Lattice Distortions in the FeCoNiCrMn High Entropy Alloy Studied by Theory and Experiment

Oh, Hyun Seok; Ma, Duancheng; Leyson, Gerard; Grabowski, Blazej; Park, Eun Soo; Körmann, Fritz; Raabe, Dierk

doi:10.3390/e18090321

Cited by 178 publications

(87 citation statements)

References 45 publications

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“…31,32 Solid solution hardening-effect of individual elements The CoCrFeMnNi HEA is a highly alloyed material, and a severe lattice distortion and high solid solution hardening effect have been expected. 14,33 However, the effect of individual elements on the strength, which is highly necessary for an alloy design of HEAs with an improved strength, is insufficiently known. One study presented a systematic report for the effect of individual elements on the strength of this alloy: the yield strength (YS) of the CoCrFeNi, CoCrMnNi, CoFeMnNi HEA as well as the CoCrFeMnNi HEA.…”

Section: Resultsmentioning

confidence: 99%

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

et al. 2018

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Although high-entropy alloys (HEAs) are attracting interest, the physical metallurgical mechanisms related to their properties have mostly not been clarified, and this limits wider industrial applications, in addition to the high alloy costs. We clarify the physical metallurgical reasons for the materials phenomena (sluggish diffusion and micro-twining at cryogenic temperatures) and investigate the effect of individual elements on solid solution hardening for the equiatomic CoCrFeMnNi HEA based on atomistic simulations (Monte Carlo, molecular dynamics and molecular statics). A significant number of stable vacant lattice sites with high migration energy barriers exists and is thought to cause the sluggish diffusion. We predict that the hexagonal close-packed (hcp) structure is more stable than the face-centered cubic (fcc) structure at 0 K, which we propose as the fundamental reason for the micro-twinning at cryogenic temperatures. The alloying effect on the critical resolved shear stress (CRSS) is well predicted by the atomistic simulation, used for a design of non-equiatomic fcc HEAs with improved strength, and is experimentally verified. This study demonstrates the applicability of the proposed atomistic approach combined with a thermodynamic calculation technique to a computational design of advanced HEAs.

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Section: Resultsmentioning

confidence: 99%

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

et al. 2018

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“…Similarly, recent studies, both theoretical and experimental ones, do not support the original idea of 'severe' lattice distortions [16,17,18]. Combined theoretical and experimental study [16] revealed that the mean strains in CoCrFeMnNi are relatively small, below 1%, but their fluctuations are significant. The hypothesis about the 'cocktail' effect is probably most vaguely defined and difficult to test it rigorously [13].…”

Section: Introductionmentioning

confidence: 80%

“…Tsai et al [19] estimated two different values of the interdiffusion coefficients, as shown in Figure 3b. In response [54] to the comment [53], they defended their approach of estimating two different interdiffusion To instigate further on this issue, two sentences from the manuscript by Tsai et al [16] are highlighted:…”

Section: 4mentioning

confidence: 99%

A Mystery of "Sluggish Diffusion" in High-Entropy Alloys: The Truth or a Myth?

et al. 2018

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High entropy alloys (HEAs) are considered as a novel class of materials with a large number of components (five and more) available in equiatomic or nearly equatomic proportions.One of the characteristic properties of HEAs was believed to be so-called 'sluggish' diffusion that should be crucial for intended high-temperature technological applications. The faith on this myth instead of rigorous experimental analysis played such a dominant role that the first set of data on interdiffusion, in fact based on an improper analysis, were cited in hundreds of articles to state the presence of sluggishness of diffusion rates in high entropy alloys.In this review, the recent data on atomic diffusion in HEAs are presented and critically discussed. The discussion is focused on tracer diffusion which is already measured dominantly for polycrystalline, but in some cases for single crystalline high-entropy alloys. The radiotracer technique provided a unique access to the diffusion rates of elements in the alloys and in fortunate cases these transport quantities could be measured in a single experiment, as in the case of Co, Cr, Fe and Mn diffusion in the CoCrFeMnNi HEA.Alternatively, a rigorous analysis of the interdiffuson experiments, which provide the diffusion rates of chemical species, too, becomes more and more sophisticated for three and more elements in an alloy and it is challenging to derive physically sound quantities from a general multicomponent diffusion experiment. Most promising in this case is the diffusion couple technique, especially the so-called pseudo-binary approach. This approach is analyzed with a focus on the applicability and the possible errors induced if up-hill diffusion appears.In the overview, it is shown that atomic diffusion in HEAs cannot a priori be considered as sluggish and both atomic interactions as well as correlation effects are responsible for the observed trends. Even if estimated on the same homologous scale, the diffusion retardation induced by a 'high entropy' in FCC crystals is not simply proportional to the number of alloying components and it is shown to be similar to that induced by, e.g., the L1 2 ordering in a binary system. Furthermore, the importance of cross-correlations in diffusion of different species in HEAs is highlighted. * Since there is no consensus about the way to list the principal elements in HEAs (alphabetic order, periodic table order, atomic percentage, etc), we will use the simple alphabetic order, as e.g. CoCrFeMnNi for the Cantor system.

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“…As we are interested in the impact of internal atomic relaxations, the total energy above is split into the contributions arising from the static bcc lattice, E σ static , and the energy contribution due to internal relaxations, denoted as ∆E σ relax . Indeed, lattice distortions constitute one of the main features in HEAs [7][8][9], and have been investigated, for example, for the FeCoNiCrMn (Cantor) HEA recently [25]. For binary alloys, the importance of relaxation energies to phase stability computations have been recognized some time ago (e.g., [26][27][28]).…”

Section: Resultsmentioning

confidence: 99%

Interplay between Lattice Distortions, Vibrations and Phase Stability in NbMoTaW High Entropy Alloys

Körmann

Sluiter

2016

Entropy

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Refractory high entropy alloys (HEA), such as BCC NbMoTaW, represent a promising materials class for next-generation high-temperature applications, due to their extraordinary mechanical properties. A characteristic feature of HEAs is the formation of single-phase solid solutions.For BCC NbMoTaW, recent computational studies revealed, however, a B2(Mo,W;Nb,Ta)-ordering at ambient temperature. This ordering could impact many materials properties, such as thermodynamic, mechanical, or diffusion properties, and hence be of relevance for practical applications. In this work, we theoretically address how the B2-ordering impacts thermodynamic properties of BCC NbMoTaW and how the predicted ordering temperature itself is affected by vibrations, electronic excitations, lattice distortions, and relaxation energies.

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Lattice Distortions in the FeCoNiCrMn High Entropy Alloy Studied by Theory and Experiment

Cited by 178 publications

References 45 publications

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

A Mystery of "Sluggish Diffusion" in High-Entropy Alloys: The Truth or a Myth?

Interplay between Lattice Distortions, Vibrations and Phase Stability in NbMoTaW High Entropy Alloys

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