Mechanical and helium swelling responses of K-RAFM steels to Fe ion irradiation and helium implantation

Abstract

This study explores the effects of Fe ion irradiation and helium implantation on the mechanical and microstructural behaviors of K-RAFM steels. Through micropillar compression tests, we observed irradiation hardening, which manifested as an increase in strength and a decrease in strain bursts in the irradiated specimens. This change in deformation behavior indicates the impact of radiation-induced defects on dislocation dynamics. Helium implantation resulted in the formation of surface steps and, as shown by nanoindentation mapping, led to a localized increase in hardness, highlighting the significant influence of helium on mechanical properties. Microstructural examination revealed the steel's tempered martensitic structure and pointed to the importance of M23C6 and MX precipitates in modulating the effects of irradiation. Notably, K-RAFM steels showed a diminished extent of irradiation hardening, which can be attributed to the higher fraction of MX precipitates serving as effective trapping sites for point defects. Understanding how microstructural features influence mechanical performance in K-RAFM steels assists in steering the creation of materials tailored to improve radiation resistance in nuclear environments.

Keywords

• RAFM steels
• Irradiation hardening
• Helium swelling