Hydrogen can both move or pin dislocations in body-centered cubic metals

Area of Science:

• Materials Science
• Metallurgy
• Physical Chemistry

Background:

• Understanding hydrogen-metal interactions is crucial for a hydrogen economy.
• Discrepant findings exist regarding hydrogen's effect on dislocation mobility in BCC steels.

Purpose of the Study:

• To resolve the conflicting observations of hydrogen-induced dislocation mobility and pinning.
• To investigate the dynamic behavior of dislocations under hydrogen flux in BCC metals.

Main Methods:

• In-situ scanning electron microscopy with a custom experimental setup.
• Molecular dynamics simulations to model hydrogen-dislocation interactions.

Main Results:

• Observed initial hydrogen-induced dislocation motion at room temperature.
• Demonstrated subsequent dislocation pinning with sustained hydrogen flux.
• Simulations confirmed dislocation attraction to hydrogen flux and subsequent trapping-induced pinning.

Conclusions:

• Hydrogen's effect on dislocations is dynamic and depends on flux and trapping.
• Future studies must consider these distinct regimes for accurate hydrogen-defect interaction models.