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Site stability and pipe diffusion of hydrogen under localised shear in aluminium

Wang, Yu and Connétable, Damien and Tanguy, Döme Site stability and pipe diffusion of hydrogen under localised shear in aluminium. (2019) Philosophical Magazine, 99 (10). 1184-1205. ISSN 1478-6435

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Official URL: https://doi.org/10.1080/14786435.2019.1576935

Abstract

This paper studies the effect of a plastic shear on the tetrahedral vs. octahedral site stability for hydrogen, in aluminium. Based on Density Functional Theory calculations, it is shown that the tetrahedral site remains the most stable site. It transforms into the octahedral site of the local hexagonal compact structure of the intrinsic stacking fault. The imperfect stacking is slightly attractive with respect to a regular lattice site. It is also shown that the shearing process involves a significant decrease of the energetic barrier for hydrogen jumps, at half the value of the Shockley partial Burgers vector, but not in the intrinsic stacking fault. These jumps involve a displacement component perpendicular to the shearing direction which favours an enhancement of hydrogen diffusion along edge dislocation cores (pipe diffusion). The magnitude of the boost in the jump rate in the direction of the dislocation line, according to Transition State Theory and taking into account the zero point energy correction, is of the order of a factor 50, at room temperature. First Passage Time Analysis is used to evaluate the effect on diffusion which is significant, by only at the nanoscale. Indeed, the common dislocation densities are too small for these effects (trapping, or pipe diffusion) to have a signature at the macroscopic level. The observed drop of the effective diffusion coefficient could therefore be attributed to the production of debris during plastic straining, as proposed in the literature.

Item Type:Article
HAL Id:hal-02285882
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Other partners > Université Claude Bernard-Lyon I - UCBL (FRANCE)
Laboratory name:
Funders:
Agence Nationale de la Recherche - ANR - HPC resources
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Deposited By: Yves MOMBOISSE
Deposited On:18 Nov 2019 10:45

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