Phase selection motifs in High Entropy Alloys revealed through combinatorial methods: Large atomic size difference favors BCC over FCC

Kube, Sebastian; Sohn, So Young; Uhl, David; Datye, Amit; Mehta, Apurva; Schroers, Jan

doi:10.1016/j.actamat.2019.01.023

Cited by 195 publications

(74 citation statements)

References 58 publications

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“…Other strategies based on nanoindentation are seen in the literature to probe mechanical properties over compositional space, like the use of diffusion multiples [36,37] and of thin films prepared by combinatorial sputtering [38], which contain undoubtedly a larger number of compositions than in this work. However, the characterization of such samples is more complex and/or less precise.…”

Section: Experimental Strategies For Exploring Solid Solution Strengtmentioning

confidence: 99%

Combining experiments and modeling to explore the solid solution strengthening of high and medium entropy alloys

et al. 2019

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The mechanical properties due to solid solution strengthening are explored within the single phase fcc domain of the Co-Cr-Fe-Mn-Ni high entropy alloy (HEA) system. This is achieved by combining an efficient and reproducible metallurgical processing of alloys to X-ray diffraction and nanoindentation characterization techniques, thus enabling to get access to 24 different bulk alloys. Large variations of nanohardness are seen with composition. Experimental results are rationalized in terms of lattice misfit and elastic constant variations with alloy-composition, through the use of an analytical mechanistic theory for the temperature-, composition-and strain-rate-dependence of the initial yield strength of fcc HEAs, with predictions made using only experimental inputs. The good agreement obtained by comparing model predictions to experiments provides the basic framework for mechanical properties optimization within the Co-Cr-Fe-Mn-Ni system; the approach could be systematically applied to all classes of fcc HEAs.

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Section: Experimental Strategies For Exploring Solid Solution Strengtmentioning

confidence: 99%

Combining experiments and modeling to explore the solid solution strengthening of high and medium entropy alloys

et al. 2019

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“…The reviews published on MPEA/HEA films contain discussions of preparation methods, composition design, properties and potential applications [34,35]. In the present work, thin films were prepared by magnetron sputtering, a technique which has been successfully used for rapid atomic-scale investigations of the phase evolution of MPEA/HEA films, i.e., stability against decomposition into competing phases [36][37][38][39] and oxidation [40].…”

Section: Introductionmentioning

confidence: 99%

Microstructure evolution and thermal stability of equiatomic CoCrFeNi films on (0001) α-Al2O3

et al. 2020

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Homogeneous face-centered cubic (fcc) polycrystalline CoCrFeNi films were deposited at room temperature on (0001) a-Al 2 O 3 (c-sapphire). Phase and morphological stability of 200 to 670 nm thick films were investigated between 973 K and 1423 K. The fcc-phase persists while the original <111> texture of 30-100 nm wide columnar grains evolves into ~10 or ~1000 µm wide grains upon annealing. Only the metallic M grains having two specific orientation relationships (ORs) to the c-sapphire grow. These ORs are OR1 (M(111)[110]//a-Al 2 O 3 (0001)[1100]) and OR2 (M(111)[110]//a-Al 2 O 3 (0001)[1120]) and their twin-related variants (OR1t and OR2t). They are identical to those reported for several pure fcc metal (M) films. Thus, the ORs in these fcc/c-sapphire systems appear not to be controlled by the fcc phase chemistry or its lattice parameter as usually assumed in literature. Upon annealing, the films either retain their integrity or break-up depending on the competing kinetics of grain growth and grain boundary grooving. Triple junctions of the grain boundaries, the major actors in film stability, were tracked. Thinner films and higher temperatures favor film break-up by dewetting from the holes grooved at the triple junctions down to the substrate. Below 1000 K, the film microstructure stabilizes into 10 µm wide OR1 and OR1t twin grains independent of film thickness. Above 1000 K, the OR2 and OR2t grains expand to sizes exceeding more than a 1000 times the film thickness. The grain boundaries of the OR2 and OR2t grains migrate fast enough to overcome the nucleation of holes from which break-up could initiate. The growth of the OR2 and OR2t grains in this complex alloy is faster than in pure fcc metals at equivalent homologous annealing temperatures.

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“…In addition, the VEC was the most common phase selection criterion in the solid‐solution alloy and here we only considered the VEC of the metal elements. In this case, the VEC of (M x N 1 ‐x )B 2 solid solutions could be expressed as follows:

V E C = x V E C_{normalM} + (1 - x) V E C_{normalN},

where VEC M and VEC N were the valency of M and N metal elements, respectively, as listed in Table .…”

Section: Theoretical and Experimental Methodsmentioning

confidence: 99%

“…An effective strategy to solve this issue is the establishment of the formation criterion for solid‐solution materials. Up to now, numerous attempts have been made to establish the formation criterion for solid‐solution alloys, especially for high‐entropy alloys . Extensive experimental studies have demonstrated that the dominating factors of the formation ability for solid‐solution alloys involve atomic size difference ( δ ), mixing enthalpy, and valence electron concentration ( VEC ), which have greatly accelerated the discovery and design of solid‐solution alloys with desirable properties …”

Section: Introductionmentioning

confidence: 99%

“…WEN Et al. have been made to establish the formation criterion for solid-solution alloys, 7,8 especially for high-entropy alloys. [9][10][11] Extensive experimental studies have demonstrated that the dominating factors of the formation ability for solid-solution alloys involve atomic size difference (δ), mixing enthalpy, and valence electron concentration (VEC), which have greatly accelerated the discovery and design of solid-solution alloys with desirable properties. [7][8][9][10][11] Solid-solution ceramics with binary, [12][13][14] ternary, [15][16][17] and quaternary or more-component (also named high-entropy) structures, [18][19][20][21][22] as the new members of solid-solution materials, have been attracting a growing attention in recent years for potential applications in the structural and functional fields, especially under extreme conditions of temperature, pressure, and others.…”

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confidence: 99%

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Formation criterion for binary metal diboride solid solutions established through combinatorial methods

Wen

Liu

et al. 2020

J Am Ceram Soc

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Establishing the formation criterion is urgent for accelerating the discovery and design of solid‐solution materials with desirable properties. The previously reported formation criterion mainly focused on solid‐solution alloys, while the formation criterion was rarely established in solid‐solution ceramics. To solve this problem, herein, we take a class of solid‐solution ceramics, namely binary metal diboride ((MxN1‐x)B2) solid solutions, as a prototype. Through combinatorial methods including high‐throughput molten salt syntheses and high‐throughput first‐principles calculations combined with the machine learning approach, the correlation between influential factors, including atomic size difference (δ), mixing enthalpy at 0 K and 0 Pa (ΔHmix0K), doping condition (φ), and valence electron concentration (VEC), and the formation ability of (MxN1‐x)B2 solid solutions was first studied systematically, and then their formation criterion was well established. The results showed that the influential degree of the aforementioned four factors on the formation ability of (MxN1‐x)B2 solid solutions could be described as follows: δ > ΔHmix0K> φ > VEC. In addition, a newly proposed parameter, β, could well reflect the formation ability of (MxN1‐x)B2 solid solutions: when β > 0, the single‐phase (MxN1‐x)B2 solid solutions could be successfully synthesized in our work and vice versa. This study may provide a theoretical guidance in the discovery and design of various solid‐solution ceramics, such as the metal borides, carbides, nitrides, etc, with desirable properties.

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Phase selection motifs in High Entropy Alloys revealed through combinatorial methods: Large atomic size difference favors BCC over FCC

Cited by 195 publications

References 58 publications

Combining experiments and modeling to explore the solid solution strengthening of high and medium entropy alloys

Combining experiments and modeling to explore the solid solution strengthening of high and medium entropy alloys

Microstructure evolution and thermal stability of equiatomic CoCrFeNi films on (0001) α-Al2O3

Formation criterion for binary metal diboride solid solutions established through combinatorial methods

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