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Higa, Ryota*; Fujihara, Hiro*; Toda, Hiroyuki*; Kobayashi, Masakazu*; Ebihara, Kenichi; Takeuchi, Akihisa*
Keikinzoku, 73(11), p.530 - 536, 2023/11
In Al-Zn-Mg alloys, suppression of hydrogen embrittlement is necessary to improve their strength. In this study, the distribution of stress, strain, and hydrogen concentration in the actual fracture region was investigated using the crystal plasticity finite element method and hydrogen diffusion analysis based on a model derived from three-dimensional polycrystalline microstructural data obtained by X-ray CT. In addition, the distributions of stress, strain, and hydrogen concentration were compared with the actual crack initiation behavior by combining in-situ observation of tensile tests using X-ray CT and simulation. The results show that stress loading perpendicular to the grain boundary due to crystal plasticity dominates grain boundary crack initiation. It was also found that internal hydrogen accumulation due to crystal plasticity has little effect on crack initiation.
Mitsui, Seiichiro
Kinzoku, 93(3), p.211 - 218, 2023/03
As part of research and development of geological disposal, "natural analogues" have been applied to validate concept of models and evaluation methodologies for performance assessment. By introducing our research results on natural analogues, this paper presents how we have utilized knowledge of excavated archaeological artifacts for geological disposal studies.
Kurihara, Kensuke*; Lobzenko, I.; Tsuru, Tomohito; Serizawa, Ai*
Keikinzoku, 72(7), p.427 - 429, 2022/07
Nanoclusters formed of the Al-Mg-Si alloy affect the aging behavior of the alloy depending on the formation temperature. Since Al, Mg and Si have adjacent atomic numbers, it is difficult to analyze them using the X-ray diffraction method. Therefore, in recent years, Al-Mg-Ge alloys in which Si is replaced with the homologous element Ge have been used. Attempts have been made to analyze the structure of the precipitate. In this study, we quantitatively evaluate the interaction between solute atoms and pores in Al-Mg-Si alloys and Al-Mg-Ge alloys using first-principles calculations based on the density general function theory, and solute atoms. From the viewpoint of bond stability between pores and pores, the precipitation behavior of both alloys was compared and examined.
Kurihara, Kensuke*; Lobzenko, I.; Tsuru, Tomohito; Serizawa, Ai*
Keikinzoku, 72(2), p.47 - 53, 2022/02
Nanoclusters formed in Al-Mg-Si alloys affect the aging behavior of the alloys depending on the formation temperature. In the present study, first-principles calculations were carried out to evaluate the two- and three-body interactions between Mg, Si atoms and vacancies in the Al matrix and to estimate the effect of local bond structures on the formation of nanoclusters. Monte Carlo simulations were subsequently performed to investigate the stable structure of nanocluster formed in Al-Mg-Si alloy. We found that Mg-Si bond and Si-Vac bond were stable in Al matrix. The result showed that the solute atoms are easy to aggregate with another type of atoms and that Si atom had a strong attractive interaction with a vacancy. Mg-Si-vacancy three-body bond were more stable than Mg-Si two-body bond and Si-vacancy two-body bond in Al matrix. Therefore, vacancies were strongly trapped within the cluster region due to the stable local bonds composed of Mg and Si atoms which indicates that the nanoclusters in Al matrix were thermally stabilized by the stable bonds between solute atoms and vacancy. In addition, these results suggested that inner bonds of nanocluster played a significant role in not only the thermal stability but also the formation and growth behavior of nanoclusters during aging at low temperatures.
Harjo, S.
Kinzoku, 91(3), p.221 - 227, 2021/03
no abstracts in English
Saito, Junichi; Kobayashi, Yohei*; Shibutani, Hideo*
Nihon Kinzoku Gakkai-Shi, 85(3), p.110 - 119, 2021/03
Times Cited Count：1 Percentile：7.67(Metallurgy & Metallurgical Engineering)Tsuru, Tomohito
Keikinzoku, 70(2), p.73 - 81, 2020/02
Elements strategy becomes important to investigate alternative materials of rare metals. I have dedicated to establish a new approach based on computational methods. In the present paper, I propose two approaches based on first-principles and theory of dislocations. These methods are introduced to magnesium alloys.
Shimizu, Kazuyuki*; Hayashida, Hirotoshi*; Toda, Hiroyuki*; Kai, Tetsuya; Matsumoto, Yoshihiro*; Matsumoto, Yoshihisa*
Nihon Kinzoku Gakkai-Shi, 83(11), p.434 - 440, 2019/11
Times Cited Count：1 Percentile：6.1(Metallurgy & Metallurgical Engineering)Hanari, Toshihide; Kawabata, Kuniaki
Kinzoku, 89(7), p.582 - 588, 2019/07
no abstracts in English
Ogawa, Wataru*; Shobu, Takahisa; Kakehi, Mizue*; Kuratani, Fumiyasu*; Koide, Toshio*; Monju, Yoshiyuki*; Mizuta, Taiji*
Nihon Kinzoku Gakkai-Shi, 83(4), p.128 - 135, 2019/04
Times Cited Count：2 Percentile：6.1(Metallurgy & Metallurgical Engineering)Cymbals are percussion musical instruments with a simpler structure than other musical instruments. Therefore, their material composition basically decides the sound quality and decay time rather than the skill of the player. In this study, specimens of cymbals to which Titanium, Zirconium and Iron were added were prepared. From the difference of diffraction rings by synchrotron radiation X-rays, the crystal structure of the specimens of cymbals prepared by various manufacturing processes was analyzed in order to investigate the relationship between the crystal structure associated with the material and manufacturing process used and the damping of the sound of cymbals. As a result, it was found that the changes in the crystal structure were due to the manufacturing process used. In addition, it was clarified that the changes affected the damping of the sound of cymbals.
Yamaguchi, Masatake; Tsuru, Tomohito; Ebihara, Kenichi; Itakura, Mitsuhiro
Keikinzoku, 68(11), p.588 - 595, 2018/11
no abstracts in English
Ebihara, Kenichi; Yamaguchi, Masatake; Tsuru, Tomohito; Itakura, Mitsuhiro
Keikinzoku, 68(11), p.596 - 602, 2018/11
Hydrogen embrittlement (HE) is considered as one cause of stress corrosion cracking. HE is a serious problem in the development of high strength aluminum alloy as with steels. For understanding HE, it is inevitable to know hydrogen trapping states in the alloys and it can be identified using thermal desorption spectrometry of H. In this study, we numerically simulated thermal desorption spectra of hydrogen in aluminum for a cylindrical and a plate specimens and interpreted the desorption peaks included in them on the basis of the trap site concentration and the trap energy. As a result, we found that the peak at the lowest-temperature side can result from grain boundaries and confirmed that the reported interpretation for other peaks is reasonable. We also obtained the result showing the possibility that the trap site concentration of defects changes during heating the specimens. This result may give a suggestion for the interpretation of temperature desorption spectra of steels.
Kokubo, Hiroki*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Yamano, Hidemasa
Nihon Kinzoku Gakkai-Shi, 82(10), p.400 - 402, 2018/09
Times Cited Count：7 Percentile：36.32(Metallurgy & Metallurgical Engineering)It is important to obtain the viscosity of a mixed alloy consisting of molten stainless steel and boron-carbide (SUS316L + B
C alloy) for the improvement of severe accident assessment methodology for sodium-cooled fast reactors. In this study, the viscosities of the molten nickel (Ni) and stainless steel (SUS316L) were measured by the oscillating crucible method to confirm the performance of the viscosity measurement apparatus as a first step. The viscosities of molten Ni and SUS316L melts were measured up to 1823 K. It was found that the measured viscosity values of molten Ni and SUS316L were estimated from the deviation of the experimental data, were 
4% and 3%, respectively. It was also found that those of molten Ni and SUS316L were close to those of the literature values of molten Ni and similar composite stainless steels. Moreover, we tentatively measured the viscosity of molten SUS316L-5 mass%BC alloy. The fitted results of the viscosity for molten Ni and SUS316L were obtained.
Narita, Hirokazu*; Suzuki, Tomoya*; Motokawa, Ryuhei
Nihon Kinzoku Gakkai-Shi, 81(4), p.157 - 167, 2017/04
Times Cited Count：17 Percentile：62.47(Metallurgy & Metallurgical Engineering)Tsuchiya, Kunihiko; Nagao, Yoshiharu
Kinzoku, 86(10), p.893 - 899, 2016/10
no abstracts in English
Sato, Shigeo*; Onuki, Yusuke*; Shobu, Takahisa; Shiro, Ayumi*; Tashiro, Hitoshi*; Todoroki, Hidekazu*; Suzuki, Shigeru*
Kinzoku, 86(8), p.654 - 660, 2016/08
no abstracts in English
Kawamura, Hiroshi; Yamada, Tomonori
Kinzoku, 86(7), p.580 - 589, 2016/07
no abstracts in English
Kaito, Takeji
Shinayaka De Tsuyoi Tekko Zairyo; Kakushinteki Kozoyo Kinzoku Zairyo No Kaihatsu Saizensen, p.393 - 399, 2016/06
no abstracts in English
Sn
by time resolved X-ray diffractionMachida, Akihiko; Higuchi, Kensuke*; Katayama, Yoshinori; Sakaki, Koji*; Kim, H.*; Nakamura, Yumiko*
Nihon Kinzoku Gakkai-Shi, 79(3), p.124 - 130, 2015/03
Times Cited Count：4 Percentile：22.66(Metallurgy & Metallurgical Engineering)Structural changes on hydrogen absorption process of hydrogen absorbing alloy LaNiSn have been investigated by time-resolved X-ray diffraction measurements using synchrotron radiation source. We have found the transient intermediate phase between the solid solution and hydride phases of LaNiSn under non-equilibrium hydrogen pressure condition at room temperature. LaNiSn has transformed into the hydride through three phase co-existing state. The hydrogen content of the intermediate phase estimated from the unit cell volume is independent of the induced hydrogen gas pressure. The variation of lattice constants indicate that the hydrogen atoms are located at the La
Ni(Ni,Sn) octahedron and La(Ni,Sn) tetrahedron in the intermediate phase.
(Fe
Mn
)
(
, 
)Sakaki, Koji*; Kim, H.*; Machida, Akihiko; Watanuki, Tetsu; Nakamura, Yumiko*
Nihon Kinzoku Gakkai-Shi, 79(3), p.112 - 117, 2015/03
Times Cited Count：3 Percentile：17.8(Metallurgy & Metallurgical Engineering)no abstracts in English
