Fundamental study for nano-particle dispersion strengthened austenitic steel creation, 3; Characterization of complex oxide precipitated during heat treatment

Oka, Hiroshi*   ; Watanabe, Masashi*  ; Hashimoto, Naoyuki*; Kinoshita, Hiroshi*; Shibayama, Tamaki*; Onuki, Somei*; Yamashita, Shinichiro   ; Otsuka, Satoshi   

In this study, ODS austenitic stainless steels based on an advanced SUS316 steel has been developed by mechanically alloying (MA) and hot extrusion with the addition of minor alloying elements. The chemical composition of ODS316 is Fe-16Cr-13Ni-0.35YO-0.1Ti-0.6Hf. Thin foils for transmission electron microscope (TEM) examination were prepared with electro-polishing. HRTEM and EDS were used for characterization of oxide particles in ODS-316, especially precipitation behavior and chemical composition before and after heat treatment. Microstructural observation revealed that the ODS316 has grains of 0.5-1m in diameter and complex oxides (Y-Ti-Hf-O) distributed in matrix. The strain contrast was observed around oxide particles, suggesting coherency of oxide particles. HR-TEM observation revealed that a part of faceted particles have coherency. Interface between matrix and oxide particles after heat treatment was also carefully investigated.