Analysis of diffusion in high entropy alloys

Paul, Tumpa R.; Belova, Irina V.; Murch, Graeme E.

doi:10.1016/j.matchemphys.2017.06.039

Cited by 39 publications

(25 citation statements)

References 45 publications

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“…The derived values were proposed to be approximately equal to the intrinsic and tracer diffusivities of the equiatomic CoCrFeMnNi alloy with a thermodynamic factor of about unity [20]. In fact, this assumption was found to be correct in the framework of the random alloy model [27]. The observed low diffusion rates were attributed to a higher normalized activation enthalpy Q/T m (Q is the activation enthalpy and T m the melting temperature, respectively) of diffusion in HEAs in comparison to pure metals or corresponding binary and ternary alloys.…”

Section: Introductionmentioning

confidence: 89%

Tracer diffusion in single crystalline CoCrFeNi and CoCrFeMnNi high entropy alloys

et al. 2018

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Section: Introductionmentioning

confidence: 89%

Tracer diffusion in single crystalline CoCrFeNi and CoCrFeMnNi high entropy alloys

et al. 2018

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“…Another two studies [49,50], authored by the team of Murch and Belova, were widely considered to be authorities in the field of theory of diffusion. Both studies focused strictly on the theoretical description of the diffusion in high entropy alloys, with no additional experimental data.…”

Section: State-of-the-art In Theoretical Studiesmentioning

confidence: 99%

“…Studies by Allnatt et al [49] and Paul et al [50] provided a very valuable insight into the nature of correlation effects in high entropy alloys, as well as valuable theoretical tools for analysis of diffusion phenomena in high entropy alloys. However, it should be remembered that MAA-light theory, while simplified in comparison to legacy MAA, is still an extremely complex description of the diffusion process, far more complicated than the Darken or Manning theories.…”

Section: Elementmentioning

confidence: 99%

“…However, it should be remembered that MAA-light theory, while simplified in comparison to legacy MAA, is still an extremely complex description of the diffusion process, far more complicated than the Darken or Manning theories. Additionally, the conclusions formulated by Paul et al [50] should be treated very carefully, as all theoretical analyses performed in this study are based on the results by Tsai et al [28], which can be considered as controversial [46], as discussed previously. Furthermore, the use of MAA-light formalism allowed calculating the contribution of the correlation factors to total activation energies, with the highest one being determined for Mn (+12.3 kJ•mol −1 ).…”

Section: Elementmentioning

confidence: 99%

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State-of-the-Art Diffusion Studies in the High Entropy Alloys

Dąbrowa

Danielewski

2020

Metals

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The development of the high entropy alloys (HEAs) is amongst the most important topics in the field of materials science during the last two decades. The concept of multicomponent, near-equimolar systems has been already applied to the number of other systems, including oxides, carbides, diborides, silicides, and it can be expected that other groups of materials will follow. One of the main driving forces for the development of HEAs is the so-called “four core effects”: high entropy effects, severe lattice distortion, cocktail effect, and sluggish diffusion effect. Their existence and extent has been a subject of heated discussion. Probably the least studied of them is the sluggish diffusion effect, which is of the, especially, high importance from the point of view of the most possible applications of HEAs—as high-temperature materials. Its alleged existence carries a promise of obtaining materials with superior mechanical properties, higher creep resistance, and less susceptibility to high-temperature corrosion. In the current review, the state-of-the-art of diffusion studies in HEAs was presented, as well as the resulting conclusions concerning the existence of the sluggish diffusion effect. Based on the literature analysis, it can be stated that there is no experimental evidence, which would support the existence of the sluggish diffusion in HEAs on the level of tracer and self-diffusivities. Nevertheless, it can be pointed out that our current state of knowledge on the diffusion in HEAs is still far from complete; therefore, further directions of studies are proposed.

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“…In their analysis, the authors of Ref. [55] stated that the analysis of Tsai et al [19] seems to be correct in terms of the random alloy model, if relatively small corrections with respect to the correlation effects are included. We will show below that the analysis of Tsai et al [19] is basically incorrect and introduces unpredictable uncertainties in the derived values of the interdiffusion coefficients.…”

Section: Pseudo-binary And/or Quasi-binary Approachmentioning

confidence: 99%

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

Divinski

Покоев

Esakkiraja

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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Analysis of diffusion in high entropy alloys

Cited by 39 publications

References 45 publications

Tracer diffusion in single crystalline CoCrFeNi and CoCrFeMnNi high entropy alloys

Tracer diffusion in single crystalline CoCrFeNi and CoCrFeMnNi high entropy alloys

State-of-the-Art Diffusion Studies in the High Entropy Alloys

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

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