Effect of zirconium on the microstrusture and mechanical properties of high-Cr ODS ferritic steels

高クロムODSフェライト鋼の組織と強度特性に及ぼすジルコニウムの影響

Dou, P.*; 笠田 竜太*; 木村 晃彦*; 奥田 隆成*; 井上 賢紀 ; 鵜飼 重治*; 大貫 惣明*; 藤澤 敏治*

Dou, P.*; Kasada, Ryuta*; Kimura, Akihiko*; Okuda, Takanari*; Inoue, Masaki; Ukai, Shigeharu*; Onuki, Somei*; Fujisawa, Toshiharu*

It is well known that the morphologies and coherency of nano-sized oxide particles have important effect on the strength of oxide dispersion strenthened(ODS) steel, and some minor elements are effective for achieving fine dispersion of oxide particles. The effect of zirconium is studied in the present research. The nano-mesoscopic structure and mechanical properties of newly-developed high Cr ODS ferritic steels with(SOC-14) and without zirconium(SOC-9) have been characterized by High Resolution Transmission Electron Microscopy(HRTEM), diffraction contrast technique and tensile tests. For SOC-14, the number density of oxide particles increases and their radii decrease, and the tensile strength at room temperature and 700C increases considerably, relative to SOC-9. The oxide particles in SOC-9 are mainly composed of Y-Al-O complex oxide, while the oxide particles in SOC-14 are composed of Y-Zr-O, Y-Al-O and Y-Ti-O complex oxides. The size dependence of coherecy of oxide particles was determined. The misfit strain was measured. The strengthening mechanism is discussed based on the character and morphology of oxide particles.