Journal
ACTA MATERIALIA
Volume 199, Issue -, Pages 253-263Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2020.08.030
Keywords
Hydrogen embrittlement; Hydrogen diffusion; Fatigue; Microstructural traps; Coupled deformation-diffusion modelling
Funding
- Regional Government of Asturias [FC-GRUPIN-IDI/2018/000134]
- EPSRC [EP/R010161/1]
- UKCRIC Coordination Node, EPSRC [EP/R017727/1]
- IUTA [SV-19-GIJON-1-19]
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We investigate the influence of microstructural traps on hydrogen diffusion and embrittlement in the presence of cyclic loads. A mechanistic, multi-trap model for hydrogen transport is developed, implemented into a finite element framework, and used to capture the variation of crack tip lattice and trapped hydrogen concentrations as a function of the loading frequency, the trap binding energies and the trap densities. We show that the maximum value attained by the lattice hydrogen concentration during the cyclic analysis exhibits a notable sensitivity to the ratio between the loading frequency and the effective diffusion coefficient. This is observed for both hydrogen pre-charged samples (closed-systems) and samples exposed to a permanent source of hydrogen (open-systems). Experiments are used to determine the critical concentration for embrittlement, by mapping the range of frequencies where the output is the same as testing in inert environments. We then quantitatively investigate and discuss the implications of developing materials with higher trap densities in mitigating embrittlement in the presence of cyclic loads. It is shown that, unlike the static case, increasing the density of beneficial traps is a viable strategy in designing alloys resistant to hydrogen assisted fatigue for both closed- and open-systems. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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