The formation of octonary DyErGdHoLuScTbY and senary DyGdHoLaTbY and ErGdHoLaTbY high-entropy alloys (HEAs) with the hexagonal close-packed (HCP) structure was reported in this study. Experiments using scanning electron microscopy and x-ray diffraction confirmed the single HCP solid solution in the as-cast state for these three HEAs if the presence of minor rare-earth oxides due to contamination from processing is ignored. The measured compressive yield stress values for these HEAs at room temperature are 245, 205, and 360 MPa for the ErGdHoLaTbY, DyGdHoLaTbY, and DyErGdHoLuScTbY HEAs, respectively. The corresponding solid solution strengthening contributions for these HEAs were estimated using a simple elastic model, and the resulting contributions were 28 MPa, 27 MPa, and 42 MPa for the three aforementioned HEAs.The formation of octonary DyErGdHoLuScTbY and senary DyGdHoLaTbY and ErGdHoLaTbY high-entropy alloys (HEAs) with the hexagonal close-packed (HCP) structure was reported in this study. Experiments using scanning electron microscopy and x-ray diffraction confirmed the single HCP solid solution in the as-cast state for these three HEAs if the presence of minor rare-earth oxides due to contamination from processing is ignored. The measured compressive yield stress values for these HEAs at room temperature are 245, 205, and 360 MPa for the ErGdHoLaTbY, DyGdHoLaTbY, and DyErGdHoLuScTbY HEAs, respectively. The corresponding solid solution strengthening contributions for these HEAs were estimated using a simple elastic model, and the resulting contributions were 28 MPa, 27 MPa, and 42 MPa for the three aforementioned HEAs.
Last. Janez Dolinšek(University of Ljubljana)H-Index: 20
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Abstract Rare-earth (RE) based hexagonal high-entropy alloys (HEAs) containing elements from the heavy half of the RE series (from Gd to Lu) are considered as prototypes of an ideal HEA, stabilized by the entropy of mixing with completely random distribution of the elements on an almost undistorted hexagonal close-packed (hcp) lattice. Here we present a study of the Ce-Gd-Tb-Dy-Ho hexagonal HEA (abbreviated as HEA-Ce), where a light-RE element Ce is alloyed with four heavy-RE elements. Since the...
Abstract This paper reviews the three main approaches for predicting the formation of concentrated solid solution alloys (CSSA) and for modeling their thermodynamic properties, in particular, utilizing the methodologies of empirical thermo-physical parameters, CALPHAD method, and first-principles calculations combined with hybrid Monte Carlo/Molecular Dynamics (MC/MD) simulations. In order to speed up CSSA development, a variety of empirical parameters based on Hume-Rothery rules have been devel...
#1Ruzica Djenadic(KIT: Karlsruhe Institute of Technology)H-Index: 10
#2Abhishek Sarkar(Indian Institute of Technology Madras)H-Index: 12
Last. Horst Hahn(KIT: Karlsruhe Institute of Technology)H-Index: 81
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Multicomponent rare earth oxide (REO) nanocrystalline powders containing up to seven equiatomic rare earth elements were successfully synthesized in a single-phase CaF2-type (Fm-3 m) structure. The addition of more than six elements resulted in the formation of a secondary phase. Annealing at 1000°C for 1 h led to the formation of a single-phase (Ia-3) even in the 7-component system. In the absence of cerium (Ce4+), secondary phases were observed irrespective of the number of cations or the exte...
#1Yuan Yuan(USTB: University of Science and Technology Beijing)H-Index: 5
#2Yuan Wu(USTB: University of Science and Technology Beijing)H-Index: 37
Last. Zhaoping Lu(USTB: University of Science and Technology Beijing)H-Index: 56
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Abstract In this paper, we report the development of rare-earth high-entropy alloys (RE-HEA) with multiple principle elements randomly distributed on a single hexagonal close-packed (HCP) lattice. Our work demonstrated that it is the entropy, rather than other atomic factors such as enthalpy, atomic size and electronegativity, that dictates phase formation in the current rare-earth alloy system. The high configuration entropy stabilized the crystalline structure from phase transformation during ...
#1Yiping Lu(DUT: Dalian University of Technology)H-Index: 30
#1Yiping Lu(DUT: Dalian University of Technology)H-Index: 5
Last. Tingju Li(DUT: Dalian University of Technology)H-Index: 26
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High entropy alloys (HEAs) usually possess weak liquidity and castability, and considerable compositional inhomogeneity, mainly because they contain multiple elements with high concentrations. As a result, large-scale production of HEAs by casting is limited. To address the issue, the concept of eutectic high entropy alloys (EHEAs) was proposed, which has led to some promise in achieving good quality industrial scale HEAs ingots, and more importantly also good mechanical properties. In the pract...
Last. Shengmin Guo(LSU: Louisiana State University)H-Index: 23
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Discovery of new single-phase high-entropy alloys (HEAs) is important to understand HEA formation mechanisms. The present study reports computational design and experimental validation of a senary HEA, HfNbTaTiVZr, in a body-centered cubic structure. The phase diagrams and thermodynamic properties of this senary system were modeled using the CALPHAD method. Its atomic structure and diffusion constants were studied using ab initio molecular dynamics simulations. The microstructure of the as-cast ...
#1Y.F. Ye(CityU: City University of Hong Kong)H-Index: 13
#2Q. Wang(CityU: City University of Hong Kong)H-Index: 13
Last. Yong Yang(CityU: City University of Hong Kong)H-Index: 45
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High-entropy alloys (HEAs) are presently of great research interest in materials science and engineering. Unlike conventional alloys, which contain one and rarely two base elements, HEAs comprise multiple principal elements, with the possible number of HEA compositions extending considerably more than conventional alloys. With the advent of HEAs, fundamental issues that challenge the proposed theories, models, and methods for conventional alloys also emerge. Here, we provide a critical review of...
The microstructures and properties of high-entropy alloys (HEAs) based on the face-centered cubic and body-centered cubic structures have been studied extensively in the literature, but reports on HEAs in the hexagonal close-packed (HCP) structure are very limited. Using an efficient strategy in combining phase diagram inspection, CALPHAD modeling, and ab initio molecular dynamics simulations, a variety of new compositions are suggested that may hold great potentials in forming single-phase HCP ...
#1Y.J. Zhao(TUT: Taiyuan University of Technology)H-Index: 1
#1Ya Zhao(TUT: Taiyuan University of Technology)H-Index: 6
Last. Yang Zhang(USTB: University of Science and Technology Beijing)H-Index: 16
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Abstract The formation of disordered solid solution in the hexagonal close-packed (hcp) structure in the GdHoLaTbY alloy and its mechanical properties were investigated in this study. The single hcp phase of the alloy in the as-cast state was confirmed by X-ray diffraction and scanning electron microscopy analyses. The compressive yield strength, fracture strength, and plastic strain of the alloy are 108 MPa, 880 MPa, and 21.8%, respectively, and the Vickers hardness is 96 HV. The results show t...
Abstract A senary ScYLaTiZrHf alloy was investigated for its ability to form a solid solution with an hcp structure, also known as a high-entropy alloy (HEA). X-ray diffraction analysis of the ScYLaTiZrHf alloy produced by arc-melting method confirmed this hcp structure. The microstructure of the ScYLaTiZrHf was composed of dual phases that were enriched in (Y, La) or (Ti, Zr, Hf), with Sc distributed evenly across both phases. The positive mixing enthalpy of 11.4 kJ mol −1 derived from Miedema'...
Abstract null null High-entropy alloys (HEAs) are a new class of alloys that consist of at least five major elements in equimolar or near-equimolar ratios with atomic concentration between 5% and 35%. Many HEAs containing the ferromagnetic elements Fe, Co and Ni show soft magnetic properties, while few HEAs present hard magnetic properties. In this paper, we design and prepare the Nd20Pr20La20Fe20Co10Al10 HEA with hard magnetic property. The magnetic property and microstructure of this alloy hav...
Abstract In this work, the relationship between configuration entropy and isothermal magnetic entropy change (ΔSM) of rare earth high-entropy alloys (HEAs) was studied. The results show that the matrix of rare earth HEAs GdTbHoEr exhibits the largest refrigerant capacity up to now (about 924.48 J kg−1 at a 5 T magnetic field). With the addition of non-magnetic elements La and Y, the configuration entropy increases, but the values of ΔSM and the refrigerant capacity decrease from 8.64 to 5.85 J k...
#1Yongyun Zhang(Southern University of Science and Technology)H-Index: 2
#2Tieyuan Bian(Southern University of Science and Technology)
Last. Peng Yu(Southern University of Science and Technology)H-Index: 16
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Abstract CoCrFeNiMn high entropy alloy samples produced by metal injection molding were sintered in different temperatures to investigate the sintering mechanism. The sintered CoCrFeNiMn samples have a matrix with FCC structure. However, a precipitate phase, which is Cr-rich and has a BCC structure different from the σ phase discovered in previous researches, is observed in all the samples sintered at different temperatures. The precipitates are distributed in the grain boundaries. Its morpholog...
Abstract According to a recent Hume-Rothery approach, the electron concentration, e/a, and the average radius can be used to identify the domain of stability of HEAs and to estimate the phases that may occur in the alloy. The present study investigates the influence of the electronic structure and the average radius on the hardness for a series of HEA alloys. The alloys investigated in this work all contained Co, Fe and Ni as base elements. To this base system one or more elements were added, in...
#2Nan-nan Zhang(SUT: Shenyang University of Technology)H-Index: 1
Last. De-yuan Li(SUT: Shenyang University of Technology)H-Index: 1
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Al0.5Cr0.9FeNi2.5Vx (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) multi-principal alloys were prepared by vacuum arc melting. The effect of vanadium addition on its microstructure and properties was investigated. The results show that the alloys of all components exhibited an FCC single-phase structure. With the addition of vanadium, the microstructure of the alloy changed from dendrites to equiaxed crystals, the grains were remarkably refined, and the layered CrV phase was exhibited, which improved the prop...
Last. Junwei Qiao(TUT: Taiyuan University of Technology)H-Index: 29
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Single-phase hexagonal close-packed structure of the ScYLaGdTbDyHoErLu high-entropy alloy was studied in detail. The applicability of the rule of mixture was analyzed with respect to the lattice constant, mechanical parameters, elastic properties, melting point, and hardness of the alloy. Significant tension-compression asymmetry has been found and explained by the strength differential effect during the uniaxial tests. Numerous deformation twins and high densities of stacking faults can be obse...
Transformation induced plasticity (TRIP) effect in high entropy alloys (HEAs) overcomes the strength–ductility “trade-off” and leads to the synchronous improvement of strength and ductility. In this work, we studied a TRIP Fe60Mn20Co10Cr10 HEA with a dual-phase structure consisting of face-centered cubic matrix and hexagonal close-packed (HCP) martensite. By warm-rolling and subsequent annealing, three samples with different recrystallization conditions and HCP phase volume fractions were obtain...
Abstract A low density refractory high entropy alloy of composition TiCrVNb0.5Al0.5 was prepared by vacuum arc melting. Due to the formation of a single-phase BCC structure with uniform element distribution and a gradient passive film with a high concentration of passivating elements, the TiCrVNb0.5Al0.5 high entropy alloy (HEA) exhibits low corrosion current density (10−7~10−8 A cm−2), high breakdown potential (1.8–1.9 VSCE) and excellent repassivation ability in 3.5 wt% NaCl and 1M HCl solutio...