Radiation damage of ultrafine grained and nanocrystalline 304 austenitic stainless steel subjected to heavy ion irradiation

Oxide dispersion strengthened (ODS) steels with nanoscale structures have significant potential as advanced structural materials in modern nuclear reactors due to their enhanced irradiation resistance. This study investigates La-doped ultrafine-grained (UFG) and nanocrystalline (NC) 304 austenitic stainless steels (304SS), emphasizing their improved irradiation resistance resulting from grain refinement and the formation of La-rich nanoparticles along grain boundaries. Commercial coarse-grained (CG) 304SS was studied as a baseline for comparison. The materials were irradiated with 6 MeV Au ions at 500 °C, reaching a displacement damage level of 220 displacements per atom (dpa). Microstructural evolution post-irradiation was characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Additionally, nanoindentation tests were conducted to measure the nanohardness and modulus of both pristine and irradiated samples. Furthermore, detailed analysis of microstructural changes and elemental segregation induced by Au-ion irradiation was compared with previous results from Fe-ion irradiation under comparable conditions. • La-doped oxide dispersion strengthened 304 steels exhibited outstanding Au-ion irradiation resistance. • Irradiation induced grain growth and softening in ultrafine-grained and nanocrystalline steels . • Au-ion irradiation induced much lower swelling rate and suppressed elemental segregation than Fe-ion irradiation in steels.