ALLOYING DESIGN OF OXIDE DISPERSION-STRENGTHENED FERRITIC STEEL FOR LONG-LIFE FBRS CORE MATERIALS

Oxide dispersion strengthened (ODS) ferritic steels with excellent swe lling resistance and superior high temperature strength are prospectiv e cladding materials for advanced fast breeder reactors. The addition of Ti in 13Cr-3W ODS ferritic steels improved the high temperature str ength remarkably by the formation of uniformly distributed ultra-fine oxide particles. ODS ferritic steels have a bamboo-like grain structur e and a strong deformation texture. The decrease of creep rupture stre ngth in the bi-axial direction compared to the uni-axial direction is attributed mainly to this unique bamboo grain structure. Nearly equiva lent creep rupture strength for both bi-axial and uni-axial direction was successfully attained by introducing the alpha to gamma transforma tion in ODS martensitic steel.