Hydrogen modified dislocation loop types and shapes in irradiated iron

Dislocation loops are one type of irradiation defects that severely degrade the mechanical properties of nuclear materials. In this study, we found that hydrogen atoms in irradiation environment significantly modify the loop properties including loop types and shapes during in-situ hydrogen irradiation. <100> loops have been energetically stable from 300 °C in H⁺ irradiated iron whereas the stability of <100> loops is delayed until 500 °C in Fe⁺ irradiated iron. Meanwhile, both <100> loops and 1/2<111> loops exhibit polygonal shapes with sharp corners at 400 °C after H⁺ irradiation, similar to loops predicted at 900 °C without hydrogen. Our results highlight the importance of considering the hydrogen effects in dislocation loop evolution and stability.