Stress-induced anisotropic diffusion in alloys: Complex Si solute flow near a dislocation core in Ni

Garnier, Thomas; Manga, Venkateswara Rao; Trinkle, Dallas R.; Nastar, Maylise; Bellon, Pascal

doi:10.1103/physrevb.88.134108

Cited by 52 publications

(57 citation statements)

References 33 publications

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“…The SelfConsistent Mean-Field method (SCMF) is a promising path to provide kinetic properties for complicated systems. First developed for vacancy-mediated diffusion in BCC lattices 29 , it has since then been extended to various structures [30][31][32][33] and migration mechanisms [34][35][36] . Basically, the SCMF method uses linear response theory to compute the flux resulting from a uniform driving force, which allows for identification of the Onsager matrix.…”

Section: Introductionmentioning

confidence: 99%

Transport properties in dilute UN(X) solid solutions (X=Xe,Kr)

et al. 2016

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Uranium nitride (UN) is a candidate fuel for current GEN III fission reactors, for which it is investigated as an accident-tolerant fuel, as well as for future GEN IV reactors. In this study, we investigate the kinetic properties of gas fission products (Xe and Kr) in UN. Binding and migration energies are obtained using density functional theory, with an added Hubbard correlation to model f -electrons, and the Occupation Matrix Control scheme to avoid metastable states. These energies are then used as input for the Self-Consistent Mean Field method which enables to determine transport coefficients for vacancy-mediated diffusion of Xe and Kr on the U-sublattice. The magnetic ordering of the UN structure is explicitly taken into account, for both energetic and transport properties. Solute diffusivities are compared with experimental measurements and the effect of various parameters on the theoretical model is carefully investigated. We find that kinetic correlations are very strong in this system, and that despite atomic migration anisotropy, macroscopic solute diffusivities show limited anisotropy. Our model indicates that the discrepancy between experimental measurements probably results from different irradiation conditions, and hence different defect concentrations.

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Section: Introductionmentioning

confidence: 99%

Transport properties in dilute UN(X) solid solutions (X=Xe,Kr)

et al. 2016

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“…A complete calculation of attempt frequency requires the computation of the full force-constant matrix. Approximate values of the force-constant matrix have often been used but the convergence of attempt frequency is not straightforward 25 , such that one cannot estimate the accuracy of these approximations a priori. For 230 solutes divided among 7 solvents with various crystallographic structures, variation of individual mechanisms attempt frequencies with respect to the isolated vacancy jump are all within a factor of 0.13-2.04 39 such that kinetic correlations are almost entirely monitored by migration ener-gies, except at high temperatures.…”

Section: A Density-functional Theory Calculationsmentioning

confidence: 99%

“…The self-consistent mean field method (SCMF) has seen growing interest and development in the last fifteen years [22][23][24][25][26][27][28] . For solute and point-defect diffusion, it provides a general link between the atomic scale (individual jump rates) and the macroscopic scale (transport coefficients).…”

Section: B Transport Coefficients Frameworkmentioning

confidence: 99%

“…The SCMF method provides a formal link between individual jump processes at the atomic scale and long range diffusion which is responsible for microstructure evolution. This method of growing interest has been applied to various crystal structures, various diffusion mechanisms, strained systems, and non-homogeneous driving forces [22][23][24][25][26][27][28] . In this work, the DFT+U+OMC and the SCMF method are applied to understand the mobility and long range diffusion of carbon and oxygen in the UN lattice.…”

Section: Introductionmentioning

confidence: 99%

“…The self-consistent mean-field (SCMF) method allows to compute transport coefficients (which control the kinetic properties of the system) from atomic jump rates computed with DFT [22][23][24][25][26][27][28] . It uses a thermal average of a microscopic master equation to compute the deviation of the probability of each configuration (with respect to equilibrium) under a chemical potential gradient.…”

Section: Introductionmentioning

confidence: 99%

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Transport properties of C and O in UN fuels

et al. 2017

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Uranium nitride fuel is considered for fast reactors (GEN-IV generation and space reactors) and for light water reactors as a high-density fuel option. Despite this large interest, there is a lack of information about its behavior for in-pile and out-of-pile conditions. From the present literature, it is known that C and O impurities have significant influence on the fuel performance. Here, we perform a systematic study of these impurities in the UN matrix using electronic-structure calculations of solute-defect interactions and microscopic jump frequencies. These quantities were calculated in the DFT+U approximation combined with the occupation matrix control scheme, to avoid convergence to metastable states for the 5f levels. The transport coefficients of the system were evaluated with the self-consistent mean-field theory. It is demonstrated that carbon and oxygen impurities have different diffusion properties in the UN matrix, with O atoms having a higher mobility, and C atoms showing a strong flux coupling anisotropy. The kinetic interplay between solutes and vacancies is expected to be the main cause for surface segregation, as incorporation energies show no strong thermodynamic segregation preference for (001)-surfaces compared with the bulk.

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Autonomous Repair Mechanism of Creep Damage in Fe-Au and Fe-Au-B-N Alloys

Zhang

Kwakernaak

Tichelaar

et al. 2015

Metall Mater Trans A

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The autonomous repair mechanism of creep cavitation during high-temperature deformation has been investigated in Fe-Au and Fe-Au-B-N alloys. Combined electron-microscopy techniques and atom probe tomography reveal how the improved creep properties result from Au precipitation within the creep cavities, preferentially formed on grain boundaries oriented perpendicular to the applied stress. The selective precipitation of Au atoms at the free creep cavity surface results in pore filling, and thereby, autonomous repair of the creep damage. The large difference in atomic size between the Au and Fe strongly hampers the nucleation of precipitates in the matrix. As a result, the matrix acts as a reservoir for the supersaturated solute until damage occurs. Grain boundaries and dislocations are found to act as fast transport routes for solute gold from the matrix to the creep cavities. The mechanism responsible for the self-healing can be characterized by a simple model for cavity growth and cavity filling.

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Stress-induced anisotropic diffusion in alloys: Complex Si solute flow near a dislocation core in Ni

Cited by 52 publications

References 33 publications

Transport properties in dilute UN(X) solid solutions (X=Xe,Kr)

Transport properties in dilute UN(X) solid solutions (X=Xe,Kr)

Transport properties of C and O in UN fuels

Autonomous Repair Mechanism of Creep Damage in Fe-Au and Fe-Au-B-N Alloys

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