From sink bias to void swelling in irradiated structural materials

Void swelling is generally observed at 0.3 - 0.6 of the melting temperature due to high levels of particle radiation, which leads to considerable volumetric changes and degraded mechanical properties in irradiated materials. The bias model is postulated as the driving force of this phenomenon. There are three long-standing and critical issues in the void swelling phenomenon. First, dislocation loop bias in irradiated materials significantly influences void swelling, but quantifying this bias is challenging due to complex interactions with point defects. Second, void swelling is generally found higher in fcc (face-centered cubic) materials compared to bcc (body-centered cubic) materials, but the underlying mechanism remains ambiguous. Third, voids have been regarded as neutral sinks in conventional studies, while both theoretical and experimental findings suggest that voids prefer to absorb mobile interstitials over vacancies. This dissertation employed a recently developed atomistic kinetic Monte Carlo (AKMC) approach to determine the bias of various point defect sinks in irradiated metals, and subsequently provide explanations for these three issues. Dislocation loop bias in bcc iron is found lower than that of straight dislocations, and the swelling rate prediction in irradiated Fe shows an agreement with experimental observations while considering both dislocation and loop bias. In fcc Cu, stacking fault tetrahedra (SFTs) are found to significantly increase the swelling rate. Additionally, voids with small sizes are proven biased sinks in Fe, Cu, and Ni. These findings will significantly contribute to the understanding of swelling phenomena in irradiated structural materials.