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  • National University of Science and Technology MISiS  (9)
  • 2020-2024  (9)
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  • National University of Science and Technology MISiS  (9)
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  • 2020-2024  (9)
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  • 1
    Online Resource
    Online Resource
    Structural phase variations in high-entropy alloy at irradiation by pulsed electron beam
    National University of Science and Technology MISiS ; 2021
    In:  Izvestiya. Ferrous Metallurgy Vol. 64, No. 11 ( 2021-12-10), p. 846-854
    Details
    In: Izvestiya. Ferrous Metallurgy, National University of Science and Technology MISiS, Vol. 64, No. 11 ( 2021-12-10), p. 846-854
    Abstract: The high-entropy alloy (HEA) of Al - Co - Cr - Fe - Ni system of nonequiatomic composition is obtained by the technology of wire-arc additive manufacturing (WAAM) in atmosphere of pure nitrogen. By the methods of modern physical materials science it is shown that in the initial state the alloy has dendritic structure indicating nonhomogeneous distribution of alloying elements. It is a multiphase material whose main phases are Al 3 NCr 3 C 2 , (Ni, Co) 3 Al 4 . Nonadimensional particles (Ni, Co) 3 Al 4 of cubic shape are located along interfaces of submicron phases Al3Ni and Cr 3 C 2 . The HEA irradiation by pulsed electron beams with energy density E s = 10 + 30 J/cm 2 , pulse duration of 50 is, frequency of 3 Hz and pulse number of 3 leads to high-velocity melting and subsequent crystallization of surface layer. If E s = 10 J/cm 2 , no failure of dendritic crystallization structure happens. Interdendritic spaces are enriched in chemical elements Al, Ni and Fe, and dendrites themselves - in chromium atoms. The most liquating element of the alloy is Al, the least one is Co. If E s = 20 J/cm 2 , a nanocrystalline structure is formed in the layer 15 inn thick in bulk of grains. Size of crystallization cells amounts to 100 - 200 nm, size of inclusions in cell junctions is 20 - 25 nm, and along cell boundaries it is 10 - 15 nm. Cells of high-velocity crystallization are enriched in Al and Ni. The Co atoms are homogeneously distributed along the surface layer volume. The most liquating element is Cr, the least liquating one is Co. The increase in energy density of electron beam to 30 J/cm 2 doesn't lead to substantial (as compared to E s = 20 J/cm 2 ) variations in surface layer structure. The irradiation mode ( E s = 20 J/cm 2 , 50 is, 3 pulses, 0.3 Hz) is detected that allows formation of the surface layer with the highest level of homogeneity of chemical element distribution in the alloy.
    Type of Medium: Online Resource
    ISSN: 2410-2091 , 0368-0797
    URL: Article
    DOI: 10.17073/0368-0797-2021-11-846-854
    Language: Unknown
    Publisher: National University of Science and Technology MISiS
    Publication Date: 2021
    SSG: 19,1
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Effect of hafnium on cast microstructure in alloy 1570
    National University of Science and Technology MISiS ; 2023
    In:  Izvestiya. Non-Ferrous Metallurgy Vol. 1, No. 1 ( 2023-02-19), p. 56-65
    Details
    In: Izvestiya. Non-Ferrous Metallurgy, National University of Science and Technology MISiS, Vol. 1, No. 1 ( 2023-02-19), p. 56-65
    Abstract: The issue is devoted to the study of the influence of hafnium on the structure and properties of alloy 1570. Ingots from alloy 1570 were cast into the steel coquille, including those with additives of hafnium 0.1, 0.2 and 0.5 %. To determine the size of the grain structure in the obtained ingots, an Axionovert-40 MAT optical microscope was used, chemical analysis of intermetallic particles was carried out using JEOL 6390A SEM. In addition, for the alloy 1570 and 1570–0.5Hf, the presence of nanoparticles with the L12 structure was studied using transmission electron microscope JEM-2100. Studies showed that hafnium additives make it possible to achieve a significant modification of the cast structure. For example, when introducing hafnium into the initial alloy in an amount of 0.5 % of the total weight, it was possible to achieve a reduction in the average grain size by 2 times. Scanning microscopy data showed that hafnium partially dissolves in particles containing scandium and zirconium as well. The addition of hafnium increases the number of large particles formed during crystallization. Transmission microscopy showed the presence of coherent aluminum matrix nanoparticles in alloy 1570 and having a superstructure of L12, which were most likely formed during intermittent decay during ingot cooling. When 0.5 % Hf was added, no nanoparticles with the L12 superstructure were detected. To explain the latter fact, it is necessary to study the surface of the liquidus of the Al–Hf–Sc system, as well as to study the effect of hafnium on the diffusion coefficient of scandium in aluminum.
    Type of Medium: Online Resource
    ISSN: 2412-8783 , 0021-3438
    URL: Article
    DOI: 10.17073/0021-3438-2023-1-56-65
    Language: Unknown
    Publisher: National University of Science and Technology MISiS
    Publication Date: 2023
    SSG: 19,1
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Generation of increased mechanical properties of Cantor high­entropy alloy
    National University of Science and Technology MISiS ; 2021
    In:  Izvestiya. Ferrous Metallurgy Vol. 64, No. 8 ( 2021-09-02), p. 599-605
    Details
    In: Izvestiya. Ferrous Metallurgy, National University of Science and Technology MISiS, Vol. 64, No. 8 ( 2021-09-02), p. 599-605
    Abstract: The article considers a brief review of the last years of Russian and foreign research on the possibilities of improving mechanical properties of the Cantor quinary high­entropy alloy (HEA) with different phase composition in wide temperature range. The alloy, one of the frst created equimolar HEAs with FCC structure, needs mechanical properties improvement in accordance with possible felds of application in spite of its high impact toughness and increased creep resistance. It has been noted that bimodal distribution of the grains by sizes under severe plastic torsional strain at high pressure of 7.8 GPa of cast alloy and subsequent short­time annealing at 873 and 973 K can change strength and plastic properties. Nanodimensional scale of the grains surrounded by amorphous envelope has been obtained for HEA produced by the method of magnetron sputtering and subsequent annealing at 573 K. In such a two­phase alloy nanohardness amounted to 9.44 GPa and elasticity modulus – to 183 GPa. Using plasticity effect induced by phase transformation in (CrMnFeCoNi)50Fe50 alloy obtained by the method of laser additive technology the ultimate strength of 415 – 470 MPa has been reached at high level of plasticity up to 77 %. It has been ensured by FCC → BCC diffusionless transformation. It is shown that difference in mechanisms of plastic strain of cast alloy at 77 K and 293 K (dislocation glide and twinning) determines a combination of increased “strength­plasticity” properties. Samples for generation of twins prestrained at 77 K exhibit increased strength and plasticity under subsequent loading at 293 K in comparison with the unstrained ones. For HEA obtained by laser additive technology this way of increasing properties is also true. The way of improving mechanical properties at the expense of electron beam processing is noted. The attention is paid to the necessity of taking into account the role of entropy, crystal lattice distortions, short­range order, weak diffusion and “cocktail” effect in the analysis of mechanical properties.
    Type of Medium: Online Resource
    ISSN: 2410-2091 , 0368-0797
    URL: Article
    DOI: 10.17073/0368-0797-2021-8-599-605
    Language: Unknown
    Publisher: National University of Science and Technology MISiS
    Publication Date: 2021
    SSG: 19,1
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Application of high-entropy alloys
    National University of Science and Technology MISiS ; 2021
    In:  Izvestiya. Ferrous Metallurgy Vol. 64, No. 10 ( 2021-11-24), p. 747-754
    Details
    In: Izvestiya. Ferrous Metallurgy, National University of Science and Technology MISiS, Vol. 64, No. 10 ( 2021-11-24), p. 747-754
    Abstract: From accumulated information on structure, properties, stability, and methods of manufacturing the high-entropy alloys (HEA) created early in the 21 century it follows that they possess a whole complex of useful properties that suggests their perspective application in different branches of industry. The authors have made a short review of scientific articles on analysis of possibilities of HEA application in specific science-consuming branches of the last 5 years. In biomedicine the protective coatings made of (TiZrNbHfTa)N and (TiZrNbHfTa)O HEAs possess biocompatibility, high level of mechanical properties, high wear- and corrosion resistance in physiological media, and excellent adhesion. Products made of (MoTa) χ NbTiZr passed clinical tests successfully when being implanted to living muscular tissue. The developed HEAs based on rare-earth elements and metals of Fe group such as YbTbDyAl Me ( Me = Fe, Co, Ni) possess magnetocaloric effect, have Curie temperature close to room one and may be used in modern refrigerator mechanisms. Changing in stoichiometric composition of CoCrFeNiTi HEAs, alloying them and performing thermal treatment, the researchers succeed in obtaining soft magnetic materials. Fields of HEA application are presented as following: catalysts of ammonia oxidation - (PtPdRhRuCe), ammonia decomposition - (RuRhCoNiIr), oxidation of aromatic alcohols - (Co 0,2 Ni 0,2 Cu 0,2 Mg 0,2 Zn 0,2 ), electric catalysts of hydrogen extraction - (Ni 20 Fe 20 Mo 10 Cr 15 Co 35 ), redox reactions (AlCuNiPtMn and AlNiCuPtPdAu), and oxidation of methanol/ethanol. HEAs can be used as electrodes - anodes and cathodes for Li-ion and Na-ion accumulators. Synthesized nanoporous HEA AlCoCrFeNi has high bulk density up to 700 F/cm 3 and cyclic stability ( 〉 3000 cycles) and is used in supercapacitors. High-entropy oxides such as (MgNiCoCuZn) 0.95 Li 0.05 O with high dielectric properties in a wide frequency range may be used in electronic converters. Examples of HEA application are given: as coatings of ship parts being operated in sea water, various welded joints, parts of nuclear reactors. Perspectives of widening the fields of HEA application are indicated.
    Type of Medium: Online Resource
    ISSN: 2410-2091 , 0368-0797
    URL: Article
    DOI: 10.17073/0368-0797-2021-10-747-754
    Language: Unknown
    Publisher: National University of Science and Technology MISiS
    Publication Date: 2021
    SSG: 19,1
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    Online Resource
  • 5
    Online Resource
    Online Resource
    Deformation behavior of high-entropy alloy system Al – Co – Cr – Fe – Ni achieved by wire-arc additive manufacturing
    National University of Science and Technology MISiS ; 2021
    In:  Izvestiya. Ferrous Metallurgy Vol. 64, No. 1 ( 2021-02-16), p. 68-74
    Details
    In: Izvestiya. Ferrous Metallurgy, National University of Science and Technology MISiS, Vol. 64, No. 1 ( 2021-02-16), p. 68-74
    Abstract: A non-equiatomic high-entropy alloy (HEA) of the Al – Co – Cr – Fe – Ni system was obtained using wire-arc additive manufacturing technology in the atmosphere of pure argon. The initial wire had 3 conductors with different chemical composition: pure aluminum wire (Al ≈ 99.95 %), chromium-nickel wire (Cr ≈ 20 %, Ni ≈ 80 %), and cobalt alloy wire (Co ≈ 17 %, Fe ≈ 54 %, Ni ≈ 29 %). The resulting sample of high-entropy alloy was a parallelepiped consisting of 20 deposited layers in height and 4 layers in thickness. The alloy had the following elemental composition, detected by energy-dispersive X-ray spectroscopy: aluminum (35.67 ± 1.34 at. %), nickel (33.79 ± 0.46 at. %), iron (17.28 ± 1.83 at. %), chromium (8.28 ± 0.15 at. %) and cobalt (4.99 ± 0.09 at. %). Scanning electron microscopy revealed that the source material has a dendritic structure and contains particles of the second phase at grain boundaries. Element distribution maps obtained by mapping methods have shown that grain volumes are enriched in aluminum and nickel, while grain boundaries contain chromium and iron. Cobalt is distributed in the crystal lattice of the resulting HEA quasi-uniformly. It is shown that during tensile tests, the material was destroyed by the mechanism of intra-grain cleavage. The formation of brittle cracks along the boundaries and at the junctions of grain boundaries, i.e., in places containing inclusions of the second phases, is revealed. It was suggested that one of the reasons for the increased fragility of HEA, produced by wire-arc additive manufacturing, is revealed uneven distribution of elements in microstructure of the alloy and also the presence in material volume of discontinuities of various shapes and sizes.
    Type of Medium: Online Resource
    ISSN: 2410-2091 , 0368-0797
    URL: Article
    DOI: 10.17073/0368-0797-2021-1-68-74
    Language: Unknown
    Publisher: National University of Science and Technology MISiS
    Publication Date: 2021
    SSG: 19,1
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  • 6
    Online Resource
    Online Resource
    Control of mechanical properties of a high-entropy alloy Cantor CoCrFeMnNi
    National University of Science and Technology MISiS ; 2022
    In:  Izvestiya. Ferrous Metallurgy Vol. 65, No. 8 ( 2022-09-01), p. 563-572
    Details
    In: Izvestiya. Ferrous Metallurgy, National University of Science and Technology MISiS, Vol. 65, No. 8 ( 2022-09-01), p. 563-572
    Abstract: A brief analysis of the work on changing the mechanical properties of the high-energy alloy (HEA) Cantor CoCrFeMnNi in various ways has been performed. The article describes the influence of alloying with aluminum, vanadium, manganese, titanium, silicon, carbon, copper on the hardening of wind turbines obtained by vacuum arc melting, laser melting, arc melting and drip casting, mechanical alloying with subsequent plasma sintering, gas sputtering followed by shock wave and static compaction. It is shown that additives of 2.5 % TiC and 5 % WC significantly improve the tensile strength, but reduce the elongation to failure. The effect of grain size in the range of 4.4 – 155 µm is to increase the tensile strength with a decrease in grain size. Lowering the temperature increases the strength and yield limits for grains of all sizes. Intensive plastic deformation forming nanoscale (~50 nm) grains significantly increases the tensile strength up to 1950 MPa and hardness up to 520 HV. Subsequent isochronous and isothermal annealing allows varying the strength and ductility of wind turbines. The formation of nanostructured-phase states during shock compounding, mechanical alloying and subsequent spark plasma formation significantly increase the tensile strength at room temperature, maintaining excellent plasticity (elongation of approximately 28 %). As one of the methods of modifying the mechanical properties of wind turbines, the authors propose electron-beam processing (EPO). The analysis of the deformation curves of the wind turbine, obtained by the technology of wire-arc additive production, after EPO with an electron beam energy density of 10 – 30 J/cm 2 , has been carried out; assumptions about the reasons for the decrease in strength and ductility characteristics have been found and substantiated. A comparative analysis of mechanical properties of the Cantor wind turbine obtained by various methods was carried out, and the reasons for discrepancy in the values of strength and plastic parameters were noted.
    Type of Medium: Online Resource
    ISSN: 2410-2091 , 0368-0797
    URL: Article
    DOI: 10.17073/0368-0797-2022-8-563-572
    Language: Unknown
    Publisher: National University of Science and Technology MISiS
    Publication Date: 2022
    SSG: 19,1
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  • 7
    Online Resource
    Online Resource
    Coatings from high-entropy alloys: State and prospects
    National University of Science and Technology MISiS ; 2022
    In:  Izvestiya. Ferrous Metallurgy Vol. 65, No. 10 ( 2022-10-30), p. 683-692
    Details
    In: Izvestiya. Ferrous Metallurgy, National University of Science and Technology MISiS, Vol. 65, No. 10 ( 2022-10-30), p. 683-692
    Abstract: The authors made a brief review of recent publications by foreign and domestic researchers on the structure, phase composition, and properties of films and coatings of five-component high-entropy alloys (HEA) on various substrates and modification of the HEA surface by various types of processing. The main methods of applying films and coatings are considered: magnetron sputtering, thermal sputtering, laser sputtering, and electrodeposition. Particular attention is paid to the deposition of coatings on stainless steels and titanium alloys. The positive change in the tribological, strength properties, and corrosion resistance of film coatings in a wide temperature range is analyzed and possible causes of the observed effects are discussed. The role of solid solution strengthening, formation of fine-grained structure, and the formation of oxide layers enriched with one of the HEA components were taken into account. The authors identified new methods for applying coatings from HEA and subsequent processing. Using Nb and Ti doping as an example, their role in increasing microhardness, wear resistance, and reducing the friction coefficient in coatings were revealed. Electrolytic polishing, electroerosive machining, mechanical polishing and their combination are considered among the methods of HEA surface treatment. A number of works propose a method of powder borating to increase the surface strength and wear resistance of HEAs. The paper considers analysis of works on electron-beam processing as one of the promising and high efficient methods of HEA surface hardening.
    Type of Medium: Online Resource
    ISSN: 2410-2091 , 0368-0797
    URL: Article
    DOI: 10.17073/0368-0797-2022-10-683-692
    Language: Unknown
    Publisher: National University of Science and Technology MISiS
    Publication Date: 2022
    SSG: 19,1
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  • 8
    Online Resource
    Online Resource
    High-entropy alloys: Structure, mechanical properties, deformation mechanisms and application
    National University of Science and Technology MISiS ; 2021
    In:  Izvestiya. Ferrous Metallurgy Vol. 64, No. 4 ( 2021-06-04), p. 249-258
    Details
    In: Izvestiya. Ferrous Metallurgy, National University of Science and Technology MISiS, Vol. 64, No. 4 ( 2021-06-04), p. 249-258
    Abstract: The article considers a brief review of the foreign publications on the study of the structure, phase composition and properties of five-component high-entropy alloys (HEAs) in different structural states in a wide temperature range over the past two decades. HEAs attract the attention of scientists with their unique and unusual properties. The difficulties of comparative analysis and generalization of data are noted due to different methods of obtaining HEAs, modes of mechanical tests for uniaxial compression and tension, sizes and shapes of the samples, types of thermal treatments, and phase composition (bcc and fcc crystal lattices). It is noted that the HEA with a bcc lattice has mainly high strength and low plasticity, and the HEA  with a fcc lattice has low strength and increased plasticity. A significant increase in the properties of the FeMnCoCrNi HEA with a fcc lattice can be achieved by alloying with boron and optimizing the parameters of thermal mechanical treatment at alloying with carbon in the amount of 1 % (at.). The deformation curves analyzed in the temperature range –196 ÷ 800 °C indicate an increase in the yield strength with a decrease in the grain size from 150 to 5 microns. As the temperature decreases, the yield strength and elongation increase. The effect of deformation rate on the mechanical properties is an increase in the ultimate strength and yield strength, which is most noticeable at high rates of 10 –2 ÷ 10 3 s –1 . The features of HEAs deformation behavior in the mono- and poly-crystalline states are noted. The complex of high operational properties of HEAs makes it possible to use them in various industries. There are good prospects of using energy treatment to modify the surface layers and further improve HEAs properties.
    Type of Medium: Online Resource
    ISSN: 2410-2091 , 0368-0797
    URL: Article
    DOI: 10.17073/0368-0797-2021-4-249-258
    Language: Unknown
    Publisher: National University of Science and Technology MISiS
    Publication Date: 2021
    SSG: 19,1
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  • 9
    Online Resource
    Online Resource
    Increase of alloys functional properties by electronic beam processing
    National University of Science and Technology MISiS ; 2021
    In:  Izvestiya. Ferrous Metallurgy Vol. 64, No. 2 ( 2021-04-02), p. 129-134
    Details
    In: Izvestiya. Ferrous Metallurgy, National University of Science and Technology MISiS, Vol. 64, No. 2 ( 2021-04-02), p. 129-134
    Abstract: The article considers a review of domestic and foreign works on the use of intense pulsed electron beams for surface treatment of metals, alloys, cermet and ceramic materials. The advantages of using electron pulsed beams over laser beams, plasma flows, and ion beams are noted. The promising directions of using electron-beam processing were analyzed and are as following: 1 – smoothing the surface, getting rid of surface microcracks, while simultaneously changing the structural-phase state of the surface layer, to create high-performance technologies for the finishing processing of critical metal products of complex shape made of titanium alloy Ti-6Al-4V and titanium; steels of various classes; hard alloy WC – 10 wt. % Сo; aluminum; 2 – removal of microbursts formed during the manufacture of precision molds (SKD11 steel) and biomedical products (Ti-6Al-4V alloy); 3 – finishing the surface of molds and dies; 4 – improvement of the functional properties of metallic biomaterials: stainless steel, titanium and its alloys, alloys based on titanium nickelide with shape memory effect, and magnesium alloys; 5 – processing of medical devices and implants; 6 – formation of the surface alloys for powerful electrodynamic systems; 7 – improvement of the characteristics of aircraft engine and compressor blades; 8 – formation of thermal barrier coatings applied to the surface of the combustion chambers. It is shown that with the correct choice of process parameters, such as accelerating voltage, energy density of electron beam, number of pulses, and pulse duration, it is possible to control carefully and/or manipulate the characteristics of structural-phase state and surface properties. In order to improve the properties of the material and the durability of the products made of it, an important factor is the structure modification to form a submicro-nanosized grain (or subgrain structure).
    Type of Medium: Online Resource
    ISSN: 2410-2091 , 0368-0797
    URL: Article
    DOI: 10.17073/0368-0797-2021-2-129-134
    Language: Unknown
    Publisher: National University of Science and Technology MISiS
    Publication Date: 2021
    SSG: 19,1
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