Irradiation-induced microstrain and dislocation density in additively manufactured 316H stainless steel

This study investigated the response of additively manufactured (AM) 316H stainless steel (SS) compared to its conventionally manufactured counterpart under simulated irradiation conditions. We irradiated both types of steels with 0.5 MeV H + ions at room temperature and analyzed their microstructural and mechanical properties. X-ray diffraction revealed higher initial dislocation densities in AM SS due to its fabrication process. Interestingly, at lower irradiation doses (0.6 dpa), the AM SS showed a decrease in microstrain, while the conventional SS showed an increase. This suggests differing defect annihilation mechanisms. At 6.0 dpa, AM SS exhibited a rise in mi- crostrain and dislocation density, potentially due to saturation effects. Conversely, conventional SS showed a decrease, possibly indicating disordering from the irradiation. Microhardness measure- ments supported these findings, with AM SS displaying a more gradual response compared to the pronounced hardening and softening observed in conventional SS. Tensile testing revealed lower hardening and strength in irradiated AM SS compared to its pristine state. Scanning electron mi- croscopy showed contrasting fracture behavior between the two steel types, with AM SS exhibiting less embrittlement despite its higher initial hardness. Overall, AM SS demonstrated superior mi- crohardness and microstructural integrity after irradiation, suggesting its potential for applications in harsh irradiated environments.