Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Kasahara, Shigeki; Chimi, Yasuhiro; Nishiyama, Yutaka; Kitsunai, Yuji*; Chatani, Kazuhiro*; Koshiishi, Masato*
no journal, ,
Austenitic stainless steel irradiated with neutrons by using JMTR were examined to evaluate the effects of neutron flux and temperature history at the beginning of the irradiation on their mechanical properties. Specimens of SUS304 were irradiated under two different flux conditions up to a dose of 5
10
n/m
. Neutron irradiation of SUS316L specimens up to 210
n/m was performed under the condition of so-called conventional temperature control, which used to be adopted in JMTR. The comparison of 0.2% proof stress obtained from the specimens suggests that the neutron flux and the temperature history does not remarkably influence the mechanical properties of the irradiated stainless steel.
Kitsunai, Yuji*; Kasahara, Shigeki; Chimi, Yasuhiro; Nishiyama, Yutaka; Chatani, Kazuhiro*; Koshiishi, Masato*
no journal, ,
In order to consider mechanism on irradiation-assisted stress corrosion cracking (IASCC), oxide films on surface of locally deformed structure in irradiated stainless steel are investigated. The miniature tensile specimens are made of 316L stainless steels irradiated with neutrons in the Japan Materials Testing Reactor (JMTR). The specimens are strained up to 0.1-2%, and surface structure and crystal misorientation among grains are observed by scanning electron microscope (SEM) and electron backscattering diffraction (EBSD). As a result, visible step structure due to slip plane is appeared on the specimen surface, depending on the neutron fluence and the applied strain level. Furthermore, the data from EBSD suggests that the localization of strain occurred in the vicinity of grain boundaries. The visible step structure characterized from the viewpoints of the morphology and density, and the effects of neutron fluence and stain are discussed on the step structure are discussed.
Yamashita, Shinichiro; Sekio, Yoshihiro; Sakaguchi, Norihito*; Shibayama, Tamaki*; Watanabe, Seiichi*; Tokita, Shun*; Fujii, Hiromichi*; Sato, Yutaka*; Kokawa, Hiroyuki*
no journal, ,
no abstracts in English
Suzudo, Tomoaki; Yamaguchi, Masatake; Hasegawa, Akira*
no journal, ,
Under neutron irradiation Re and Os are produced in W crystals, which are candidate materials for future fusion devices. These impurities are precipitated even under their solid solution limits, i.e. radiation induced precipitation (RIP) occurs. In the present study, we investigated the diffusions of Re and Os in W, which are essential to the development of the RIP. We found that Re and Os formed mixed dumbbells that rotate very easily, and that these dumbbells have 3D motions which are expected to suppress the cavity formation. This may be the explanation of the fact that Re or Os inclusion in W crystals suppress the cavity formation.
alloy under high pressureEndo, Naruki*; Saito, Hiroyuki; Machida, Akihiko
no journal, ,
no abstracts in English
Tsuru, Tomohito; Aoyagi, Yoshiteru*; Kaji, Yoshiyuki; Shimokawa, Tomotsugu*
no journal, ,
In this study, huge-scale atomistic simulations of the polycrystalline thin film containing the Frank-Read source are performed to elucidate the fundamental deformation mechanism of ultrafine-grained metals. While the first plastic deformation occurs by the dislocation bow-out motion within the grain region for both models, the subsequent plastic deformation is strongly influenced by the resistance of the slip transfer by dislocation transmission through grain boundaries. Subsequently, the Bauschinger effect of the ultrafine-grain metals is investigated using three-dimensional polycrystalline model with dislocation sources within the grain region.
Murao, Taisuke*; Sakai, Junichi*; Kido, Osamu*; Yokoyama, Kenichi*; Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi
no journal, ,
no abstracts in English
Nagatomo, Koki*; Yokoyama, Kenichi*; Sakai, Junichi*; Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi
no journal, ,
no abstracts in English
c+a
screw dislocations in MgItakura, Mitsuhiro; Kaburaki, Hideo; Yamaguchi, Masatake; Tsuru, Tomohito
no journal, ,
Fuel cladding in nuclear reactors are made of Zirconium alloy, which has hexagonal crystal structure. Because of the low symmetry of the structure, hexagonal metals are known to have poor ductility and formability, and identification of alloying effect and irradiation effect on the ductility of these metals are currently very important subject. The present study concentrate on the pyramidal dislocations in Mg, which is a typical hexagonal metal suitable for the model studies. The pyramidal dislocations plays a key rolein the ductile deformation and understanding its nature is essential to improve the ductility of the material. The present study revealed for the first time the structure and migration process of the pyramidal dislocations, opening a way to design an alloy of better ductility based on the computational predictions.
Doi, Takashi*; Nishiyama, Yoshitaka*; Teraoka, Yuden; Yoshigoe, Akitaka
no journal, ,
no abstracts in English
Shi, S.*; Ono, Naoko*; Ukai, Shigeharu*; Ishida, Tomonori*; Onuma, Masato*; Abe, Yosuke
no journal, ,
In nano-sized bubble dispersion strengthened copper (BDS-Cu) synthesized by using dissociated gases of poly-methyl methacrylate (PMMA) during spark plasma sintering, the size of nano-bubbles and chemical composition of materials inside nano-bubbles were investigated by means of small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), and transmission electron microscope (TEM). From the neutron scattering intensity difference between BDS-Cu and pure copper, the average radius of nano-bubbles was about 2 nm, which is well agreed with TEM observation. The intensity ratio of X-ray scattering to neutron scattering caused by nano-bubbles suggested the existence of MMA containing hydrogen inside nano-bubbles.