# The influence of hydrogen core force shielding on dislocation junctions in iron

## TL;DR

This study investigates how hydrogen reduces dislocation core forces in iron, affecting junction strength and dislocation behavior, using a calibrated discrete dislocation dynamics model incorporating atomic-scale hydrogen effects.

## Contribution

The paper introduces a hydrogen-dependent core force into dislocation dynamics, calibrated at the atomic scale, to analyze hydrogen's influence on dislocation junctions in iron.

## Key findings

- Hydrogen reduces dislocation core energy and core force.
- Hydrogen strengthens binary junctions and promotes dislocation nucleation.
- Hydrogen core force shielding increases junction density and hardening.

## Abstract

The influence of hydrogen on dislocation junctions was analysed by incorporating a hydrogen dependent core force into nodal based discrete dislocation dynamics. Hydrogen reduces the core energy of dislocations, which reduces the magnitude of the dislocation core force. We refer to this as hydrogen core force shielding, as it is analogous to hydrogen elastic shielding but occurs at much lower hydrogen concentrations. The dislocation core energy change due to hydrogen was calibrated at the atomic scale accounting for the nonlinear inter-atomic interactions at the dislocation core, giving the model a sound physical basis. Hydrogen was found to strengthen binary junctions and promote the nucleation of dislocations from triple junctions. Simulations of microcantilever bend tests with hydrogen core force shielding showed an increase in the junction density and subsequent hardening. These simulations were performed at a small hydrogen concentration realistic for bcc iron.