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and CrUOAkiyama, Daisuke*; Kusaka, Ryoji; Kumagai, Yuta; Nakada, Masami; Watanabe, Masayuki; Okamoto, Yoshihiro; Nagai, Takayuki; Sato, Nobuaki*; Kirishima, Akira*
Journal of Nuclear Materials, 568, p.153847_1 - 153847_10, 2022/09
Times Cited Count：3 Percentile：68.71(Materials Science, Multidisciplinary)FeUO, CrUO, and Fe
Cr
UO are monouranates containing pentavalent U. Even though these compounds have similar crystal structures, their formation conditions and thermal stability are significantly different. To determine the factors causing the difference in thermal stability between FeUO and CrUO, their crystal structures were evaluated in detail. A Raman band was observed at 700 cm
in all the samples. This Raman band was derived from the stretching vibration of the O-U-O axis band, indicating that FeCrUO was composed of a uranyl-like structure in its lattice regardless of its "x"' value. M
ssbauer measurements indicated that the Fe in FeUO and FeCrUO were trivalent. Furthermore, FeCrUO lost its symmetry around Fe
with increasing electron densities around Fe, as the abundance of Cr increased. These results suggested no significant structural differences between FeUO and CrUO. Thermogravimetric measurements for UO
, FeUO, and CrUO showed that the temperature at which FeUO decomposed under an oxidizing condition (approximately 800 
C) was significantly lower than the temperature at which the decomposition of CrUO started (approximately 1250 C). Based on these results, we concluded that the decomposition of FeUO was triggered by an "in-crystal" redox reaction, i.e., Fe 
U
Fe
U
, which would not occur in the CrUO lattice because Cr could never be reduced under the investigated condition. Finally, the existence of Cr in FexCrUO effectively suppressed the decomposition of the FeCrUO crystal, even at a very low Cr content.
Suzudo, Tomoaki; Takamizawa, Hisashi; Nishiyama, Yutaka; Caro, A.*; Toyama, Takeshi*; Nagai, Yasuyoshi*
Journal of Nuclear Materials, 540, p.152306_1 - 152306_10, 2020/11
Times Cited Count：9 Percentile：75.92(Materials Science, Multidisciplinary)Spinodal decomposition in thermally aged Fe-Cr alloys leads to significant hardening, which is the direct cause of the so-called 475C-embrittlement. To illustrate how spinodal decomposition induces hardening by atomistic interactions, we conducted a series of numerical simulations as well as reference experiments. The numerical results indicated that the hardness scales linearly with the short-range order (SRO) parameter, while the experimental result reproduced this relationship within statistical error. Both seemingly suggest that neighboring Cr-Cr atomic pairs essentially cause hardening, because SRO is by definition uniquely dependent on the appearance probability of such pairs. A further numerical investigation supported this notion, as it suggests that the dominant cause of hardening is the pinning effect of dislocations passing over such Cr-Cr pairs.
Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro
Materials Transactions, 46(1), p.136 - 139, 2005/01
Times Cited Count：2 Percentile：25.81(Materials Science, Multidisciplinary)The rust layer formed on weathering steel possesses a strong protective ability against corrosives in an atmosphere. This ability is related to the structure of the rust layer. The difference in the protective ability of a rust layer in a Cl-rich environment between conventional weathering steel containing Cr and advanced weathering steel containing Ni is believed to be caused by the differences in local structural and chemical properties between alloying elements, Cr and Ni, in the rust layer. In order to examine the effect of these alloying elements on the structure of the rust layer formed on steel in a Cl-rich environment, we have performed Cr and Ni K-edge X-ray absorption near-edge structure (XANES) measurements for the rust layer of Fe-Cr and Fe-Ni binary alloys exposed to a Cl-rich atmosphere using synchrotron radiation. The results of the Cr K-edge XANES measurements for the rust layer of Fe-Cr binary alloys show that the atomic geometry around Cr depends on the concentration of Cr. Therefore, it is expected that the local structure around Cr in the rust layer is unstable. On the other hand, from the results of the Ni K-edge XANES measurements for the rust layer of Fe-Ni binary alloys, Ni is considered to be positioned at a specific site in the crystal structure of a constituent of the rust layer, such as akagan
ite or magnetite. As a consequence, Ni negligibly interacts with Cl
ions in the rust layer.
Kikuchi, Kenji; Kurata, Yuji; Saito, Shigeru; Futakawa, Masatoshi; Sasa, Toshinobu; Oigawa, Hiroyuki; Wakai, Eiichi; Miura, Kuniaki*
Journal of Nuclear Materials, 318(1-3), p.348 - 354, 2003/05
Times Cited Count：28 Percentile：84.98(Materials Science, Multidisciplinary)Corrosion test of austenitic stainless tube was done under the flowing Pb-Bi condition during 3000 hrs at 450C. Specimen is 316SS produced as a tubing form with 13.8 mm outer diameter, 2 mm thickness and 40 cm length. During the operation, maximum temperature, temperature difference and flow velocity of Pb-Bi at the specimen were kept at 450C, 50C, and 1m/s, respectively. After the test, specimen and components of the loop were cut and examined by optical microscope, SEM, EDX, WDX and X-ray diffraction. Pb-Bi adhered on the surface of the specimen even after Pb-Bi was drained out to the storage tank from the circulating loop. Different results from a stagnant corrosion test were that the specimen surface became rough and the corrosion rate was maximally 0.1mm/3000hrs. And mass transfer from the high temperature to the lower temperature area was observed: crystals of Fe-Cr were found on the tube surface in low-temperature part. The size of crystal was 0.1 
0.2 mm. The depositing crystal was ferrite grain and the chemical composition ratio (mass%) of Fe to Cr was 9:1.
ion irradiationWakai, Eiichi; Hishinuma, Akimichi; Abe, Hiroaki; Takaki, Seiichi*; Abiko, Kenji*
Materials Transactions, JIM, 41(9), p.1176 - 1179, 2000/09
no abstracts in English
Wakai, Eiichi; Hishinuma, Akimichi; Usami, Koji; Kato, Yasushi*; Takaki, Seiichi*; Abiko, Kenji*
Materials Transactions, JIM, 41(9), p.1180 - 1183, 2000/09
no abstracts in English
Takago, S.*; Sasaki, Toshihiko*; Minakawa, Nobuaki; Morii, Yukio; Hirose, Yukio*
Proceedings of 6th International Conference on Residual Stressess (ICRS-6), Vol.1, p.41 - 48, 2000/07
no abstracts in English
; Yamagata, Ichiro; Donomae, Takako; Akasaka, Naoaki
JNC TN9400 2000-046, 24 Pages, 2000/02
lt is well known that solute atoms are segregated on surface, grain boundary, etc. and composition changed partially in irradiated austenitic stainless steel. For understanding radiation induced segregation (RIS), we adopt a Fe-15Cr-20Ni-x (x: Si, Mo) which is basically alloy system in PNC1520, and size of Si, Mo are different from matrix atoms to investigate RIS behaviors. The specimens were irradiated by "Joyo" fast reactor that irradiation condition is 3.5 
10
n/m
(E>0.1Mev) at 476C. After irradiation, the specimen were observed and analyzed with EDS (Energy Dispersive X-ray Spectroscope) of 400kV TEM (Transmission Electron Microscope). The behavior of RIS depends on size of solute atoms of alloy. For example, oversized atoms are decreased and undersized atoms are increased in sink. RIS of voids are as same as or more than grain boundaries and smaller than precipitates. The void denuded zone was existed nearby G.B. in case of combinations between the grains from G.B.0ne of the reasons in this, the voids swepted by moving G.B. in radiation induced G.B. migration.
Wakai, Eiichi; Hishinuma, Akimichi; Miwa, Yukio; Ouchi, Asao*; Isozaki, Seiichi*; Takaki, Seiichi*; Abiko, Kenji*
Materials Transactions, JIM, 41(1), p.136 - 140, 2000/01
no abstracts in English
ion irradiationWakai, Eiichi; Hishinuma, Akimichi; Abe, Hiroaki; Miwa, Yukio; Takaki, Seiichi*; Abiko, Kenji*
Proc of Ultra-High-Purity Metallic-Base Materials (UHPM-98), p.35 - 45, 1998/00
no abstracts in English
Wakai, Eiichi; Hishinuma, Akimichi; Kato, Yasushi*; *; *
Nihon Kinzoku Gakkai Koen Gaiyo, 1994 Shuki (Dai-115-Kai) Taikai, 0, p.488 - 494, 1994/00
no abstracts in English
;
Physical Review Letters, 52(10), p.835 - 838, 1984/00
Times Cited Count：137 Percentile：97.17(Physics, Multidisciplinary)no abstracts in English
;
Physica B; Condensed Matter, 120, p.392 - 396, 1983/00
no abstracts in English
;
Journal of the Physical Society of Japan, 51(2), p.347 - 348, 1982/00
Times Cited Count：13 Percentile：79.53(Physics, Multidisciplinary)no abstracts in English
*; ; ; ; ; Araki, Kunio;
JAERI-M 8574, 28 Pages, 1979/11
no abstracts in English
Suzudo, Tomoaki; Nagai, Yasuyoshi*; Alfredo, C.*
no journal, ,
It is widely known that Fe-Cr binary alloys undergo spinodal decomposition when they are thermally aged, and that this microstructural evolution causes hardening and loss of ductility of the material. The present study is about the first attempt to tackle this problem by exploiting atomistic modeling techniques. We apply Monte Carlo simulation to creating spinodally-decomposed microstructure and molecular dynamics to simulating edge dislocations moving through this microstructure by imposing shearing deformation. We then measure the critical stress as a measure of hardness for many cases over the progress in spinodal decomposition, and succeed in reproducing an experimentally-discovered proportionality between the phase separation parameter and the hardening.
Furukawa, Tomohiro; Takai, Toshihide; Watanabe, Shigeki*; Ishioka, Noriko*
no journal, ,
Authors have started the development of liquid bismuth target system for continuous production of therapeutic radionuclide astatine-211 as an application of liquid metal technology cultivated in above research and development, in recent years. Fe-Cr-Al alloy is one of the candidates of the target window in this system. In order to clarify the corrosion of the target window in pure liquid bismuth, the exposure test at elevated temperature was done for Fe-Cr-Al alloys and their references. The test was conducted under argon gas flow, i.e. saturated dissolved oxygen condition in theory. The temperature and exposure time were 500C and 500 hours, respectively. Results of metallurgical examination after the exposure, it was concluded that the corrosion behavior was basically equivalent to that in lead-bismuth eutectic, which is the candidate coolant of heavy metal cooled fast reactors and accelerator driven systems.
