was attached to HEMA monomer through a carbonate pH-sensitive linkage and the resulting monomer was [...] Read more.

Herein, we develop a well-defined antibacterial polymer based on poly(2-hydroxyethyl methacrylate) (PHEMA) and a derivative of vitamin B1, easily degradable into inactive and biocompatible compounds. Hence, thiazole moiety was attached to HEMA monomer through a carbonate pH-sensitive linkage and the resulting monomer was polymerized via reversible addition-fragmentation chain transfer (RAFT) polymerization. N-alkylation reaction of the thiazole groups leads to cationic polymer with thiazolium groups. This polymer exhibits excellent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) with an MIC value of 78 µg mL⁻¹, whereas its degradation product, thiazolium small molecule, was found to be inactive. Hemotoxicity studies confirm the negligible cytotoxicity of the degradation product in comparison with the original antibacterial polymer. The degradation of the polymer at physiological pH was found to be progressive and slow, thus the cationic polymer is expected to maintain its antibacterial characteristics at physiological conditions for a relative long period of time before its degradation. This degradation minimizes antimicrobial pollution in the environment and side effects in the body after eradicating bacterial infection. Full article

(This article belongs to the Special Issue Advanced Antimicrobial Materials)

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15 pages, 3261 KiB

Open AccessArticle

Design and Simulation Study of the Induction Heated Injection Mold with Sliders

by Paweł Muszyński, Przemysław Poszwa, Krzysztof Mrozek, Michał Zielinski, Piotr Dalewski and Michał Kowal

Materials 2021, 14(23), 7476; https://doi.org/10.3390/ma14237476 - 6 Dec 2021

Cited by 1 | Viewed by 2871

Abstract

In order to increase the quality of the products manufactured by injection molding, RTC technology can be used to achieve higher mold temperatures. As a result, the path of the injected melt can be extended, allowing the production of parts with more complex [...] Read more.

In order to increase the quality of the products manufactured by injection molding, RTC technology can be used to achieve higher mold temperatures. As a result, the path of the injected melt can be extended, allowing the production of parts with more complex shapes and greater length. Induction heating allows heating only selected forming surfaces of the mold which increases the speed and efficiency of the process. This paper presents the concept of a detachable inductor integrated with sliders to enable the application of this technology in an injection mold with sliders, along with the theoretical model used to perform the tests. First, the effect of the magnetic concentrator shape on the process was analyzed. This was followed by a simulation study of the influence of process parameters: heating time, frequency, and electric current. An extensive analysis of the test results of the temperature distribution on the insert allowed for the selection of parameter sets that would enable obtaining the desired surface temperature without a major increase in process time. The results of simulation studies confirm the possible applications and present the range of parameters for obtaining the optimal process. Full article

(This article belongs to the Special Issue Polymers and Injection Molding Simulation)

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13 pages, 4137 KiB

Open AccessArticle

Hydroxyapatite Film Coating by Er:YAG Pulsed Laser Deposition Method for the Repair of Enamel Defects

by Liji Chen, Shigeki Hontsu, Satoshi Komasa, Ei Yamamoto, Yoshiya Hashimoto and Naoyuki Matsumoto

Materials 2021, 14(23), 7475; https://doi.org/10.3390/ma14237475 - 6 Dec 2021

Cited by 12 | Viewed by 2980

Abstract

There are treatments available for enamel demineralization or acid erosion, but they have limitations. We aimed to manufacture a device that could directly form a hydroxyapatite (HAp) film coating on the enamel with a chairside erbium-doped yttrium aluminum garnet (Er:YAG) laser using the [...] Read more.

There are treatments available for enamel demineralization or acid erosion, but they have limitations. We aimed to manufacture a device that could directly form a hydroxyapatite (HAp) film coating on the enamel with a chairside erbium-doped yttrium aluminum garnet (Er:YAG) laser using the pulsed laser deposition (PLD) method for repairing enamel defects. We used decalcified bovine enamel specimens and compacted α-tricalcium phosphate (α-TCP) as targets of Er:YAG-PLD. With irradiation, an α-TCP coating layer was immediately deposited on the specimen surface. The morphological, mechanical, and chemical characteristics of the coatings were evaluated using scanning electron microscopy (SEM), scanning probe microscopy (SPM), X-ray diffractometry (XRD), and a micro-Vickers hardness tester. Wear resistance, cell attachment of the HAp coatings, and temperature changes during the Er:YAG-PLD procedure were also observed. SEM demonstrated that the α-TCP powder turned into microparticles by irradiation. XRD peaks revealed that the coatings were almost hydrolyzed into HAp within 2 days. Micro-Vickers hardness indicated that the hardness lost by decalcification was almost recovered by the coatings. The results suggest that the Er:YAG-PLD technique is useful for repairing enamel defects and has great potential for future clinical applications. Full article

(This article belongs to the Special Issue Advances in Dental Bio-Nanomaterials)

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14 pages, 2487 KiB

Open AccessArticle

Effect of Cooling Rate during Glazing on the Mechanical and Optical Properties of Monolithic Zirconia with 3 mol% Yttria Content

by Mi-Hyang Cho and Hyo-Joung Seol

Materials 2021, 14(23), 7474; https://doi.org/10.3390/ma14237474 - 6 Dec 2021

Cited by 6 | Viewed by 1981

Abstract

Glazing is the final heat treatment process in the manufacturing of a monolithic zirconia prosthesis. Herein, the effect of cooling rate during zirconia glazing was investigated. A 3 mol% yttria-stabilized tetragonal zirconia polycrystal was glazed at the general cooling rate suggested by the [...] Read more.

Glazing is the final heat treatment process in the manufacturing of a monolithic zirconia prosthesis. Herein, the effect of cooling rate during zirconia glazing was investigated. A 3 mol% yttria-stabilized tetragonal zirconia polycrystal was glazed at the general cooling rate suggested by the manufacturer, as well as at higher and lower cooling rates, and the differences in flexural strength, hardness, optical properties, and crystal structure were evaluated. A higher cooling rate did not affect the flexural strength, hardness, grain size, optical properties, or crystal structure; however, the Weibull modulus decreased by 1.3. A lower cooling rate did not affect the flexural strength, optical properties, or crystal structure; however, the Weibull characteristic strength increased by 26.7 MPa and the Weibull modulus increased by 0.9. The decrease in hardness and the increase in grain size were statistically significant; however, the numerical differences were negligible. This study revealed that a lower cooling rate provides more reliable flexural strength. Therefore, glazing can proceed at a general cooling rate, which takes 3–4 min; however, glazing at a lower cooling rate will provide a more consistent flexural strength if desired, despite being time-consuming. Full article

(This article belongs to the Special Issue Advances in Ceramics and Glass: Processing, Sintering, Properties and Applications)

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11 pages, 3651 KiB

Open AccessArticle

Mössbauer Studies of Narrow Fractions of Fly Ash Formed after Combustion of Ekibastuz Coal

by Mikhail Vereshchak, Irina Manakova, Adilkhan Shokanov and Sayabek Sakhiyev

Materials 2021, 14(23), 7473; https://doi.org/10.3390/ma14237473 - 6 Dec 2021

Cited by 5 | Viewed by 1678

Abstract

Nuclear gamma-resonance spectroscopy on ⁵⁷Fe nuclei, X-ray diffraction, and scanning electron microscopy have been used to study the narrow fractions of fly ash formed after combustion of the Ekibastuz coal. Two groups of samples of magnetic (ferrospheres) and non-magnetic type have been [...] Read more.

Nuclear gamma-resonance spectroscopy on ⁵⁷Fe nuclei, X-ray diffraction, and scanning electron microscopy have been used to study the narrow fractions of fly ash formed after combustion of the Ekibastuz coal. Two groups of samples of magnetic (ferrospheres) and non-magnetic type have been separated by granulometric and magnetic separation. A number of regularities associated with the granules size of fly ash have been established. According to the data of Mössbauer spectroscopy, a decrease in the magnetically ordered contribution has been identified with the growth of the particle size. After magnetic separation, iron in ferrospheres was found mainly in the structure of Fe₃O₄/γ-Fe₂O₃ and α-Fe₂O₃. The dominant phase was Fe₃O₄ (60–77%), the amount of which decreases with the growth of the grain size. With the growth of the particle size, the ratio of [Fe]^tetra/[Fe]^octa positions occupancy in Fe₃O₄ approaches 0.5; the structure of magnetite tends to the stoichiometric composition. α-Fe was found in the composition of ferrospheres, and a mechanism of its formation was proposed. The main components of the non-magnetic fractions of fly ash are mullite, hercynite, and silicate glass. Full article

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18 pages, 6714 KiB

Open AccessArticle

Hydrothermal Treatment of Arsenopyrite Particles with CuSO₄ Solution

by Aleksei Kritskii and Stanislav Naboichenko

Materials 2021, 14(23), 7472; https://doi.org/10.3390/ma14237472 - 6 Dec 2021

Cited by 5 | Viewed by 1905

Abstract

The nature of the hydrothermal reaction between arsenopyrite particles (FeAsS) and copper sulfate solution (CuSO₄) was investigated in this study. The effects of temperature (443–523 K), CuSO₄ (0.08–0.96 mol/L) and H₂SO₄ (0.05–0.6 mol/L) concentrations, reaction time (1–120 [...] Read more.

The nature of the hydrothermal reaction between arsenopyrite particles (FeAsS) and copper sulfate solution (CuSO₄) was investigated in this study. The effects of temperature (443–523 K), CuSO₄ (0.08–0.96 mol/L) and H₂SO₄ (0.05–0.6 mol/L) concentrations, reaction time (1–120 min), stirring speed (40–100 rpm) and particle size (10–100 μm) on the FeAsS conversion were studied. The FeAsS conversion was significant at >503 K, and it is suggested that the reaction is characterized by the formation of a thin layer of metallic copper (Cu⁰) and elemental sulfur (S⁰) around the unreacted FeAsS core. The shrinking core model (SCM) was applied for describing the process kinetics, and the rate of the overall reaction was found to be controlled by product layer diffusion, while the overall process was divided into two stages: (Stage 1: mixed chemical reaction/product layer diffusion-controlled) interaction of FeAsS with CuSO₄ on the mineral’s surface with the formation of Cu¹⁺ and Fe²⁺ sulfates, arsenous acid, S⁰, and subsequent diffusion of the reagent (Cu²⁺) and products (As³⁺ and Fe²⁺) through the gradually forming layer of Cu⁰ and molten S⁰; (Stage 2: product layer diffusion-controlled) the subsequent interaction of CuSO₄ with FeAsS resulted in the formation of a denser and less porous Cu⁰ and S⁰ layer, which complicates the countercurrent diffusion of Cu²⁺, Cu¹⁺, and Fe²⁺ across the layer to the unreacted FeAsS core. The reaction orders with respect to CuSO₄ and H₂SO₄ were calculated as 0.41 and −0.45 for Stage 1 and 0.35 and −0.5 for Stage 2. The apparent activation energies of 91.67 and 56.69 kJ/mol were obtained for Stages 1 and 2, respectively. Full article

(This article belongs to the Special Issue Research Progress on the Extractive Metallurgy)

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34 pages, 17856 KiB

Open AccessArticle

Characterization of Three Amu-Darya Basin Clays in Ceramic Brick Industry and Their Applications with Brick Waste

by Serdar Korpayev, Meretdurdy Bayramov, Serdar Durdyev and Hemra Hamrayev

Materials 2021, 14(23), 7471; https://doi.org/10.3390/ma14237471 - 6 Dec 2021

Cited by 9 | Viewed by 2947

Abstract

This study examined the chemical, mineralogical, physical, thermal, and technological characteristics of the Dostluk (DM), Halach (HM), and Sakar (HM) clay deposits located in the Amu-Darya basin of Turkmenistan. The potential suitability of these deposits was evaluated for the local ceramic brick industry. [...] Read more.

This study examined the chemical, mineralogical, physical, thermal, and technological characteristics of the Dostluk (DM), Halach (HM), and Sakar (HM) clay deposits located in the Amu-Darya basin of Turkmenistan. The potential suitability of these deposits was evaluated for the local ceramic brick industry. The chemical and mineralogical features were identified by X-ray fluorescence (XRF), ion chromatography (IC), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) techniques. The physical properties were characterized by granulometric analysis by sieving, particle size distribution, scanning electron microscopy/optic analysis, specific surface area, Pfefferkon’s plasticity index, reabsorption, shrinkage, water absorption, mechanical (compression and bending), and freeze–thaw durability tests. The thermal methods were performed using dilatometry and thermogravimetric/differential thermal analyzer (TG/DTA). The test samples for the different clay deposits were extruded, dried, and fired at three different temperatures of 850 °C, 950 °C, and 1050 °C. While the Dostluk and Sakar clays have high plasticity, Halach clay has been found to have low plasticity. The mechanical and freeze–thaw durability tests demonstrated that the outcomes of the clays of different origins were sufficient, achieving compressive strengths of over 10 MPa and mass loss less than 3%, which are acceptable by industry standards. Semi-industrial processed hollow bricks demonstrated promising characteristics. While the Dostluk and Sakar clay-based brick specimens were visibly free of cracks, the Halach specimens showed some cracks. The physical and mechanical improvements of these clays were performed with three mixtures, which are M1 (80 mass% DM + 20 mass% brick waste), M2 (85 mass% SM + 15 mass% brick waste), and M3 (70 mass% HM + 25 mass% SM and 5 mass% brick waste) for the brick industry. Full article

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15 pages, 4291 KiB

Open AccessArticle

Effect of Gd₂O₃ Addition on the Microstructure and Properties of Gd₂O₃-Yb₂O₃-Y₂O₃-ZrO₂ (GYYZO) Ceramics

by Pei-Hu Gao, Sheng-Cong Zeng, Can Jin, Bo Zhang, Bai-Yang Chen, Zhong Yang, Yong-Chun Guo, Min-Xian Liang, Jian-Ping Li, Quan-Ping Li, Yong-Qing Lu, Lu Jia and Dan Zhao

Materials 2021, 14(23), 7470; https://doi.org/10.3390/ma14237470 - 6 Dec 2021

Cited by 9 | Viewed by 2608

Abstract

Gd and Yb elements have high chemical stability, which can stabilize the solid solution in ZrO₂. Gd₂O₃ and Yb₂O₃ have high melting points, and good oxidation resistance in extreme environments, stable chemical properties. Therefore, Gd [...] Read more.

Gd and Yb elements have high chemical stability, which can stabilize the solid solution in ZrO₂. Gd₂O₃ and Yb₂O₃ have high melting points, and good oxidation resistance in extreme environments, stable chemical properties. Therefore, Gd₂O₃ and Yb₂O₃ were added to ZrO₂ to stabilize oxides, improve the high temperature stability, and effectively decrease the thermal conductivity at high temperature. In this work, 5 wt% Yb₂O₃ and 5 wt%, 10 wt%, 15 wt% Gd₂O₃ were doped into 8 wt% Y₂O₃ stabilized ZrO₂ (8YSZ) powders as thermal barrier coating materials, and sintered at 1650 °C for 6 h, 12 h, 24 h. The effects of Gd₂O₃ addition on the microstructure, density, thermal conductivity, hardness, and fracture toughness of Gd₂O₃-Yb₂O₃-Y₂O₃-ZrO₂ (GYYZO) bulk composite ceramics were investigated. It was found that the densification of the 8YSZ bulk and GYYZO bulk with 15 wt% Gd₂O₃ reached 96.89% and 96.22% sintered at 1650 °C for 24 h. With the increase of Gd₂O₃ addition, the hardness, elastic modulus and fracture toughness of the GYYZO bulk increased and the thermal conductivity and thermal expansion coefficient of the GYYZO bulk decreased. GYYZO bulk with 15 wt% Gd₂O₃ sintered at 1650 °C for 24h had the highest hardness, elastic modulus and fracture toughness of 15.61 GPa, 306.88 GPa, 7.822 MPa·m^0.5, and the lowest thermal conductivity and thermal expansion coefficient of 1.04 W/(m·k) and 7.89 × 10⁻⁶/°C at 1100 °C, respectively. The addition of Gd₂O₃ into YSZ could not only effectively reduce the thermal conductivity but also improve the mechanical properties, which would improve the thermal barrier coatings’ performances further. Full article

(This article belongs to the Special Issue Advances in Metal and Ceramic Matrix Composites)

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10 pages, 2437 KiB

Open AccessArticle

Robust Heterojunctions of Metallic Alloy and Carbon Fiber-Reinforced Composite Induced by Laser Processing

by Haipeng Wang, Peng Yan and Yingchun Guan

Materials 2021, 14(23), 7469; https://doi.org/10.3390/ma14237469 - 6 Dec 2021

Cited by 8 | Viewed by 2475

Abstract

The development of heterojunctions with a strong bonding interface between metals and non-metals has attracted much attention owing to their great potential for use in lightweight structures. Laser joining technology, which emerged as a fast and reliable method, has proven its feasibility and [...] Read more.

The development of heterojunctions with a strong bonding interface between metals and non-metals has attracted much attention owing to their great potential for use in lightweight structures. Laser joining technology, which emerged as a fast and reliable method, has proven its feasibility and unique advantages in joining metal to polymer matrix composites. Herein, an optimized laser joining configuration has been employed to realize high-quality joining of titanium alloy and carbon fiber-reinforced composite. Cross-sectional microstructures of laser-produced joints reveal that micro-bubbles near the interface have been effectively suppressed and eliminated due to the continual clamping pressure applied to the joined area during the joining process. Tensile tests suggest that the joint strength increases with structure density on a titanium alloy surface, and the greatest fracture strength of joints reaches more than 60 MPa even after experiencing a high–low temperature alternating aging test. For higher structure density (>95%), the joints fail by the fracture of parent plastics near the joined area due to the tensile-loading-induced peel stress at the edges of the overlap region. Otherwise, the joints fail by interfacial shear fracture with breakage when the structure density is lower than 91.5%. The obtained high-performance heterojunctions show great potential in the aerospace and automotive fields. Full article

(This article belongs to the Special Issue Feature Paper in the Section 'Polymeric Materials')

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18 pages, 1087 KiB

Open AccessReview

Progress and Current Limitations of Materials for Artificial Bile Duct Engineering

by Qiqi Sun, Zefeng Shen, Xiao Liang, Yingxu He, Deling Kong, Adam C. Midgley and Kai Wang

Materials 2021, 14(23), 7468; https://doi.org/10.3390/ma14237468 - 6 Dec 2021

Cited by 12 | Viewed by 3483

Abstract

Bile duct injury (BDI) and bile tract diseases are regarded as prominent challenges in hepatobiliary surgery due to the risk of severe complications. Hepatobiliary, pancreatic, and gastrointestinal surgery can inadvertently cause iatrogenic BDI. The commonly utilized clinical treatment of BDI is biliary-enteric anastomosis. [...] Read more.

Bile duct injury (BDI) and bile tract diseases are regarded as prominent challenges in hepatobiliary surgery due to the risk of severe complications. Hepatobiliary, pancreatic, and gastrointestinal surgery can inadvertently cause iatrogenic BDI. The commonly utilized clinical treatment of BDI is biliary-enteric anastomosis. However, removal of the Oddi sphincter, which serves as a valve control over the unidirectional flow of bile to the intestine, can result in complications such as reflux cholangitis, restenosis of the bile duct, and cholangiocarcinoma. Tissue engineering and biomaterials offer alternative approaches for BDI treatment. Reconstruction of mechanically functional and biomimetic structures to replace bile ducts aims to promote the ingrowth of bile duct cells and realize tissue regeneration of bile ducts. Current research on artificial bile ducts has remained within preclinical animal model experiments. As more research shows artificial bile duct replacements achieving effective mechanical and functional prevention of biliary peritonitis caused by bile leakage or obstructive jaundice after bile duct reconstruction, clinical translation of tissue-engineered bile ducts has become a theoretical possibility. This literature review provides a comprehensive collection of published works in relation to three tissue engineering approaches for biomimetic bile duct construction: mechanical support from scaffold materials, cell seeding methods, and the incorporation of biologically active factors to identify the advancements and current limitations of materials and methods for the development of effective artificial bile ducts that promote tissue regeneration. Full article

(This article belongs to the Special Issue Biomimetic Composites and Design)

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13 pages, 4053 KiB

Open AccessArticle

Finite Element Analysis on Initial Crack Site of Porous Structure Fabricated by Electron Beam Additive Manufacturing

by Meng-Hsiu Tsai, Chia-Ming Yang, Yu-Xuan Hung, Chao-Yong Jheng, Yen-Ju Chen, Ho-Chung Fu and In-Gann Chen

Materials 2021, 14(23), 7467; https://doi.org/10.3390/ma14237467 - 6 Dec 2021

Cited by 4 | Viewed by 2210

Abstract

Ti6Al4V specimens with porous structures can be fabricated by additive manufacturing to obtain the desired Young’s modulus. Their mechanical strength and deformation behavior can be evaluated using finite element analysis (FEA), with various models and simulation methodologies described in the existing literature. Most [...] Read more.

Ti6Al4V specimens with porous structures can be fabricated by additive manufacturing to obtain the desired Young’s modulus. Their mechanical strength and deformation behavior can be evaluated using finite element analysis (FEA), with various models and simulation methodologies described in the existing literature. Most studies focused on the evaluation accuracy of the mechanical strength and deformation behavior using complex models. This study presents a simple elastic model for brittle specimens followed by an electron beam additive manufacturing (EBAM) process to predict the initial crack site and threshold of applied stress related to the failure of cubic unit lattice structures. Six cubic lattice specimens with different porosities were fabricated by EBAM, and compression tests were performed and compared to the FEA results. In this study, two different types of deformation behavior were observed in the specimens with low and high porosities. The adopted elastic model and the threshold of applied stress calculated via FEA showed good capabilities for predicting the initial crack sites of these specimens. The methodology presented in this study should provide a simple yet accurate method to predict the fracture initiation of porous structure parts. Full article

(This article belongs to the Topic Material and Process Innovations for 3D Printing Applications)

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11 pages, 4668 KiB

Open AccessArticle

Tribo-oxide Competition and Oxide Layer Formation of Ti₃SiC₂/CaF₂ Self-Lubricating Composites during the Friction Process in a Wide Temperature Range

by Rui Zhang, Wei Feng and Fuyan Liu

Materials 2021, 14(23), 7466; https://doi.org/10.3390/ma14237466 - 6 Dec 2021

Cited by 3 | Viewed by 2018

Abstract

Ti₃SiC₂/CaF₂ composites were prepared by the spark plasma sintering (SPS) process. Both the microstructure of Ti₃SiC₂/CaF₂ and the influence of test temperature on the tribological behavior of the Ti₃SiC₂/CaF [...] Read more.

Ti₃SiC₂/CaF₂ composites were prepared by the spark plasma sintering (SPS) process. Both the microstructure of Ti₃SiC₂/CaF₂ and the influence of test temperature on the tribological behavior of the Ti₃SiC₂/CaF₂composites were investigated. The synergistic effect of friction and oxidation was evaluated by analyzing the worn surface morphology. The results showed that Ti₃SiC₂/CaF₂ were still brittle materials after adding CaF₂, which was in agreement with Ti₃SiC₂. The hardness, relative density, flexural strength and compressive strength of the Ti₃SiC₂/CaF₂ composites were slightly lower than those of Ti₃SiC₂, and the addition of CaF₂ decreased the decomposition temperature of Ti₃SiC₂ from 1350 to 1300 °C. Simultaneously, as the temperature of the test increased, the friction coefficient of Ti₃SiC₂/CaF₂ showed a downward trend (from 0.81 to 0.34), and its the wear rate was insensitive. Full article

(This article belongs to the Topic Metallurgical and Materials Engineering)

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7 pages, 1098 KiB

Open AccessArticle

Photoresponse Dimensionality of Organic Field-Effect Transistor

by Tomas Vincze, Michal Micjan, Juraj Nevrela, Martin Donoval and Martin Weis

Materials 2021, 14(23), 7465; https://doi.org/10.3390/ma14237465 - 6 Dec 2021

Cited by 3 | Viewed by 2285

Abstract

Organic field-effect transistors have been envisioned for advanced photodetectors because the organic semiconductors provide unique absorption characteristics, low-cost fabrication, or compatibility with flexible substrates. However, the response time of organic phototransistors still does not reach the required application level. Here, we report the [...] Read more.

Organic field-effect transistors have been envisioned for advanced photodetectors because the organic semiconductors provide unique absorption characteristics, low-cost fabrication, or compatibility with flexible substrates. However, the response time of organic phototransistors still does not reach the required application level. Here, we report the photoresponse of copper phthalocyanine phototransistor in a steady state and under pulsed illumination. The detailed analysis based on the random walk among a field of traps was used to evaluate the dimensionality of electron transport in a device. Full article

(This article belongs to the Special Issue Organic-Semiconductor Based Devices)

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19 pages, 6247 KiB

Open AccessArticle

Role of Coating Processes on the Corrosion Kinetics and Mechanism of Zinc in Artificial Seawater

by Jitendra Kumar Singh, Soumen Mandal, Raihana Jannat Adnin, Han-Seung Lee and Hyun-Min Yang

Materials 2021, 14(23), 7464; https://doi.org/10.3390/ma14237464 - 6 Dec 2021

Cited by 9 | Viewed by 2497

Abstract

Zinc (Zn) coating is being used to protect steel structures from corrosion. There are different processes to deposit the coating onto a steel substrate. Therefore, in the present study, a 100 µm thick Zn coating was deposited by arc and plasma arc thermal [...] Read more.

Zinc (Zn) coating is being used to protect steel structures from corrosion. There are different processes to deposit the coating onto a steel substrate. Therefore, in the present study, a 100 µm thick Zn coating was deposited by arc and plasma arc thermal spray coating processes, and the corrosion resistance performance was evaluated in artificial seawater. Scanning electron microscopy (SEM) results showed that the arc thermal spray coating exhibited splats and inflight particles, whereas plasma arc spraying showed a uniform and dense morphology. When the exposure periods were extended up to 23 d, the corrosion resistance of the arc as well as the plasma arc thermal spray coating increased considerably. This is attributed to the blocking characteristics of the defects by the stable hydrozincite (Zn₅(OH)₆(CO₃)₂). Full article

(This article belongs to the Special Issue Corrosion and Corrosion Inhibition of Metals and Their Alloys)

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20 pages, 12038 KiB

Open AccessArticle

Effects of Fillet Weld Size and Sleeve Material Strength on the Residual Stress Distribution and Structural Safety While Implementing the New Sleeve Repair Process

by Hongjie Zhang, Tao Han, Yong Wang and Qian Wu

Materials 2021, 14(23), 7463; https://doi.org/10.3390/ma14237463 - 5 Dec 2021

Cited by 4 | Viewed by 3308

Abstract

The process optimization and structural safety improvement of the in-service repair welding of the X80 pipeline are very important. In this paper, the temperature, microstructure, and stress distribution were analyzed using the combination of TMM (thermal-metallurgical-mechanical) simulations and the corresponding verification experiments. The [...] Read more.

The process optimization and structural safety improvement of the in-service repair welding of the X80 pipeline are very important. In this paper, the temperature, microstructure, and stress distribution were analyzed using the combination of TMM (thermal-metallurgical-mechanical) simulations and the corresponding verification experiments. The effects of the sleeve material strength and the fillet weld size were discussed. The results showed that the fillet weld zone was mainly composed of ferrite and bainite when the material of the sleeve pipe was Q345B. Furthermore, the sleeve pipe’s HAZ (heat affected zone) was dominated by lath martensite, lath bainite, and granular bainite. Moreover, granular bainite and a small amount of ferrite were found in the HAZ of the X80 pipe. It was found that, as the fillet weld size increased, the welding residual stress distribution became more uniform. The hoop stress at weld toe reduced from ~860 MPa of case A to ~680 MPa of case E, and the axial stress at weld toe reduced from ~440 MPa of case A to ~380 MPa of case E. From the viewpoint of welding residual stress, fillet weld size was suggested to be larger than 1.4T. The stress concentration and the stress distribution showed a correlation with the cracking behavior. Weld re-solidification ripples on the weld surface and weld ripples between welding passes or near the weld toe could cause stress concentration and the corresponding crack initiation. Furthermore, when the material of the sleeve pipe changed from Q345B to X80, the high-level tensile stress zone was found to be enlarged. The hoop stress at weld toe increased from ~750 to ~800 MPa, and the axial stress at weld toe increased from ~500 to ~600 MPa. After implementing the new sleeve repair welding process where X80 replaces the material of sleeve pipe, the cracking risk in sleeve pipe will improve. From the perspective of the welding residual stress, it was concluded that the fillet weld size reduction and the sleeve material strength improvement are harmful to in-service welded structures’ safety and integrity. Full article

(This article belongs to the Topic Metallurgical and Materials Engineering)

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18 pages, 30733 KiB

Open AccessArticle

The Friction of Structurally Modified Isotactic Polypropylene

by Natalia Wierzbicka, Tomasz Sterzyński and Marek Nowicki

Materials 2021, 14(23), 7462; https://doi.org/10.3390/ma14237462 - 5 Dec 2021

Cited by 4 | Viewed by 2535

Abstract

The purpose of studies was to analyse an impact of heterogeneous nucleation of modified isotactic polypropylene (iPP) on its tribological properties. The iPP injection molded samples, produced by mold temperature of 20 and 70 °C, were modified with compositions of two nucleating agents [...] Read more.

The purpose of studies was to analyse an impact of heterogeneous nucleation of modified isotactic polypropylene (iPP) on its tribological properties. The iPP injection molded samples, produced by mold temperature of 20 and 70 °C, were modified with compositions of two nucleating agents (NA’s), DMDBS creating α-form and mixture of pimelic acid with calcium stearate (PACS) forming β–phase of iPP, with a total content 0.2 wt.% of NA’s. A polymorphic character of iPP, with both, monoclinic (α) and pseudo-hexagonal (β) crystalline structures, depending on the NA’s ratio, was verified. The morphology observation, DSC, hardness and tribological measurements as test in reciprocating motion with “pin on flat” method, were realized, followed by microscopic observation (confocal and SEM) of the friction patch track. It was found that Shore hardness rises along with DMBDS content, independent on mold temperature. The friction coefficient (COF) depends on NA’s content and forming temperature—for upper mold temperature (70 °C), its value is higher and more divergently related to NA’s composition, what is not the case by 20 °C mold temperature. The height of friction scratches and the width of patch tracks due to its plastic deformation, as detected by confocal microscopy, are related to heterogeneous nucleation modified structure of iPP. Full article

(This article belongs to the Special Issue Structure–Physical Properties Relationship of Polymer and its Composites)

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12 pages, 2682 KiB

Open AccessArticle

Strengthening Mechanism and Carbide Precipitation Behavior of Nb-Mo Microalloy Medium Mn Steel

by Chunquan Liu, Fen Xiong, Yong Wang, Yuxin Cao, Xinbin Liu, Zhengliang Xue, Qichun Peng and Longsheng Peng

Materials 2021, 14(23), 7461; https://doi.org/10.3390/ma14237461 - 5 Dec 2021

Cited by 8 | Viewed by 2178

Abstract

This study investigates the strengthening mechanism and carbide precipitation behavior of medium Mn steel with Nb-Mo microalloy after cyclic quenching and austenite reverse transformation treatment. The results show that the Nb/Mo element not only precipitates (Nb,Mo)C in the grains, hindering the movement of [...] Read more.

This study investigates the strengthening mechanism and carbide precipitation behavior of medium Mn steel with Nb-Mo microalloy after cyclic quenching and austenite reverse transformation treatment. The results show that the Nb/Mo element not only precipitates (Nb,Mo)C in the grains, hindering the movement of dislocations and increases the strength, but also segregates at the austenite/ferrite grain boundary, thus delaying the transformation from austenite to ferrite. In addition, a large amount of nano-scale cementite is retained after cyclic quenching and austenite reverse transformation, which has a positive effect on the proportion of retained austenite in medium Mn steel. Moreover, the carbides with small size and low Mn content are dissolved, and the decomposed C and Mn content are beneficial to the nucleation of austenite during the intercritical annealing process at a temperature of 690 °C. Full article

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14 pages, 3226 KiB

Open AccessArticle

Study on Strength, Water Stability, Shrinkage, and Microstructure of CFB Slag Modified Cement Stabilized Clay

by Mingkai Zhou, Xinyue Liu, Xiao Chen and Peng Gao

Materials 2021, 14(23), 7460; https://doi.org/10.3390/ma14237460 - 5 Dec 2021

Cited by 6 | Viewed by 1941

Abstract

Circulating fluidized bed slag (CFBS) is an industrial waste produced by coal combustion in power plants. To explore the application of CFB slag in cement-stabilized bases, this paper studies the influence of different dosage of CFBS on the mechanics, water stability, and shrinkage [...] Read more.

Circulating fluidized bed slag (CFBS) is an industrial waste produced by coal combustion in power plants. To explore the application of CFB slag in cement-stabilized bases, this paper studies the influence of different dosage of CFBS on the mechanics, water stability, and shrinkage of cement-stabilized soil using laboratory experiments. The hydration activity and interface morphology of CFBS in cement-stabilized clay were observed using XRD and SEM. The improvement mechanism of CFBS on the performance of cement-stabilized clay was revealed. The results indicated that, compared with cement-stabilized clay, cement–CFBS-stabilized clay exhibited better mechanical and water stability, and significantly inhibited the shrinkage deformation of cement-stabilized clay. When the addition of CFBS was 70%, cement–CFBS-stabilized clay had the best mechanics and durability. Microscopic tests show that CFBS contains more active silicon aluminum oxide, which is easily dissolved and the hydration of which produces more gel products, so the mixture structure is denser, the strength is improved, and water does not easily evaporate; it has the characteristics of micro expansion which compensates for dry shrinkage deformation. Full article

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