An interplay between a hydrogen atmosphere and dislocation characteristics in BCC Fe from time-averaged molecular...

Area of Science:

• Materials Science
• Metallurgy
• Computational Materials Science

Background:

• The influence of hydrogen on dislocations is crucial for understanding hydrogen embrittlement but remains poorly understood.
• Existing continuum models neglect hydrogen's effect on dislocation core energies, and atomistic simulations omit hydrogen motion, preventing atmosphere formation analysis.
• Previous research has predominantly focused on face-centered-cubic metals, with limited investigation into body-centered-cubic systems.

Purpose of the Study:

• To investigate the impact of hydrogen on dislocation energies, including core and elastic energies, and dislocation-dislocation interactions.
• To explore hydrogen atmosphere formation around dislocations in body-centered-cubic iron.
• To assess the validity of assuming isotropic elasticity in discrete dislocation dynamics studies of hydrogen-dislocation interactions.

Main Methods:

• Time-averaged molecular dynamics simulations were employed to study hydrogen-dislocation interactions in body-centered-cubic iron.
• Simulations considered various dislocation character angles to capture diverse interaction scenarios.
• Dislocation energies were calculated and analyzed to quantify the effects of hydrogen presence.

Main Results:

• Hydrogen atmosphere formation around dislocations was observed and confirmed.
• Hydrogen was found to reduce dislocation core energies.
• Hydrogen's effect on elastic energies and dislocation-dislocation interactions varied with dislocation character angle, showing both increases and decreases.
• Isotropic elasticity models can approximate simulation results if elastic constants are not constrained.

Conclusions:

• Hydrogen significantly influences dislocation energetics in body-centered-cubic iron, impacting core, elastic, and interaction energies.
• The findings provide critical insights into the mechanisms of hydrogen embrittlement.
• This work lays the groundwork for more accurate computational modeling of hydrogen-metal interactions.