Fabrication and evaluation of ODS ferritoc mother tubes for FBR fuel cladding tubes; Evaluation of the mechanical properties and recrystallization

Okuda, Takanari*; Harada, Makoto*; not registered

Micro-crystal direction analysis by electron back scattering pattern, oxide particle dispersion parameter analysis and the mechanical properties were evaluated, The main results were as follows: (1)Microstructure. Although the ferritic steels were equi-axed grains in the transverse direction of tube, the aspect ratio increased with Ti and YO content of the steel. The 20% cold worked tubes were high densities of dislocation. The martensitic steels were equi-axed grains both in transverse and longitudinal directions. M91 steel was a ferritic structure and low dislocation density. M92 steel was a full martensitic. (2)Tensile properties in the circumferential direction. The uniform elongation of ferritic steel was lowest at 400 C. In the martensitic steels, M92 steel with high Ti content showed a high strength and good ductility. (3)Creep rupture strength. For the ferritic steels, the internal creep rupture strength at 700 C because higher as Ti and YO content increased. The martensitic steels showed high creep rupture strength by controlling the addition of Ti and YO. (4)Recrystallizaiton analysis of ferritic steels by EBSP. By the sequence of cold rolling and heat treatment, recrystallization became difficult. For a stable direction, 110 tends to form a strong texture. (5)Evaluation for distribution parameter of oxide particles. The threshold stress, which was calculated by the combination of the volume fraction of dispersoids and image analysis, exhibited reasonable results.