Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Tokunaga, Tomonori*; Watanabe, Hideo*; Yoshida, Naoaki*; Nagasaka, Takuya*; Kasada, Ryuta*; Lee, Y.-J.*; Kimura, Akihiko*; Tokitani, Masayuki*; Mitsuhara, Masatoshi*; Hinoki, Tatsuya*; et al.
Journal of Nuclear Materials, 442(1-3), p.S287 - S291, 2013/11
Times Cited Count：6 Percentile：49.64(Materials Science, Multidisciplinary)Mitsuhara, Masatoshi*; Harada, Erika*; Yamasaki, Shigeto*; Ikeda, Kenichi*; Hata, Satoshi*; Nakashima, Hideharu*; Otsuka, Satoshi; Kaito, Takeji
Kashika Joho Gakkai-Shi, 31(122), p.98 - 103, 2011/07
no abstracts in English
Mitsuhara, Masatoshi*; Ikeda, Kenichi*; Hata, Satoshi*; Nakashima, Hideharu*; Wakai, Takashi
Kyushu Daigaku Cho Koatsu Denkenshitsu Kenkyu Hokoku, 32, 2 Pages, 2008/08
no abstracts in English
Mitsuhara, Masatoshi*; Ikeda, Kenichi*; Hata, Satoshi*; Nakashima, Hideharu*; Wakai, Takashi
Materia, 47(6), P. 301, 2008/06
no abstracts in English
Mitsuhara, Masatoshi*; Ikeda, Kenichi*; Hata, Satoshi*; Nakashima, Hideharu*; Wakai, Takashi
Materia, 46(12), P. 800, 2007/12
High Cr ferritic steels bearing V have high creep strength due to the precipitation hardening. In order to enhance the efficiency of the precipitation hardening, the elemental components, shape and distribution of the precipitates should be comprehended. In this study, we investigated that of the precipitates in the 10Cr ferritic steel bearing V using the STEM-EDS analysis and the three-dimensional electron tomography (3D-ET) observation. The two types of precipitates on the lath boundaries could be observed, which were lump-shaped precipitates and film-shaped precipitates. They had the different elemental component. From the 3D-ET observation, it revealed that the film-shaped precipitates covered the lath boundary widely. Therefore, the film-shaped precipitates are expected to be effective for the stabilization of martensitic microstructure during the creep deformation.
Mitsuhara, Masatoshi*; Yoshida, Yu*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
Kyushu Daigaku Cho Koatsu Denkenshitsu Kenkyu Hokoku, 31, p.78 - 79, 2007/00
The effects of V and Nb on creep strength of high Cr ferritic steel were investigated based on the observation results using STEM. As a result, it is clarified that Nb contributes to the improvement of creep strength by encumber the movement of the lath boundary by fine dispersed precipitation as MX particles and V contributes as film precipitation on the lath boundary.
Yoshida, Yu*; Mitsuhara, Masatoshi*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
Tainetsu Kinzoku Zairyo Dai-123-Iinkai Kenkyu Hokoku, 47(10), p.109 - 113, 2006/07
This paper studies the influence of V and Nb on the creep strength and behavior of high Cr ferritic steels. A series of creep tests of 11 steels having various V and Nb contents is conducted. The test results are analyzed by omega-method and the microstructures of the damaged specimens are examined by EBSP. As a result, it is shown that omega-method gives good prediction of creep lives of the steels and that the influence of V and Nb on the omega-parameters is significant. In addition, it is clarified that the martensitic microstructure of the steels depends upon Nb content.
Nakashima, Hideharu*; Ikeda, Kenichi*; Yoshida, Fuyuki*; Otsuka, Satoshi; Ukai, Shigeharu
JNC TY9400 2004-019, 56 Pages, 2004/08
JNC-TY9400-2004-019.pdf:5.22MB
The grian boundary structure of Oxide Dispersion Strengthened (ODS) steel was analysed. Based on the analysis results, the grain boundary control procedure for creep strength improvement was discussed.
Yoshida, Fuyuki*; Nakashima, Hideharu*
PNC TJ9606 97-001, 43 Pages, 1997/03
None
Yoshida, Fuyuki*; *; *; Nakashima, Hideharu*; *
PNC TJ9606 95-002, 62 Pages, 1995/04
In order to clarify the origin of strength anisotropy in ODS ferritic steel with Y
O
particles at high temperatures, a threshold stress measured by stress abruptly loading test (SAL test) were compared with the Orowan and the void-hardening stresses calculated from dispersion parameters and subjected to the high-temperature compression test at temperature from 600 to 700 
C and at strain rates from 1
10
to 110
s
, and the effect of grain-boundary sliding on the high-temperature strength was clarified. The results are summarized as follows. (1) The Orowan stress and the void-hardening stress calculated from dispersion parameters approximately agreed with the threshold stress obtained by SAL test. In addition, as the time under load elapsed, the transition of the threshold stress obtained by SAL test was observed, it is concluded that the originating mechanism of the threshold stress in ODS ferritic steel is the Srolovitz's one (2) The grain-boundary sliding was clearly observed for grain boundaries inclined by 45 to the stress axis. The flow stress was changed significantly by aspect ratio of grain size. Therefore, it is concluded that the strength anisotropy in ODS ferritic steel induces the grain-boundary sliding behaviour.
Nakashima, Hideharu*; *; *; Yoshida, Fuyuki*; *
PNC TJ9606 94-001, 59 Pages, 1994/03
In order to clalify the origin of strength anisotropy in ODS ferritic steel with YO particles at high temperatures, the threshold stress was measured by the stress abruptly loading test at 650 C and the effect of grain-boundary sliding on the high-temperature strength was clarified. The results are summalized as follows. (1)The threshold stress obtained by the stress abruptly loading test decreased from the Orowan stress to the void-hardening stress as the time under load elapsed. This behavior is well explained by the attractive interaction between dislocations and particles. (2)The grain-boundary sliding was clearly observed for grain boundaries in-clined by 45 to the stress axis. The threshold stress for the high-temperature deformation accompanying grain-boundary sliding agreed with the threshold stress obtained by the stress abruptly loading test. Therefore, it is considered that grain interior deformation induces the grain-boudary sliding of the ODS ferritic steel at high temperatures.
Nakashima, Hideharu*; *
PNC TJ9606 93-001, 36 Pages, 1993/03
It has been examined about mechanisms of strength anisotropy and ductility dip of ODS ferritic steel induded with YO particles at high temperatures. The results are summarized as follows. (1)Above 650C, 0.2% proof stress measured by tensile test and axial cleep rupture strength agree with the threshold stress for dislocation motion evaluated by the theory of the dispersion strengthening. But the bi-axial creep rupture stress is smaller than the threshold stress. It is presumed that grain boundaries in transverse section of cladding tube slide by the hoop stress below the threshold stress. It is considered that the strength anisotropy comes from an elongated grains formed by fabrication. (2)The ductility decreases in two different temperature ranges which are around 600C and 1100C respectively. The ductility-minimum temperature in the lower temperature range is independent of the strain rate in a high strain rate range, whereas that temperature is dependent on the strain rate in a low strain rate range. The reason why the strain rate dependence of the ductility-minimum temperature is different between high and low strin rate ranges has not been clarified. But it is suggested that the dip in the lower temperature range should be related to the grain boundary sliding and the grain-boundary precipitation. In the higher ductility-dip temperature range, this alloy has an 
-
duplex structure. Therefore, it is considered that the ductility dip arises from the concentration of the deformation in phase.
Nb added 12Cr-1Mo steelsYoshida, Yu*; Mitsuhara, Masatoshi*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
no journal, ,
no abstracts in English
Yoshida, Yu*; Mitsuhara, Masatoshi*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
no journal, ,
no abstracts in English
Yoshida, Yu*; Mitsuhara, Masatoshi*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
no journal, ,
no abstracts in English
Yoshida, Yu*; Mitsuhara, Masatoshi*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
no journal, ,
no abstracts in English
Mitsuhara, Masatoshi*; Yoshida, Yu*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
no journal, ,
no abstracts in English
Mitsuhara, Masatoshi*; Yoshida, Yu*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
no journal, ,
The effect of V and Nb on creep strengthening was studied in 10% Cr steels. In a steel added 0.06% V where no particles were observed in the lath, creep strength was slightly increased, indicating that it was not strengthened by particle hardening effect in the lath. Lump-shaped precipitates and film-shaped precipitates including Cr and V, which were observed on lath boundaries in the steel added V, are expected to inhibit the lath boundaries from migrating. This inhibition is the mechanism of the improvement in the steel added V. In the case of steels added Nb individually, creep strength was found to be increased by dispersion hardening due to fine precipitates in the lath. These results revealed that V and Nb have each role to improve creep strength. In steels added both V and Nb, the effect on creep strength was expressed by the sum of the effects due to each element, which were the retardation of the lath boundary migrations and the pinning of the dislocations in the lath.
Mitsuhara, Masatoshi*; Yoshida, Yu*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
no journal, ,
no abstracts in English
Mitsuhara, Masatoshi*; Yoshida, Yu*; Ikeda, Kenichi*; Nakashima, Hideharu*; Wakai, Takashi
no journal, ,
no abstracts in English
