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Ukai, Shigeharu*; Otsuka, Satoshi; Kaito, Takeji; Sakasegawa, Hideo*; Chikada, Nobuyoshi*; Hayashi, Shigenari*; Onuki, Somei*
Materials Science & Engineering A, 510-511, p.115 - 120, 2009/06
Times Cited Count：104 Percentile：96.42(Nanoscience & Nanotechnology)Oxide dispersion strengthened (ODS) ferritic steels, which are the most promising candidate materials for advanced fast reactor fuel elements, have exceptional creep strength at 973 K. The superior creep property of 9Cr-ODS ferritic steels is ascribed to the formation of a nonequilibrium phase, designated as the residual ferrite. The yield strength of the residual ferrite itself has been determined to be as high as 1360 MPa at room temperature from nanoindentation measurements. The creep strength is enhanced by minimizing the number of packet boundaries induced by the martensitic phase transformation. The creep strain occurs by sliding at weaker regions such as at the grain boundaries and packet boundaries. It is found that 9Cr-ODS ferritic steels behave as fiber composite materials comprising the harder residual ferrite and the softer tempered martensite.
Chikada, Nobuyoshi*; Hayashi, Shigenari*; Ukai, Shigeharu*; Kono, Yutaka*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
The mechanistic study was carried out on high-temperature strength of 9Cr-ODS ferritic steel that has a duplex microstructure of tempered martensite and residual-alpha ferrite. Microstructure characterizations were performed by micro and nano-hardness tests and microstructure observations after normalizing and tempering. Resistance to tempering was shown to increase with volume fraction of residual-alpha ferrite. This result is consistent with creep rupture test result. Individual strength of tempered martensite and residual-alpha ferrite was estimated from nano-hardenss and inter-particle spacing. In the presentation, discussion will be performed on the mechanism of residual-alpha ferrite formation as well as the effect of residual-alpha ferrite on high-temperature strength improvement.
Chikada, Nobuyoshi*; Hayashi, Shigenari*; Ukai, Shigeharu*; Onuki, Somei*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
The hardness measurement by nanoindentation and microstructure analysis by TEM revealed that the tempering softening resistance of 9Cr-ODS ferritic steels is owing to the formation of ultrafine grains in residual ferrite phase.
Chikada, Nobuyoshi*; Hayashi, Shigenari*; Ukai, Shigeharu*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
It may be possible that the high-temperature strength of 9Cr-ODS ferritic/martensitic steel is largely improved by the formation of ultra-fine residual-alpha phase. This study discussed the correlation between ultra-fine residual-alpha formation and mechanical strength in ODS ferritic steel.
Chikada, Nobuyoshi*; Hayashi, Shigenari*; Ukai, Shigeharu*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
It may be possible that high-temperature strength of 9Cr-ODS ferritic/martensitic steel is largely improved by the ultra-fine residual-alpha phase. This study discussed the correlation between the ultra-fine residual alpha phase formation and mechanical strength.
Ukai, Shigeharu*; Chikada, Nobuyoshi*; Hayashi, Shigenari*; Onuki, Somei*; Kaito, Takeji; Otsuka, Satoshi
no journal, ,
The 9Cr-ODS ferritic steel for fast reactor fuel cladding tube has been developed by JAEA. This study discussed the mechanism of high-temperature strength improvement produced by feeritic/martensitic duplex structure.
Chikada, Nobuyoshi*; Hayashi, Shigenari*; Ukai, Shigeharu*; Otsuka, Satoshi; Kaito, Takeji
no journal, ,
no abstracts in English
