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High Entropy Alloys（2022）
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Research Progress in Refractory High Entropy Alloys for Nuclear Applications
ZHANG Ping, JIANG Li, YANG Jinxue, SU Zhengxiong, WANG Jianqiang, SHI Tan, LU Chenyang
Materials Reports
2022,36(14 ):22060260 -22. DOI:10.11896/cldb.22060260
Abstract
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Search of nuclear structural materials with excellent comprehensive properties is one of the significant challenges in advanced reactor development. Refractory high entropy alloys (RHEAs), which have body-centered cubic structures and contain multiple refractory elements as major alloying elements, have great advantages on irradiation tolerance and high-temperature strength, and thus are promising candidates for nuc-lear structural materials. In this review, the research progress of RHEAs for nuclear applications is summarized from aspects of alloy design and fabrication, phase structure and phase stability, mechanical property, corrosion resistance, as well as radiation resistance. The future research directions and potential nuclear application scenarios of RHEAs are also presented.
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Microstructure and Mechanical Properties of In-situ Carbides Reinforced CoCrFeNi High-entropy Alloys
CHEN Ruirun, CHEN Xiugang, GAO Xuefeng, QIN Gang, SONG Qiang, CUI Hongzhi
Materials Reports
2022,36(14 ):22050073 -6. DOI:10.11896/cldb.22050073
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In order to strengthen FCC-type high-entropy alloy (HEA), Ti and C were added to FCC single-phase CoCrFeNi HEA to realize the strengthening effect. (CoCrFeNi)
100-
x
(TiC)
x
(
x
=0, 2, 4, 6, 8(atomic fraction,%)) was prepared by vacuum arc melting. Effects of different contents of Ti and C on the microstructure and mechanical properties of CoCrFeNi HEA were studied. The results show that after adding Ti and C, the microstructure of (CoCrFeNi)
100-
x
(TiC)
x
changes from single FCC phase to FCC matrix phase and in-situ Ti-rich carbides. The formation of Ti-rich carbides does not change the type of matrix phase. Ti-rich carbides solidify along the interdendrite, which is lamellar and connected with each other to form a network structure. With the increase of Ti and C content, the content of FCC matrix phase gradually decreases, and the vo-lume fraction of Ti-rich carbides gradually increases to 12%. The tensile test results show that with the increase of Ti-rich carbides content, the yield strength and tensile strength of the alloy increase continuously, while the elongation decreases; with
x
=8, the tensile strength can be increased from 409 MPa (
x
=0) to 618 MPa, with the applicable plasticity maintained, and the elongation can still reach 15.7%. The hardness test results show that the hardness of the alloy increases with the increase of Ti rich carbides content; with
x
=8, the hardness value is 253HV
0 2
. The second phase strengthening of in-situ Ti-rich carbides, solid solution strengthening and the synergistic effect of dendritic lamellar and network structure improve the strength of the alloy and ensures its good plasticity.
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Preparation and Electrocatalytic Oxygen Evolution Performances of High-entropy Alloy FeCoNiCrP
PAN Ye, ZHONG Xu, ZHU Yin'an, LU Tao, YU Jin
Materials Reports
2022,36(14 ):22020109 -5. DOI:10.11896/cldb.22020109
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In this work, high-entropy alloy FeCoNiCrP nanoparticles were prepared by mechanical alloying method, and loaded onto carbon fiber paper as working electrode. The electrocatalysis oxygen evolution performance of the alloy was tested. Cyclic voltammetry was utilized to electrochemically activate the catalyst. After cyclic voltammetry activation, the FeCoNiCrP catalyst only requires an overpotential of 286 mV to drive a current density of 10 mA/cm
2
in 1 mol/L KOH medium, better than its pristine catalyst. The activated catalyst also has a lower Tafel slope (27.6 mV/dec), a larger double-layer capacitance (0.435 mF) and the more excellent stability under 20 h testing at fixed potential. Cyclic voltammetry activation has an influence on surface morphology, which constructs a core-shell structure and forms metal oxides and hydroxyl oxides that are conducive to the oxygen evolution process, and ultimately enhances the oxygen evolution performance of the catalyst.
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Preparation, Microstructure Evolution and Mechanical Properties of AlCoCrFeNi High-entropy Alloys with Harmonic Heterostructure
XIU Mingqing, LI Tianxin, ZHANG Guojia, ZOU Longjiang, LU Yiping
Materials Reports
2022,36(14 ):22030309 -5. DOI:10.11896/cldb.22030309
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Akind of AlCoCrFeNi high-entropy alloy (HEA) with harmonic heterostructure composed of outer fine grains and inner coarse grains was prepared by mechanical ball milling and spark plasma sintering. The quasi-static compressive mechanical properties of the alloy were tes-ted, and the phase structure and microstructure of the alloy were characterized. The results show that the yield strength of sintered AlCoCrFeNi HEA after ball milling is 1 686 MPa and the compressive strain rate is 16.5%. The yield strength and the compressive strain rate of the sintered AlCoCrFeNi HEA without ball milling are only 1 371 MPa and 16.2%, respectively. The yield strength and the compressive strain rate of the as-cast AlCoCrFeNi HEA are 1 363 MPa and 18.7%, respectively. Compared with the other two methods, the AlCoCrFeNi HEA prepared by ball milling and sintering has the best comprehensive mechanical property. The phase composition of the AlCoCrFeNi HEA prepared by sintering is consistent with that of the original powder, both composed of BCC+B2+FCC phase. The outer grains of the AlCoCrFeNi HEA powder were refined by mechanical ball milling, and formed harmonic heterostructure with the inner large grains. This special structure plays a role of back stress strengthening, and significantly improves the yield strength of the AlCoCrFeNi HEA.
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Study on Microstructure and Corrosion Resistance of AlMgLi
0.5
Zn
0.5
Cu
0.2
Light-weight High-entropy Alloy
HU Yong, LIU Fei, LIU Yuanyuan, ZHAO Longzhi, JIAO Haitao, TANG Yanchuan, LIU Dejia
Materials Reports
2022,36(14 ):22010093 -6. DOI:10.11896/cldb.22010093
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AlMgLi
0.5
Zn
0.5
Cu
0.2
light-weight high-entropy alloy was fabricated by magnetic levitation melting with five light weight elements Al, Mg, Li, Cu and Zn. The effect of heat treatment on the microstructure of the AlMgLi
0.5
Zn
0.5
Cu
0.2
light-weight high-entropy alloy was analyzed by XRD and SEM. The density and corrosion resistance of the AlMgLi
0.5
Zn
0.5
Cu
0.2
light-weight high-entropy alloy were tested by ES-D electronic balance and CS350 electrochemical workstation, respectively. The results show that the density of the AlMgLi
0.5
Zn
0.5
Cu
0.2
light-weight high-entropy alloy is 2.851 g/cm
3
. The eutectic microstructure containing Mg
32
(AlZn)
49
phase at the grain boundary of the AlMgLi
0.5
Zn
0.5
Cu
0.2
light-weight high-entropy alloy decreases and its morphology changes from strip to point after heat treatment. The dendrite microstructure of FCC1 phase becomes finer and more uniform. After the heat treatment at 300 ℃, the Cu element on the surface of FCC1 phase is solidly dissolved into the matrix, improving the corrosion resistance of the alloy. However, after the heat treatment at 300 ℃+120 ℃, FCC1 becomes equiaxed and FCC2 (Cu-rich phase) precipitates on the substrate surface of FCC1, forming a micro-corrosion battery, which reduces the corrosion resistance of the alloy.
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Effect of Annealing on Microstructure and Corrosion Resistance of the Co
x
CrFeMnNi
2-
x
High-entropy Alloys
WANG Quan, WU Changjun, XU Xuewei, PENG Haoping, LIU Ya, SU Xuping
Materials Reports
2022,36(11 ):21110150 -7. DOI:10.11896/cldb.21110150
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Aseries of fcc-type Co
x
CrFeMnNi
2-
x
(
x
=0.25—1.5) high-entropy alloys were prepared by arc melting method and were vacuum annealed at 600—1 000 ℃ for 120—360 h in this work. The influence of Co and Ni contents, annealing temperature and annealing time on microstructure and corrosion resistance of these alloys were investigated. The results show that all the investigated as-cast alloys are composed of single fcc phase. Except for Co
1.5
CrFeMnNi
0.5
alloy, in which a small amount of hcp phase is formed, there is no phase transformation or precipitation in other alloys after 600—1 000 ℃ annealing. The as-cast Co
x
CrFeMnNi
2-
x
alloys are mainly composed of coarse dendrites. Their corrosion resis-tance gradually decreases with the increase of Co content. Experimental results indicate that the metallographic microstructure of the Co
x
CrFeMnNi
2-
x
alloys significantly change after annealing. The dendritic structure of these alloys becomes much finer after 600 ℃ annealing, because the trunks of the dendrites are truncated by grain boundary migration. The corrosion resistance of the alloys are significantly reduced due to the increase of coarse grain boundary. After annealing at 800 ℃ for 120 h, tortuous equiaxed grain boundaries are formed with corrosion resistance greatly improved, while the woven net-like subcrystals still exist in the equiaxed grains. Moreover, further prolonging annealing time or increasing annealing temperature can smoothen and refine the grain boundaries. The woven network sub-crystals in the crystal gradually disappear, and the corrosion resistance of the alloys is further improved. These results will provide a basis for designing and microstructure controlling of the fcc-type high-entropy alloys.
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Microstructure and Mechanical Properties of Non-equiato Al
x
(FeCoNiCr)
88-
x
Mn
12
High-entropy Alloys
ZHAO Kun, BO Haiwa, AI Taotao, LIAO Zhongni, DING Liu, FENG Xiaoming
Materials Reports
2022,36(14 ):22040007 -7. DOI:10.11896/cldb.22040007
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Al
x
(FeCoNiCr)
88-
x
Mn
12
(
x
=0,4,12,24) high-entropy alloys were prepared by dry ball milling, vacuum hot-pressing sintering and annealing process. The effect of different Al content and annealing temperature on the microstructure and mechanical properties of the alloys was stu-died. The results show that Al
x
(FeCoNiCr)
88-
x
Mn
12
HEAs were composed of FCC+BCC dual phases, and the BCC phases increased with the increase of Al content. The Al
4
(FeCoNiCr)
84
Mn
12
alloy had higher comprehensive mechanical properties, the compressive yield strength was 572.7 MPa, the ultimate compressive strength was 1 759.3 MPa and the fracture strain was 39.9%. The mechanical properties of the alloy were further improved and the texture in BCC phases was more pronounced after annealing at 650 ℃ for 1 h. The excellent mechanical properties of the Al
4
(FeCoNiCr)
84
Mn
12
alloy are attributed to the second-phase strengthening and Hall-Petch effect, and the adjustment effect of small angle grain boundaries of BCC phases.
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Effect of Nano WC on Wear and Corrosion Resistances of AlCoCrFeNi High-entropy Alloy Coating
CHONG Zhenzeng, SUN Yaoning, CHENG Wangjun, HAN Chenyang, SU Caijin, NAFITHA Delichti, FAN Zilong
Materials Reports
2022,36(14 ):22030230 -6. DOI:10.11896/cldb.22030230
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AlCoCrFeNi high-entropy alloys have good mechanical properties, wear resistance, and corrosion resistance, which can be used as a coating material for vulnerable parts. AlCoCrFeNi and AlCoCrFeNi+WC(5wt%) high-entropy alloy powders were pretreated by mechanical powder mixing, and afterwards the coatings were prepared by laser melting on the surface of 45# steel, in order to further improve its performance. The surface morphology, microstructure, element distribution, microhardness, friction wear, and corrosion resistance of the two coatings were comparatively studied. The results show that the surface roughness of the AlCoCrFeNi+WC(5%) coating is lower, that the coating still has a body-centered cubic structure (BCC/B2) and that the grain structure of the coating has been refined, with W and Cr elements concentrated at the grain boundaries. The average microhardness of the coating was increased from 500HV to 600HV due to the combined effect of fine grain strengthening and second phase strengthening. The Si
3
N
4
sphere with 4 mm diameter was selected as the friction substrate and tested under a load of 10 N for 30 min. The doping of WC reduced the friction coefficient from 0.8 to 0.6, the wear weight loss was reduced by 0.84 mg, the width and depth of wear scratches were minimized, and the wear level was lighter, compared with those of the AlCoCrFeNi coating. In the electrochemical test with a 3.5wt% NaCl solution, the self-corrosion potential of the WC-doped coating increased by 0.042 V, while the self-corrosion current density reduced by one order of magnitude, and the WC-doped coating exhibited a larger capacitive arc diameter. After the test, the AlCoCrFeNi+WC(5%) coating showed lighter corrosion, and the corrosion pits on its surface were significantly reduced. These results indicate that the addition of nano WC can effectively improve the wear and corrosion resistances of the AlCoCrFeNi high-entropy alloy coating.
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First Principles Calculation of Structural Stability and Mechanical Properties of FeAlNiCrMn High Entropy Alloy
CHANG Chao, ZHANG Hui, LAI Yuan, LI Liang, BAI Xiaoxu
Materials Reports
2022,36(14 ):21040230 -5. DOI:10.11896/cldb.21040230
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The effects of pressure on the structure, elastic constants, ductile-brittleness and elastic anisotropy of FeAlNiCrMn high entropy alloy were studied by first principles. The influence of pressure on the structural stability of the alloy was investigated by calculating the lattice constant, binding energy and density of states of the alloy with the pressure-inducing. The toughness and brittleness of the alloy in the pressure range of 0—100 GPa were studied by
B
/
G
ratio, Poisson's ratio
ν
and Cauchy pressure. As the pressure increases, the modulus, melting point and hardness of the alloy will increase gradually. Finally, the transition process of the alloy from anisotropy to isotropy with the increase of pressure had been analyzed in detailed.
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Effect of Ferro-Boron Powder Addition on the Tissue Morphology and Properties of AlCoCrFeNi High-entropy Alloy by Laser Cladding
GU Mi, SUN Ronglu, NIU Wei, HAO Wenjun, ZUO Runyan
Materials Reports
2022,36(8 ):20120230 -5. DOI:10.11896/cldb.20120230
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The effect of the content of ferro-boron powder on the microstructure and properties of the laser cladding AlCoCrFeNi high-entropy alloy coa-ting on the surface of 45 steel was studied in this work. AlCoCrFeNi high-entropy alloy coatings with different contents of ferro-boron powder were prepared on the surface of 45 steel substrate by laser cladding. The surface morphology, microstructure and cross-sectional morphology of the coating were compared and analyzed, and the hardness and wear resistance were measured. The results show that the addition of ferro-boron powder to the high-entropy alloy powder can significantly improve the surface quality and refine the grains in the coating. When the mass fraction of ferro-boron powder was 3%—4%, the cladding coating surface morphology was gradually improved. When the mass fraction of ferro-boron powder was 5%—6%, a small number of nodules and cracks appeared in the coating. The hardness and the wear resistance of the high-entropy alloy coating with ferro-boron powder were improved. When the addition of ferro-boron powder was 4%, AlCoCrFeNi high-entropy alloy coating with high quality was obtained which showedexcellent comprehensive performance, microhardness and wear resistance, with no obvious nodules and cracks.
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High Entropy Alloys（2022）
