A study of helium bubble facetation in bcc iron through molecular dynamics

ZY Ming and Z Chen and ZF Wang and Q Xiong and Z Liu and C Yin and SF Mao and MY Ye, SCRIPTA MATERIALIA, 267, 116823 (2025).

DOI: 10.1016/j.scriptamat.2025.116823

Helium (He) bubble facetation is a widely observed phenomenon in neutron or ion irradiation experiments of iron (Fe) and its alloys. However, the underlying mechanism of bubble facetation remains unclear. In this research, molecular dynamics (MD) simulations are performed to study bubble facetation and the effects of temperature as well as bubble pressure (helium-to-vacancy ratio, He/V ratio) on facetation. The results give the dynamic evolution pictures of He bubble facetation at different temperatures. The process of facetation suggests that a spherical-faceted transition temperature of He bubble exists, which is consistent with experimental observations. Further analysis indicates that facets with higher surface energy emerge as intermediate states during facetation. This mechamism may explain why the bubble facetation predominantly occurs at elevated temperature. Additionally, simulation results related to He/V ratio suggest that increased adatom migration barrier induced by bubble pressure would significantly suppress bubble facetation.

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