Materials

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8 pages, 2268 KiB

Open AccessArticle

Thermal Conductivity of Composite Materials Copper-Fullerene Soot

by Tatiana Koltsova, Elizaveta Bobrynina, Aleksei Vozniakovskii, Tatiana Larionova and Olga Klimova-Korsmik

Materials 2022, 15(4), 1415; https://doi.org/10.3390/ma15041415 - 14 Feb 2022

Cited by 6 | Viewed by 1822

Abstract

Copper-based composites strengthened with fullerene soot nanoparticles of 20–30 nm size in concentration up to 23 vol.% were prepared via two methods: mechanical mixing and molecular level mixing. The dependence of thermal conductivity on the carbon concentration was studied. Maxwell’s model describes well [...] Read more.

Copper-based composites strengthened with fullerene soot nanoparticles of 20–30 nm size in concentration up to 23 vol.% were prepared via two methods: mechanical mixing and molecular level mixing. The dependence of thermal conductivity on the carbon concentration was studied. Maxwell’s model describes well the change in the thermal conductivity of the composite obtained by molecular level mixing. However, thermal conductivity of the composite produced by mechanical mixing is significantly lower than the calculated values, due to structural inhomogeneity and residual stresses. Comparison of the thermal conductivity of Cu-fullerene soot composites with that of Cu-based composites described in the literature showed that the prepared materials are not inferior in thermal conductivity to composites containing carbon nanotubes, despite the fact that fullerene soot has a much lower thermal conductivity. Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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11 pages, 3321 KiB

Open AccessArticle

Microstructure Evolution of FeNiCoCrAl_1.3Mo_0.5 High Entropy Alloy during Powder Preparation, Laser Powder Bed Fusion, and Microplasma Spraying

by Anton Semikolenov, Pavel Kuznetsov, Tatyana Bobkova, Svetlana Shalnova, Olga Klimova-Korsmik, Viktor Klinkov, Ilya Kobykhno, Tatyana Larionova and Oleg Tolochko

Materials 2021, 14(24), 7870; https://doi.org/10.3390/ma14247870 - 19 Dec 2021

Cited by 4 | Viewed by 2361

Abstract

In the present study, powder of FeCoCrNiMo_0.5Al_1.3 HEA was manufactured by gas atomization process, and then used for laser powder bed fusion (L-PBF) and microplasma spraying (MPS) technologies. The processes of phase composition and microstructure transformation during above mentioned processes [...] Read more.

In the present study, powder of FeCoCrNiMo_0.5Al_1.3 HEA was manufactured by gas atomization process, and then used for laser powder bed fusion (L-PBF) and microplasma spraying (MPS) technologies. The processes of phase composition and microstructure transformation during above mentioned processes and subsequent heat treatment were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and differential thermal analysis (DTA) methods. It was found that gas atomization leads to a formation of dendrites of body centered cubic (BCC) supersaturated solid solution with insignificant Mo-rich segregations on the peripheries of the dendrites. Annealing leads to an increase of element segregations till to decomposition of the BCC solid solution and formation of σ-phase and B2 phase. Microstructure and phase composition of L-PBF sample are very similar to those of the powder. The MPS coating has a little fraction of face centered cubic (FCC) phase because of Al oxidation during spraying and formation of regions depleted in Al, in which FCC structure becomes more stable. Maximum hardness (950 HV) is achieved in the powder and L-PBF samples after annealing at 600 °C. Elastic modulus of the L-PBF sample, determined by nanoindentation, is 165 GPa, that is 12% lower than that of the cast alloy (186 GPa). Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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11 pages, 6901 KiB

Open AccessArticle

Tribological Properties of Al-Based Composites Reinforced with Fullerene Soot

by Firuz Yunusov, Tatiana V. Larionova, Oleg Tolochko and Alexander D. Breki

Materials 2021, 14(21), 6438; https://doi.org/10.3390/ma14216438 - 27 Oct 2021

Cited by 3 | Viewed by 1451

Abstract

Aluminum-based composite materials reinforced with fullerene soot, which is a mixture of fullerene and amorphous carbon, are promising materials for friction and wear applications. Composite materials: aluminum with 2% fullerene soot (f.s) and Al with 2% f.s and 2% Cu were obtained via [...] Read more.

Aluminum-based composite materials reinforced with fullerene soot, which is a mixture of fullerene and amorphous carbon, are promising materials for friction and wear applications. Composite materials: aluminum with 2% fullerene soot (f.s) and Al with 2% f.s and 2% Cu were obtained via mechanical milling followed by hot pressing. The tribological properties (friction and wear) of the listed composites were investigated and compared with the results for pure aluminum obtained under similar conditions. It has been shown that the addition of fullerene soot reduces the friction coefficient by 25%. At additional alloying with copper, the friction coefficient decreased by 35% in comparison with pure aluminum and also lad to a decrease in friction fluctuations. The wear rate of composite Al with 2% f.s decreased twice in comparison with that of pure aluminum, and with additional alloying it decreased 2.5 times. The morphology of the wear surfaces was investigated by scanning electron microscopy (SEM). The influence of fullerene soot and additional alloying on the wear mechanism was shown. Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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15 pages, 4342 KiB

Open AccessArticle

Load-Bearing Capacity of Beams Reinforced with Composite Rebar in Regard to Existing Guidelines

by Norbert Olczyk, Jarosław Błyszko and Mateusz Techman

Materials 2021, 14(20), 6116; https://doi.org/10.3390/ma14206116 - 15 Oct 2021

Cited by 1 | Viewed by 2287

Abstract

Non-metallic reinforcement such as fiber-reinforced polymer (FRP) is now being increasingly used in construction. Despite numerous similarities, elements reinforced with non-metallic bars work differently from the ones reinforced with steel bars, including cracking and failure mode. The examination of the stress state in [...] Read more.

Non-metallic reinforcement such as fiber-reinforced polymer (FRP) is now being increasingly used in construction. Despite numerous similarities, elements reinforced with non-metallic bars work differently from the ones reinforced with steel bars, including cracking and failure mode. The examination of the stress state in these elements, so important for their proper design, raises many difficulties. The article presents the results of tests of bended beams reinforced with GFRP bars. The results of the experimental tests were compared with calculations based on selected design instructions. The results have shown that beams reinforced with GFRP exhibit increased cracking, higher deflection, and often mode of failure through crushing of concrete. The results have shown that in bended elements reinforced with the GFRP bars, the rebar often does not achieve the strength declared by the manufacturer. The study has shown that theoretical values of load-bearing capacity of beams reinforced with composite rebar differ greatly between different guidelines and instruction. The analysis showed that the use of GFRP bars as a replacement for steel bars is possible in demanding environmental conditions. However, excessive deflections and cracks may result in limited application due to overall serviceability requirements of the element. Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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11 pages, 4283 KiB

Open AccessArticle

Numerical Study on the Effect of Pre-Strain on Detwinning in Rolled Mg Alloy AZ31

by Chao Ma, Xing Duan, Xiaoqian Guo, Hua Qiao, Lianying Zhang and Peidong Wu

Materials 2021, 14(20), 6069; https://doi.org/10.3390/ma14206069 - 14 Oct 2021

Cited by 3 | Viewed by 1234

Abstract

The deformation behavior of rolled Mg alloy AZ31, previously compressed along the rolling direction (RD), was numerically investigated under reverse tension. The EVPSC-TDT model was employed to study the effect of pre-strain on detwinning for 3%, 6% and 9% pre-compressed materials along the [...] Read more.

The deformation behavior of rolled Mg alloy AZ31, previously compressed along the rolling direction (RD), was numerically investigated under reverse tension. The EVPSC-TDT model was employed to study the effect of pre-strain on detwinning for 3%, 6% and 9% pre-compressed materials along the RD. A new criterion was proposed to control the exhaustion of detwinning under reverse tension. Numerical results show good agreement with the corresponding experimental data. It was demonstrated that the proposed criteria can capture the key features associated with detwinning in pre-compressed materials. Regardless of the amount of pre-compression, detwinning is activated under reverse tension, leading to low yield stress and a typical s-shaped flow curve. The inflection point reflects the exhaustion of detwinning, which is delayed when increasing the amount of pre-compression. Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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7 pages, 21126 KiB

Open AccessArticle

Electrodeposition and Corrosion Properties of Nickel–Graphene Oxide Composite Coatings

by Vitaly Tseluikin, Asel Dzhumieva, Andrey Yakovlev, Anton Mostovoy, Svetlana Zakirova, Anastasia Strilets and Marina Lopukhova

Materials 2021, 14(19), 5624; https://doi.org/10.3390/ma14195624 - 27 Sep 2021

Cited by 2 | Viewed by 2135

Abstract

Nickel-based composite electrochemical coatings (CEC) modified with multilayer graphene oxide (GO) were obtained from a sulfate-chloride electrolyte in the reverse electrolysis mode. The microstructure of these CECs was investigated by X-ray phase analysis and scanning electron microscopy. The corrosion-electrochemical behavior of nickel–GO composite [...] Read more.

Nickel-based composite electrochemical coatings (CEC) modified with multilayer graphene oxide (GO) were obtained from a sulfate-chloride electrolyte in the reverse electrolysis mode. The microstructure of these CECs was investigated by X-ray phase analysis and scanning electron microscopy. The corrosion-electrochemical behavior of nickel–GO composite coatings in a 0.5 M solution of H₂SO₄was studied. Tests in a 3.5% NaCl solution showed that the inclusion of GO particles into the composition of electrolytic nickel deposits makes their corrosion rate 1.40–1.50 times less. Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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12 pages, 8373 KiB

Open AccessArticle

Fabrication of Ring-Shaped Deposits of Polystyrene Microparticles Driven by Thermocapillary Mechanism

by Mohammed Al-Muzaiqer, Natalia Ivanova and Denis Klyuev

Materials 2021, 14(18), 5267; https://doi.org/10.3390/ma14185267 - 13 Sep 2021

Cited by 2 | Viewed by 1733

Abstract

Fabrication of ring-shaped deposits of microparticles on solid surfaces with the desired length scales and morphology of particle arrangements is of great importance when developing modern optical and electronic resonators, chemical sensors, touch screens, field-emission displays, porous materials, and coatings with various functional [...] Read more.

Fabrication of ring-shaped deposits of microparticles on solid surfaces with the desired length scales and morphology of particle arrangements is of great importance when developing modern optical and electronic resonators, chemical sensors, touch screens, field-emission displays, porous materials, and coatings with various functional properties. However, the controlled formation of ring-shaped patterns scaling from a few millimeters up to centimeters with simultaneous control of particle arrangement at the microscale is one of the most challenging problems in advanced materials science and technology. Here, we report a fabrication approach for ring-shaped structures of microparticles on a glass surface that relied on a local thermal impact produced by the subsurface heater and heat sink. Thermocapillary convection in the liquid covering microparticles in combination with evaporative lithography is responsible for the particle transport and the assembling into the ring-shaped patterns. An advantageous feature of this approach is based on the control of thermocapillary flow direction, achieved by changing the sign of the temperature gradient in the liquid, switching between heating and cooling modes. That allows for changing the particle transfer direction to create the ring-shaped deposits and dynamically tune their size and density distribution. We have studied the influence of the power applied to the heat source/sink and the duration of the applied thermal field on the rate of the ring fabrication, the sizes of the ring and the profile of the particle distribution in the ring. The proposed method is flexible to control simultaneously the centimeter scale and microscale processes of transfer and arrangements of particles and can be applied to the fabrication of ring structures of particles of different nature and shape. Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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18 pages, 3077 KiB

Open AccessArticle

Modification of Mechanical Properties in Directed Energy Deposition by a Static Magnetic Field: Experimental and Theoretical Analysis

by Aleksandr M. Filimonov, Oleg A. Rogozin, Oleg N. Dubinin, Yulia O. Kuzminova, Anastasia A. Shibalova, Ilya V. Okulov, Iskander S. Akhatov and Stanislav A. Evlashin

Materials 2021, 14(18), 5190; https://doi.org/10.3390/ma14185190 - 9 Sep 2021

Cited by 8 | Viewed by 2376

Abstract

The superimposed magnetic field affects the microstructure and mechanical properties of additively manufactured metal parts. In this work, the samples were fabricated from Inconel 718 superalloy by directed energy deposition under a 0.2 T static field. The magnetohydrodynamic 1D model is proposed for [...] Read more.

The superimposed magnetic field affects the microstructure and mechanical properties of additively manufactured metal parts. In this work, the samples were fabricated from Inconel 718 superalloy by directed energy deposition under a 0.2 T static field. The magnetohydrodynamic 1D model is proposed for the estimation of a fluid flow inside a molten pool. According to the theoretical predictions, the fluid flow is slightly decreased by an applied field. The estimated thermoelectric magnetic convection in the mushy zone is shown to be negligible to change in subgrain size, but enough to reduce the hard-to-dissolve Nb-rich phase, thereby improving the average ultimate elongation from 23% to 27%. The obtained results confirm that an external static magnetic field can modify and enhance the mechanical properties of additively manufactured materials. Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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10 pages, 2693 KiB

Open AccessArticle

The Features of Martensitic Transformation in 12% Chromium Ferritic–Martensitic Steels

by Kseniya Bazaleeva, Alexander Golubnichiy, Anton Chernov, Andrey Ni and Ruslan Mendagaliyev

Materials 2021, 14(16), 4503; https://doi.org/10.3390/ma14164503 - 11 Aug 2021

Viewed by 2019

Abstract

An anomaly in martensitic transformation (the effect of martensitic two-peak splitting in the temperature-dependent thermal expansion coefficient) in complex alloyed 12% chromium steels Fe-12%Cr-Ni-Mo-W-Nb-V-B (ChS-139), Fe-12%Cr-Mo-W-Si-Nb-V (EP-823) and Fe-12%Cr-2%W-V-Ta-B (EK-181) was investigated in this study. This effect is manifested in steels with a [...] Read more.

An anomaly in martensitic transformation (the effect of martensitic two-peak splitting in the temperature-dependent thermal expansion coefficient) in complex alloyed 12% chromium steels Fe-12%Cr-Ni-Mo-W-Nb-V-B (ChS-139), Fe-12%Cr-Mo-W-Si-Nb-V (EP-823) and Fe-12%Cr-2%W-V-Ta-B (EK-181) was investigated in this study. This effect is manifested in steels with a higher degree of alloying (ChS-139). During varying temperature regimes in dilatometric analysis, it was found that the splitting of the martensitic peak was associated with the superposition of two martensitic transformations of austenite depleted and enriched with alloying elements. The anomaly was subsequently eliminated by homogenization of the steel composition due to high-temperature aging in the γ-region. It was shown that if steel is heated to 900 °C, which lies in the (α + γ) phase region or slightly higher during cooling, then the decomposition of austenite proceeds in two stages: during the first stage, austenite is diffused into ferrite with carbides; during the second stage, shear transformation of austenite to martensite occurs. Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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12 pages, 3429 KiB

Open AccessArticle

Structural Factors Inducing Cracking of Brass Fittings

by Lenka Kunčická, Michal Jambor, Adam Weiser and Jiří Dvořák

Materials 2021, 14(12), 3255; https://doi.org/10.3390/ma14123255 - 12 Jun 2021

Cited by 6 | Viewed by 2003

Abstract

Cu–Zn–Pb brasses are popular materials, from which numerous industrially and commercially used components are fabricated. These alloys are typically subjected to multiple-step processing—involving casting, extrusion, hot forming, and machining—which can introduce various defects to the final product. The present study focuses on the [...] Read more.

Cu–Zn–Pb brasses are popular materials, from which numerous industrially and commercially used components are fabricated. These alloys are typically subjected to multiple-step processing—involving casting, extrusion, hot forming, and machining—which can introduce various defects to the final product. The present study focuses on the detailed characterization of the structure of a brass fitting—i.e., a pre-shaped medical gas valve, produced by hot die forging—and attempts to assess the factors beyond local cracking occurring during processing. The analyses involved characterization of plastic flow via optical microscopy, and investigations of the phenomena in the vicinity of the crack, for which we used scanning and transmission electron microscopy. Numerical simulation was implemented not only to characterize the plastic flow more in detail, but primarily to investigate the probability of the occurrence of cracking based on the presence of stress. Last, but not least, microhardness in specific locations of the fitting were examined. The results reveal that the cracking occurring in the location with the highest probability of the occurrence of defects was most likely induced by differences in the chemical composition; the location the crack in which developed exhibited local changes not only in chemical composition—which manifested as the presence of brittle precipitates—but also in beta phase depletion. Moreover, as a result of the presence of oxidic precipitates and the hard and brittle alpha phase, the vicinity of the crack exhibited an increase in microhardness, which contributed to local brittleness. Full article

(This article belongs to the Special Issue Structure, Properties and Application of Metal and Composite Materials in Various Industries)

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