Transmission Electron Microscopy Characterization of Grain Structure and Nanoparticles of 15-15Ti ODS Austenitic Steel

Due to their excellent corrosion resistance and high temperature mechanical properties, the 15-15Ti austenitic stainless steels have been selected as a candidate cladding material for the sodium-cooled fast reactor. Its high-temperature mechanical strength and resistance to irradiation swelling can be enhanced by oxide dispersion strengthening (ODS). In this study, 15-15Ti ODS austenitic steel was manufactured by mechanical alloying and forging processes. The 15-15Ti steel manufactured following the same procedures without additions of ODS particles was chosen as the control sample material. The microstructure of the sample was characterized by multiple transmission electron microscopy (TEM) techniques. The dispersion characteristics and strengthening mechanism of oxide particles in the ODS austenitic stainless steel were comprehensively investigated. The special distribution of the oxide dispersion particles was generally uniform, however, a clustering tendency was also identified. The average size of the particles was estimated to be (9.97±0.04) nm, the average distances between the particles was (17.25±0.68) nm, and the number density was about 5.32×1022 m-3. The pinning effect of oxide particles on dislocations was observed in the ODS samples through TEM bright field imaging. Two oxides were revealed in the ODS sample by scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray (EDX) spectroscopy, which consists a small proportion of Al2O3 particles and a large proportion of Y4Zr3O12 particles. High-resolution transmission electron microscopy characterizations reveal signs of a coherent or semi-coherent interface between the second-phase particle and the 15-15Ti matrix, and a few particles appear around amorphous interfaces. © 2024 Cailiao Daobaoshe/ Materials Review. All rights reserved.