scholarly journals Structural phase variations in high-entropy alloy at irradiation by pulsed electron beam

2021 ◽  
Vol 64 (11) ◽  
pp. 846-854
Author(s):  
Yu. F. Ivanov ◽  
V. E. Gromov ◽  
S. V. Konovalov ◽  
Yu. A. Shlyarova ◽  
S. V. Vorob'ev
Keyword(s):  
Surface Layer ◽  
Electron Beam ◽  
Energy Density ◽  
High Velocity ◽  
Structural Phase ◽  
Dendritic Structure ◽  
Cell Junctions ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Wire Arc Additive Manufacturing

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 Al3NCr3C2 , (Ni, Co)3Al4 . Nonadimensional particles (Ni, Co)3Al4 of cubic shape are located along interfaces of submicron phases Al3Ni and Cr3C2 . The HEA irradiation by pulsed electron beams with energy density Es = 10 + 30 J/cm2, 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 Es = 10 J/cm2, 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 Es = 20 J/cm2, 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/cm2 doesn't lead to substantial (as compared to Es = 20 J/cm2 ) variations in surface layer structure. The irradiation mode (Es = 20 J/cm2, 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.

scholarly journals Эволюция структуры AlCoCrFeNi высокоэнтропийного сплава при облучении импульсным электронным пучком

2021 ◽  
Vol 91 (12) ◽  
pp. 1971
Author(s):  
Ю.Ф. Иванов ◽  
В.Е. Громов ◽  
С.В. Коновалов ◽  
Ю.А. Шлярова
Keyword(s):  
Materials Science ◽  
Structural Phase ◽  
Dendritic Structure ◽  
High Entropy Alloy ◽  
Second Phase ◽  
Initial State ◽  
High Entropy ◽  
Electron Beam Processing ◽  
Distribution Of Elements ◽  
Physical Materials

By the methods of modern physical materials science the change in structural-phase state of AlCoCrFeNi high-entropy alloy (HEA) of nonequiatomic composition obtained by the methods of wire arc additive technology (WAAM) after irradiation by electron beams with energy density of (10-30) J/cm2, durality of 50 μs, frequency 0.3 Hz is studied. In the initial state the alloy had a dendritic structure indicating the inhomogeneous distribution of elements. It is shown that electron beam processing forms the structure of high-velocity cellular crystallization with cell size of 100-200 nm, along boundaries of which the nanodimensional (15-30 nm) inclusions of the second phase enriched in Cr and Fe atoms are located.

scholarly journals Deformation behavior of high-entropy alloy system Al – Co – Cr – Fe – Ni achieved by wire-arc additive manufacturing

2021 ◽  
Vol 64 (1) ◽  
pp. 68-74
Author(s):  
Yu. F. Ivanov ◽  
K. A. Osintsev ◽  
V. E. Gromov ◽  
S. V. Konovalov ◽  
I. A. Panchenko
Keyword(s):  
Additive Manufacturing ◽  
Grain Boundaries ◽  
Pure Aluminum ◽  
Dendritic Structure ◽  
High Entropy Alloy ◽  
Second Phase ◽  
Nickel Wire ◽  
High Entropy ◽  
Distribution Maps ◽  
Wire Arc Additive Manufacturing

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.

scholarly journals Evolution of Structure in AlCoCrFeNi High-Entropy Alloy Irradiated by a Pulsed Electron Beam

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1228
Author(s):  
Kirill Osintsev ◽  
Victor Gromov ◽  
Yurii Ivanov ◽  
Sergey Konovalov ◽  
Irina Panchenko ◽  
...  
Keyword(s):  
Surface Modification ◽  
Electron Beam ◽  
High Speed ◽  
Chemical Elements ◽  
High Entropy Alloy ◽  
Second Phase ◽  
High Entropy ◽  
Pulsed Electron Beam ◽  
Beam Surface ◽  
Wire Arc Additive Manufacturing

High-current pulsed electron-beam (HCPEB) surface modification of Al-Co-Cr-Fe-Ni high-entropy alloy (wt. %) Al—15.64; Co—7.78; Cr—8.87; Fe—22.31; Ni—44.57, fabricated via wire-arc additive manufacturing was studied. The initial condition of the sample is characterized by a highly inhomogeneous distribution of the chemical elements that form the alloy. The alloy samples were irradiated with the different electron beam energy densities of 10, 20 and 30 J/cm2. The surface structure was then analyzed in relation to an energy deposition mode. The study has established that HCPEB induces a high-speed crystallization structure with cells varying in size from 100 to 200 nm. There are nano-dimensional (15–30 nm) second-phase inclusions enriched with atoms of Cr and Fe along the grain boundaries. The most liquating elements are Cr and Al. Electron beam surface modification of the high-entropy alloy induces its homogenization. The study has highlighted that the mode of 20 J/cm2, 50 µs, 3 pulses, 0.3 s−1 results in the formation of a surface layer with the most homogenously distributed chemical elements.

scholarly journals High-velocity deformation of Al0.3CoCrFeNi high-entropy alloy: Remarkable resistance to shear failure

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Z. Li ◽  
S. Zhao ◽  
H. Diao ◽  
P. K. Liaw ◽  
M. A. Meyers
Keyword(s):  
High Velocity ◽  
Shear Failure ◽  
High Entropy Alloy ◽  
High Entropy

scholarly journals Microstructure and Mechanical Properties of Sintered and Heat-Treated HfNbTaTiZr High Entropy Alloy

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1324 ◽  
Author(s):  
Jaroslav Málek ◽  
Jiří Zýka ◽  
František Lukáč ◽  
Jakub Čížek ◽  
Lenka Kunčická ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Dendritic Structure ◽  
Cold Isostatic Pressing ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Arc Melting ◽  
Powder Metallurgy Process ◽  
Heat Treated ◽  
Near Net Shape ◽  
Metallurgy Process

High entropy alloys (HEAs) have attracted researchers’ interest in recent years. The aim of this work was to prepare the HfNbTaTiZr high entropy alloy via the powder metallurgy process and characterize its properties. The powder metallurgy process is a prospective solution for the synthesis of various alloys and has several advantages over arc melting (e.g., no dendritic structure, near net-shape, etc.). Cold isostatic pressing of blended elemental powders and subsequent sintering at 1400 °C for various time periods up to 64 h was used. Certain residual porosity, as well as bcc2 (Nb- and Ta-rich) and hcp (Zr- and Hf-rich) phases, remained in the bcc microstructure after sintering. The bcc2 phase was completely eliminated during annealing (1200 °C/1h) and subsequent water quenching. The hardness values of the sintered specimens ranged from 300 to 400 HV10. The grain coarsening during sintering was significantly limited and the maximum average grain diameter after 64 h of sintering was approximately 60 μm. The compression strength at 800 °C was 370 MPa and decreased to 47 MPa at 1200 °C. Porosity can be removed during the hot deformation process, leading to an increase in hardness to ~450 HV10.

Surface modification of CrFeCoNiMo high entropy alloy induced by high-current pulsed electron beam

2020 ◽  
Vol 504 ◽  
pp. 144453 ◽  
Author(s):  
Peng Lyu ◽  
Yanan Chen ◽  
Zijian Liu ◽  
Jie Cai ◽  
Conglin Zhang ◽  
...  
Keyword(s):  
Surface Modification ◽  
Electron Beam ◽  
High Entropy Alloy ◽  
High Current ◽  
High Entropy ◽  
Pulsed Electron Beam

Microstructures and Wear Resistance of Al1.5CrFeNiTi0.5 and Al1.5CrFeNiTi0.5W0.5 High Entropy Alloy Coatings Manufactured by Laser Cladding

2019 ◽  
Vol 956 ◽  
pp. 154-159 ◽  
Author(s):  
Hui Liang ◽  
Bing Yang Gao ◽  
Ya Ning Li ◽  
Qiu Xin Nie ◽  
Zhi Qiang Cao
Keyword(s):  
Wear Resistance ◽  
Laser Cladding ◽  
Dendritic Structure ◽  
Laves Phase ◽  
High Entropy Alloy ◽  
Second Phase ◽  
Laves Phases ◽  
High Entropy ◽  
Two Phases ◽  
Bcc Phase

For the purpose of expanding the application scope of HEA coating manufactured on the surface modification of materials, in this work, the Al1.5CrFeNiTi0.5 and Al1.5CrFeNiTi0.5W0.5 HEA coatings were successfully manufactured using laser cladding method on SUS304. The microstructures and wear resistance of coatings are researched systematically. It is found that the W0 and W0.5 HEA coatings all exhibit the dendritic structure, which are constituted by BCC phases and Laves phases. With W element addition, the phase structures of W0.5 coating remain unchanged. W is dissolved in both two phases, but the solid solubility in Laves phase is higher compared to that in BCC phase. W0.5 coating with the highest microhardness of 848.34 HV, and the W0 coating with the microhardness of 811.45 HV, both of whose microhardness are four times more than that of SUS304 substrate. Among all samples, the W0.5 coating shows the optimal wear performance because of its larger content of hard second phase ( Laves phase).

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