Theory of screw dislocation strengthening in random BCC alloys from dilute to “High-Entropy” alloys

Maresca, Francesco; Curtin, W.A.

doi:10.1016/j.actamat.2019.10.007

Cited by 180 publications

(105 citation statements)

References 54 publications

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“…The dislocation cell size can be expressed as

where ν is Poisson’s ratio, T is the deformation temperature, N is the dislocation impingement factor taken as 1 for this calculation, μ is the shear modulus, b is the magnitude of the Burgers vector, and ρ is the dislocation density. The dislocation statistical entropy is expressed as

where k B is the Boltzmann constant,

is the limiting value for the strain rate if the material were deformed at the speed of sound,

is the deformation strain rate, and υ is the vacancy migration frequency ( 34 – 36 ). υ showed no substantial influence on the cell size, indicating that the vacancy stabilization effect due to hydrogen bears little influence on the cell structure.…”

Section: Discussionmentioning

confidence: 99%

Hydrogen embrittlement through the formation of low-energy dislocation nanostructures in nanoprecipitation-strengthened steels

Gong

Nutter

Rivera-Dı́az-del-Castillo

et al. 2020

Sci. Adv.

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Hydrogen embrittlement is shown to proceed through a previously unidentified mechanism. Upon ingress to the microstructure, hydrogen promotes the formation of low-energy dislocation nanostructures. These are characterized by cell patterns whose misorientation increases with strain, which concomitantly attracts further hydrogen up to a critical amount inducing failure. The appearance of the failure zone resembles the “fish eye” associated to inclusions as stress concentrators, a commonly accepted cause for failure. It is shown that the actual crack initiation is the dislocation nanostructure and its associated strain partitioning.

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“…The dislocation cell size can be expressed as

where k B is the Boltzmann constant,

is the limiting value for the strain rate if the material were deformed at the speed of sound,

Section: Discussionmentioning

confidence: 99%

Hydrogen embrittlement through the formation of low-energy dislocation nanostructures in nanoprecipitation-strengthened steels

Gong

Nutter

Rivera-Dı́az-del-Castillo

et al. 2020

Sci. Adv.

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“…1. Our message is that, compared with simple metals and traditional solutions 94 , the concentrated HEAs are more conducive to heterogeneous microstructure and hence tend to be plastically nonhomogeneous 95 . Pronounced strengthening naturally follows from these roadblocks to dislocations, elevating the back stresses to unusually high levels (see Fig.…”

mentioning

confidence: 89%

Tailoring heterogeneities in high-entropy alloys to promote strength–ductility synergy

2019

Nat Commun

347

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Conventional alloys are usually based on a single host metal. Recent high-entropy alloys (HEAs), in contrast, employ multiple principal elements. The strength of HEAs is considerably higher than traditional solid solutions, as the many constituents lead to a rugged energy landscape that increases the resistance to dislocation motion, which can also be retarded by other heterogeneities. The wide variety of nanostructured heterogeneities in HEAs, including those generated on the fly during tensile straining, also offer elevated strain-hardening capability that promotes uniform tensile ductility. Citing recent examples, this review explores the multiple levels of heterogeneities in multi-principal-element alloys that contribute to lattice friction and back stress hardening, as a general strategy towards strength–ductility synergy beyond current benchmark ranges.

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“…This is understandable, because the heterogeneity in local composition and arrangements of the multiple elements makes each local region different, with or without the presence of the dislocation. The screw dislocation can adopt a kinked configuration that lowers the overall energy upon a favorable composition fluctuation (15). However, the easier kink nucleation in an HEA does not mean that screw dislocations would now be highly mobile.…”

Section: Significancementioning

confidence: 99%

Unusual activated processes controlling dislocation motion in body-centered-cubic high-entropy alloys

Chen

Zong

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

144

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Atomistic simulations of dislocation mobility reveal that body-centered cubic (BCC) high-entropy alloys (HEAs) are distinctly different from traditional BCC metals. HEAs are concentrated solutions in which composition fluctuation is almost inevitable. The resultant inhomogeneities, while locally promoting kink nucleation on screw dislocations, trap them against propagation with an appreciable energy barrier, replacing kink nucleation as the rate-limiting mechanism. Edge dislocations encounter a similar activated process of nanoscale segment detrapping, with comparable activation barrier. As a result, the mobility of edge dislocations, and hence their contribution to strength, becomes comparable to screw dislocations.

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Theory of screw dislocation strengthening in random BCC alloys from dilute to “High-Entropy” alloys

Cited by 180 publications

References 54 publications

Hydrogen embrittlement through the formation of low-energy dislocation nanostructures in nanoprecipitation-strengthened steels

Hydrogen embrittlement through the formation of low-energy dislocation nanostructures in nanoprecipitation-strengthened steels

Tailoring heterogeneities in high-entropy alloys to promote strength–ductility synergy

Unusual activated processes controlling dislocation motion in body-centered-cubic high-entropy alloys

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