Modeling Dislocation-Mediated Hydrogen Transport and Trapping in Face-Centered Cubic Metals

Abstract

The diffusion of hydrogen in metals is of interest due to the deleterious influence of hydrogen on material ductility and fracture resistance. It is becoming increasingly clear that hydrogen transport couples significantly with dislocation activity. In this work, we employ a coupled diffusion-crystal plasticity model to incorporate hydrogen transport associated with dislocation sweeping and pipe diffusion in addition to standard lattice diffusion. Moreover, we consider generation of vacancies via plastic deformation and stabilization of vacancies via trapping of hydrogen. The proposed hydrogen transport model is implemented in a physically-based crystal viscoplasticity framework to model the interaction of dislocation substructure and hydrogen migration. In this study, focus is placed on hydrogen transport and trapping within the intense deformation field of a crack tip plastic zone. We discuss the implications of the model results in terms of constitutive relations that incorporate hydrogen effects on crack tip field behavior and enable exploration of hydrogen embrittlement mechanisms.

Effect of Slow Strain Rates on the Hydrogen Migration and Different Crack Propagation Modes in Pipeline Steel

“…[ 46,47 ] The movement of the dislocations transports weakly trapped hydrogen and lattice hydrogen toward the regions with high stress concentration, such as grain boundaries, crack tips, and second‐phase interfaces. [ 48,49 ] Wang et al [ 24 ] reported the increased peak hydrogen concentration with decreasing crosshead speed. Meanwhile, Hashimoto et al [ 50 ] found a linear positive correlation between the engineering strain and hydrogen trap density.…”

Hydrogen Embrittlement as a Conspicuous Material Challenge─Comprehensive Review and Future Directions

“…As the relationship between H and plasticity becomes more intricate, dislocation-based plasticity models, particularly those using a crystal plasticity approach coupled with H kinetics, are being explored. 799,800 These models account for vacancy generation and dislocation-mediated H transport, moving toward a more comprehensive simulation of H-accelerated FCG.…”

“…Crystal plasticity approaches could be the key to understand these processes. 799 A possible mechanism that is not commonly addressed but requires further understanding is H pipe diffusion along dislocation cores, which has been proved by DFT calculations for some metals. However, the process was regarded secondary in iron 848 or at a macroscopic level.…”

“…Subsequent models have integrated stress and plasticity effects on H distribution and their influence on elasto-plastic deformation. , Cohesive zone models were coupled with H diffusion analysis and trapping kinetics, capable of simulating the frequency dependence of H-related FCG rate. As the relationship between H and plasticity becomes more intricate, dislocation-based plasticity models, particularly those using a crystal plasticity approach coupled with H kinetics, are being explored. , These models account for vacancy generation and dislocation-mediated H transport, moving toward a more comprehensive simulation of H-accelerated FCG.…”

Modeling hydrogen dragging by mobile dislocations in finite element simulations

“…This approach was applied to the simulation of hydrogen repartition ahead a crack tip in small scale yielding with isotropic elastoplastic material, as in previous works [10,11,31], they showed through a parametric study the effect of the hydrogen transport by dislocation both for bcc and fcc materials, which permits to improve the simulation of hydrogen transport. This approach has been extended to crystal plasticity scale [32,33] to add the influence of polycrystalline texture on the overall hydrogen transport.…”