Short-range order in face-centered cubic VCoNi alloys

Kostiuchenko, Tatiana; Ruban, Andrei V.; Neugebauer, Jörg; Shapeev, Alexander V.; Körmann, Fritz

doi:10.1103/physrevmaterials.4.113802

Cited by 38 publications

(28 citation statements)

References 63 publications

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“…Cu-Pt and Pd-Au pairs (The full set of nearest neighbor order parameters are included in the Supporting Information). The degree of nearest neighbor order in AgAuCuPdPt at high temperatures is similar to other multi component alloys, such as bulk bcc NbMoTaW, 30 bulk fcc VCoNi, 31 and bulk fcc CrFeCoNi. 32 AgAuCuPdPt.…”

Section: Local Order In Bulk Agaucupdptmentioning

confidence: 55%

Local order in AgAuCuPdPt high entropy alloy surfaces

Kristoffersen

2022

Preprint

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Synthesis of high entropy alloys often involve heating precursors to above 1000°C such that entropy stabilization takes effect. The resulting alloys are characterized by random element distribution at the bulk lattice positions. Surfaces may however be more ordered, even at high temperatures. We explore the local order at (111), (100) and (533) surfaces of the equimolar fcc AgAuCuPdPt high entropy alloy at high temperatures and thermal equilibrium. We find that the local order is significantly increased at the (100) surface and to a lesser extend at the (533) and (111) surfaces compared to bulk AgAuCuPdPt. The (100) surface both segregates with increased amount of Au and Ag and less Pd and Pt and have a more ordered distribution of nearest neighbor atom pairs. The (111) surface segregates with increased amounts of Au and Ag and less Cu, Pd and Pt, but the nearest neighbor distribution is mostly random. The (100) type step edge of the (533) surface resemble the (100) surface. The degree of surface order seems linked to the structure ensemble’s energy distribution width, so we suggest that the width can be used to estimate the degree of order in high entropy alloys with minimal computational efforts.

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Section: Local Order In Bulk Agaucupdptmentioning

confidence: 55%

Local order in AgAuCuPdPt high entropy alloy surfaces

Kristoffersen

2022

Preprint

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“…The traditional solid solution strengthening models (Varvenne et al, 2017;Labusch et al, 1972) were developed with an assumption of dilute alloys, while this assumption is clearly not valid any more in the case of HEAs and MEAs, where the definitions of solute and solvent break down (Okamoto et al, 2016;Varvenne et al, 2016a;Coury et al, 2019;Zhao and Nieh, 2017). Moreover, the models for solid solution strengthening were generally based on an assumption of a random distribution of atoms in the alloy, while more recently, chemical short-range order (CSRO) (Zhang et al, 2017;Li et al, 2019;Zhang et al, 2018;Zhang et al, 2020;Fantin et al, 2020;Varvenne et al, 2016b;Sadigh et al, 2012;Kostiuchenko et al, 2020) and local composition fluctuation (Jian et al, 2020) have also been found to play important roles in the mechanical behaviors of HEAs and MEAs. The local chemical structure/ ordering and the local composition fluctuation can be experimentally characterized by extended X-ray absorption fine structure (EXAFS) techniques (Varvenne et al, 2016a;Zhang et al, 2017) and atomic resolution energy-dispersive X-ray spectroscopy (EDS) mapping using aberration-corrected TEM (Kostiuchenko et al, 2020;Zhang et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the models for solid solution strengthening were generally based on an assumption of a random distribution of atoms in the alloy, while more recently, chemical short-range order (CSRO) (Zhang et al, 2017;Li et al, 2019;Zhang et al, 2018;Zhang et al, 2020;Fantin et al, 2020;Varvenne et al, 2016b;Sadigh et al, 2012;Kostiuchenko et al, 2020) and local composition fluctuation (Jian et al, 2020) have also been found to play important roles in the mechanical behaviors of HEAs and MEAs. The local chemical structure/ ordering and the local composition fluctuation can be experimentally characterized by extended X-ray absorption fine structure (EXAFS) techniques (Varvenne et al, 2016a;Zhang et al, 2017) and atomic resolution energy-dispersive X-ray spectroscopy (EDS) mapping using aberration-corrected TEM (Kostiuchenko et al, 2020;Zhang et al, 2020). The effects of local chemical ordering and local composition fluctuation on the solid solution strengthening have also be examined by molecular dynamics (MD) simulations in a few recent studies (Sadigh et al, 2012;Rao et al, 2017a;Ding et al, 2019;Li et al, 2019;Jian et al, 2020;Chen et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Coupled Strengthening Effects by Lattice Distortion, Local Chemical Ordering, and Nanoprecipitates in Medium-Entropy Alloys

Cheng

Yuan

2021

Front. Mater.

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Extraordinary mechanical properties can be achieved in high-entropy alloys (HEAs) or medium-entropy alloys (MEAs) with nanoprecipitates. In the present study, the extra coupled strengthening effects by lattice distortion, local chemical ordering, and nanoprecipitates in the HEAs and MEAs with nanoprecipitates have been systematically investigated by large-scale molecular dynamics simulations. The moving of the dislocation can be slowed down, and the dislocation line shows a wavy configuration due to lattice distortion and local chemical ordering, resulting in strengthening. The degree of the wavy configuration increases and the sliding velocity of the dislocation decreases with increasing degrees of local chemical ordering. It is clearly indicated that the dislocation moves via nanoscale segment detrapping mechanism due to the effects of lattice distortion and local chemical ordering, resulting in roughened dislocation pathways for strengthening. The activated nanoscale segments are observed to be easier to detrap from the regions with stronger Co-Cr local chemical ordering and then propagate into the regions without such chemical ordering. These moving characteristics of the dislocation can delay the unpinning process from nanoprecipitates; thus, extra coupled strengthening effect has been revealed in the HEAs and MEAs with nanoprecipitates compared to pure Orowan’s strengthening.

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“…[3-5] A converged cluster expansion can subsequently be used in Monte Carlo simulations to compute thermodynamic properties, such as configuration entropy, [6, 7] phase diagrams, [8] ionic percolation,[9, 10] and short range order. [11,12] * †…”

mentioning

confidence: 99%

Sparse expansions of multicomponent oxide configuration energy using coherency & redundancy

Barroso-Luque,

Yang,

Ceder

2021

Preprint

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Compressed sensing has become a widely accepted paradigm to construct high dimensional cluster expansion models used for statistical mechanical studies of atomic configuration in complex multicomponent crystalline materials. However, strict sampling requirements necessary to obtain minimal coherence measurements for compressed sensing to guarantee accurate estimation of model parameters are difficult and in some cases impossible to satisfy due to the inability of physical systems to access certain configurations. Nevertheless, the dependence of energy on atomic configuration can still be adequately learned without these strict requirements by using compressed sensing by way of coherent measurements using redundant function sets known as frames. We develop a particular frame constructed from the union of all occupancy-based cluster expansion basis sets. We illustrate how using this highly redundant frame yields sparse expansions of the configuration energy of complex oxide materials that are competitive and often surpass the prediction accuracy and sparsity of models obtained from standard cluster expansions. I. INTRODUCTIONThe Cluster Expansion Method (CEM), [1-3] has become a standard tool in computational thermodynamics of multi-component crystalline systems as an effective and efficient means to compute functions of atomic configuration. The CEM is used to represent a coarse-grained lattice model of materials properties as a function of the possible atomic configurations, i.e. the occupations of crystallographic sites. The most common use of the CEM involves the expansion of the formation energy of a particular multicomponent material system. A cluster expansion is fitted using formation energies for a set of representative structures calculated from first principles electronic structure methods, most often calculated with density functional theory (DFT). Well-converged cluster expansions fitted to DFT energies have been shown to give very accurate predictions of formation energy to within a few meV/atom. [3-5] A converged cluster expansion can subsequently be used in Monte Carlo simulations to compute thermodynamic properties, such as configuration entropy, [6, 7] phase diagrams, [8] ionic percolation,[9, 10] and short range order. [11,12] * †

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Short-range order in face-centered cubic VCoNi alloys

Cited by 38 publications

References 63 publications

Local order in AgAuCuPdPt high entropy alloy surfaces

Local order in AgAuCuPdPt high entropy alloy surfaces

Coupled Strengthening Effects by Lattice Distortion, Local Chemical Ordering, and Nanoprecipitates in Medium-Entropy Alloys

Sparse expansions of multicomponent oxide configuration energy using coherency & redundancy

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