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Journal Articles

Hydrogen embrittlement and its prevention in 7XXX aluminum alloys with high Zn concentrations

Shimizu, Kazuyuki*; Toda, Hiroyuki*; Fujihara, Hiro*; Yamaguchi, Masatake; Uesugi, Masayuki*; Takeuchi, Akihisa*; Nishijima, Masahiko*; Kamada, Yasuhiro*

Corrosion, 79(8), p.818 - 830, 2023/08

7xxx aluminum alloys are representative high-strength aluminum alloys; however, mechanical property degradation due to hydrogen hinders further strengthening. We propose the dispersion of Mn-based second-phase particles as a novel technique for preventing 7xxx aluminum alloy hydrogen embrittlement. In this study, the deformation and fracture behaviors of high hydrogen 7xxx alloys containing 0.0% Mn and 0.6% Mn are observed in situ using synchrotron radiation X-ray tomography. The obtained macroscopic hydrogen embrittlement is quantitatively analyzed based on hydrogen partitioning in alloys. Adding 0.6% Mn, generating second-phase particles with high hydrogen trapping abilities, significantly suppresses hydrogen-induced quasicleavage fracture.

Journal Articles

Identification of hydrogen trapping in aluminum alloys $$via$$ muon spin relaxation method and first-principles calculations

Tsuru, Tomohito; Nishimura, Katsuhiko*; Matsuda, Kenji*; Nunomura, Norio*; Namiki, Takahiro*; Lee, S.*; Higemoto, Wataru; Matsuzaki, Teiichiro*; Yamaguchi, Masatake; Ebihara, Kenichi; et al.

Metallurgical and Materials Transactions A, 54(6), p.2374 - 2383, 2023/06

Although hydrogen embrittlement susceptibility of high-strength Al alloys is recognized as a critical issue in the practical use of Al alloys, identifying the hydrogen trapping or distribution has been challenging. In the present study, an effective approach based on experiment and simulation is proposed to explore the potential trap sites in Al alloys. Zero-field muon spin relaxation experiments were carried out for Al-0.5%Mg, Al-0.2%Cu, Al-0.15%Ti, Al-0.011%Ti, Al-0.28%V, and Al-0.015%V (at.%) in the temperature range from 5 to 300 K. The temperature variations of the dipole field widths have revealed three peaks for Al-0.5%Mg, four peaks for Al-0.2%Cu, three peaks for Al-0.011%Ti and Al-0.015%V. Atomic configurations of the muon trapping sites corresponding to the observed $$Delta$$ peaks are well assigned using the first-principles calculations for the trap energies of hydrogen around a solute and solute-vacancy pair. The extracted linear relationship between the muon $$Delta$$ peak temperature and the trap energy enables us to explore the potential alloying elements and their complex that have strong binding energies with hydrogen in Al alloys.

Journal Articles

Reports of electro-polishing implementation for quarter-wave resonators, 2

Nii, Keisuke*; Ida, Yoshiaki*; Ueda, Hideki*; Yamaguchi, Takanori*; Kabumoto, Hiroshi; Kamiya, Junichiro; Kondo, Yasuhiro; Tamura, Jun; Harada, Hiroyuki; Matsui, Yutaka; et al.

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.601 - 604, 2023/01

no abstracts in English

Journal Articles

Kinetics of the interfacial curing reaction for an epoxy-amine mixture

Yamaguchi, Ko*; Kawaguchi, Daisuke*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Yamamoto, Satoru*; Tanaka, Keiji*

Physical Chemistry Chemical Physics, 24(36), p.21578 - 21582, 2022/09

Journal Articles

Reports of electropolishing implementation for quarter-wave resonators

Nii, Keisuke*; Ida, Yoshiaki*; Ueda, Hideki*; Yamaguchi, Takanori*; Kabumoto, Hiroshi; Kamiya, Junichiro; Kondo, Yasuhiro; Tamura, Jun; Harada, Hiroyuki; Matsui, Yutaka; et al.

Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.334 - 337, 2021/10

no abstracts in English

Journal Articles

Masses of exotic nuclei

Yamaguchi, Takayuki*; Koura, Hiroyuki; Litvinov, Yu. A.*; Wang, M.*

Progress in Particle and Nuclear Physics, 120, p.103882_1 - 103882_98, 2021/09

 Times Cited Count:20 Percentile:79.38(Physics, Nuclear)

Journal Articles

Spontaneous debonding behaviour of reinforcement fine particles in aluminium; Toward high-strength metallic materials development

Toda, Hiroyuki*; Tsuru, Tomohito; Yamaguchi, Masatake; Matsuda, Kenji*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*

Kagaku, 75(10), p.48 - 53, 2020/10

Highly-concentrated precipitations play therefore dominant role in mechanical properties and hydrogen embrittlement of aluminum alloys. It has been considered that the coherent interface between matrix and precipitation does not contribute to the crack initiation and embrittlement due to its coherency. Here, we discovered the origin of unprecedented quasi-cleavage fracture mode. Hydrogen partitioning at various defect sites is investigated comprehensively combined with experiment, theory and first-principles calculations. We demonstrate that despite low excess free volume, the aluminum-precipitation interface is more preferable trap site than void and grain boundary. The cohesivity of the interface deteriorates significantly with increasing occupancy while hydrogen atoms are trapped stably up to extremely high occupancy equivalent to spontaneous cleavage.

Journal Articles

Hydrogen trapping in Mg$$_2$$Si and Al$$_7$$FeCu$$_2$$ intermetallic compounds in aluminum alloy; First-principles calculations

Yamaguchi, Masatake; Tsuru, Tomohito; Ebihara, Kenichi; Itakura, Mitsuhiro; Matsuda, Kenji*; Shimizu, Kazuyuki*; Toda, Hiroyuki*

Materials Transactions, 61(10), p.1907 - 1911, 2020/10

 Times Cited Count:7 Percentile:56.69(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Non-invasive imaging of radiocesium dynamics in a living animal using a positron-emitting $$^{127}$$Cs tracer

Suzui, Nobuo*; Shibata, Takuya; Yin, Y.-G.*; Funaki, Yoshihito*; Kurita, Keisuke; Hoshina, Hiroyuki*; Yamaguchi, Mitsutaka*; Fujimaki, Shu*; Seko, Noriaki*; Watabe, Hiroshi*; et al.

Scientific Reports (Internet), 10, p.16155_1 - 16155_9, 2020/10

 Times Cited Count:2 Percentile:24.76(Multidisciplinary Sciences)

Journal Articles

The Possible transition mechanism for the meta-stable phase in the 7xxx aluminium

Bendo, A.*; Matsuda, Kenji*; Nishimura, Katsuhiko*; Nunomura, Norio*; Tsuchiya, Taiki*; Lee, S.*; Marioara, C. D.*; Tsuru, Tomohito; Yamaguchi, Masatake; Shimizu, Kazuyuki*; et al.

Materials Science and Technology, 36(15), p.1621 - 1627, 2020/09

 Times Cited Count:5 Percentile:47.92(Materials Science, Multidisciplinary)

Metastable phases in aluminum alloys are the primary nano-scale precipitates which have the biggest contribution to the increase in the tangible mechanical properties. The continuous increase in hardness in the 7xxx aluminum alloys is associated with the phase transformation from clusters or GP-zones to the metastable $$eta'$$ phase. The transformation which is structural and compositional should occur following the path of the lowest activation energy. This work is an attempt to gain insight into how the structural transformation may occur based on the shortest route of diffusion for the eventual structure to result in that of $$eta'$$ phase. However, for the compositional transformation to occur, the proposed mechanism may not stand, since it is a prerequisite for the atoms to be at very precise positions in the aluminum lattice, at the very beginning of structural transformation, which may completely differ from that of the GP-zones atomic arrangements.

Journal Articles

Hydrogen-accelerated spontaneous microcracking in high-strength aluminium alloys

Tsuru, Tomohito; Shimizu, Kazuyuki*; Yamaguchi, Masatake; Itakura, Mitsuhiro; Ebihara, Kenichi; Bendo, A.*; Matsuda, Kenji*; Toda, Hiroyuki*

Scientific Reports (Internet), 10, p.1998_1 - 1998_8, 2020/04

 Times Cited Count:21 Percentile:83.04(Multidisciplinary Sciences)

Age-hardening has been one and only process to achieve high strength aluminum alloys since unlike iron and titanium, pure aluminum does not have other solid phases during heat treatment. Highly-concentrated precipitations play therefore dominant role in mechanical properties and hydrogen embrittlement of aluminium alloys. It has been considered that the coherent interface between matrix and precipitation does not contribute to the crack initiation and embrittlement due to its coherency. Here, we discovered the origin of unprecedented quasi-cleavage fracture mode. Hydrogen partitioning at various defect sites is investigated comprehensively combined with experiment, theory and first-principles calculations. We demonstrate that despite low excess free volume, the aluminum-precipitation interface is more preferable trap site than void and grain boundary. The cohesivity of the interface deteriorates significantly with increasing occupancy while hydrogen atoms are trapped stably up to extremely high occupancy equivalent to spontaneous cleavage.

Journal Articles

An Unreported precipitate orientation relationship in Al-Zn-Mg based alloys

Bendo, A.*; Matsuda, Kenji*; Lervik, A.*; Tsuru, Tomohito; Nishimura, Katsuhiko*; Nunomura, Norio*; Holmestad, R.*; Marioara, C. D.*; Shimizu, Kazuyuki*; Toda, Hiroyuki*; et al.

Materials Characterization, 158, p.109958_1 - 109958_7, 2019/12

 Times Cited Count:15 Percentile:78.81(Materials Science, Multidisciplinary)

Characterization of precipitates in Al-Zn-Mg alloys, using a combination of electron diffraction, bright field transmission electron microscopy and atomic scale scanning transmission electron microscopy imaging revealed the presence of an unreported $$eta$$$$_{13}$$ orientation relationship between the $$eta$$-MgZn$$_2$$ phase and the Al lattice with the following orientation relationship (0001)$$eta$$ $$||$$ (120)$$_{rm Al}$$ and ($$2bar{1}bar{1}0$$)$$eta$$ $$||$$ (001)$$_{rm Al}$$, plate on (120)$$_{rm Al}$$. The precipitate interfaces were observed and analyzed along two projections 90$$^{circ}$$ to one-another. The precipitate coarsening was through the common thickening ledge mechanism. The ledges were significantly stepped along one lateral direction. An interface relaxation model using density functional theory was carried out to explain the precipitate behavior.

Journal Articles

Effect of copper addition on precipitation behavior near grain boundary in Al-Zn-Mg alloy

Matsuda, Kenji*; Yasumoto, Toru*; Bendo, A.*; Tsuchiya, Taiki*; Lee, S.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Marioara, C. D.*; Lervik, A.*; Holmestad, R.*; et al.

Materials Transactions, 60(8), p.1688 - 1696, 2019/08

 Times Cited Count:13 Percentile:63.77(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Characterisation of structural similarities of precipitates in Mg-Zn and Al-Zn-Mg alloys systems

Bendo, A.*; Maeda, Tomoyoshi*; Matsuda, Kenji*; Lervik, A.*; Holmestad, R.*; Marioara, C. D.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Toda, Hiroyuki*; Yamaguchi, Masatake; et al.

Philosophical Magazine, 99(21), p.2619 - 2635, 2019/07

 Times Cited Count:26 Percentile:83.26(Materials Science, Multidisciplinary)

Journal Articles

Abnormally enhanced diamagnetism in Al-Zn-Mg alloys

Nishimura, Katsuhiko*; Matsuda, Kenji*; Lee, S.*; Nunomura, Norio*; Shimano, Tomoki*; Bendo, A.*; Watanabe, Katsumi*; Tsuchiya, Taiki*; Namiki, Takahiro*; Toda, Hiroyuki*; et al.

Journal of Alloys and Compounds, 774, p.405 - 409, 2019/02

 Times Cited Count:3 Percentile:18.28(Chemistry, Physical)

Journal Articles

Optimization of mechanical properties in aluminum alloys $$via$$ hydrogen partitioning control

Toda, Hiroyuki*; Yamaguchi, Masatake; Matsuda, Kenji*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Su, H.*; Fujihara, Hiro*; Ebihara, Kenichi; Itakura, Mitsuhiro; Tsuru, Tomohito; et al.

Tetsu To Hagane, 105(2), p.240 - 253, 2019/02

 Times Cited Count:0 Percentile:0(Metallurgy & Metallurgical Engineering)

no abstracts in English

Journal Articles

First-principles calculation of multiple hydrogen segregation along aluminum grain boundaries

Yamaguchi, Masatake; Ebihara, Kenichi; Itakura, Mitsuhiro; Tsuru, Tomohito; Matsuda, Kenji*; Toda, Hiroyuki*

Computational Materials Science, 156, p.368 - 375, 2019/01

 Times Cited Count:23 Percentile:77.63(Materials Science, Multidisciplinary)

The segregation of multiple hydrogen atoms along aluminum (Al) grain boundaries (GBs) and fracture surfaces (FSs) was investigated through first-principles calculations considering the characteristics of GBs. The results indicate that hydrogen segregation is difficult along low-energy GBs. The segregation energy of multiple hydrogen atoms along GBs and FSs and the cohesive energy was obtained for three types of high-energy Al GBs. With increasing hydrogen segregation along the GBs, the cohesive energy of the GB decreases and approaches zero with no decrease in GB segregation energy. The GB cohesive energy decreases in parallel with the volume expansion of the region of low electron density along the GB.

Journal Articles

Microstructure evolution in a hydrogen charged and aged Al-Zn-Mg alloy

Bendo, A.*; Matsuda, Kenji*; Lee, S.*; Nishimura, Katsuhiko*; Toda, Hiroyuki*; Shimizu, Kazuyuki*; Tsuru, Tomohito; Yamaguchi, Masatake

Materialia, 3, p.50 - 56, 2018/11

Journal Articles

Development of semi-implicit particle method for simulating sodium-water chemical reaction

Li, J.*; Jang, S.*; Yamaguchi, Akira*; Uchibori, Akihiro; Takata, Takashi; Ohshima, Hiroyuki

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 4 Pages, 2018/11

The sodium-water reaction model is developed in particle methods. Two chemical reaction model, called surface reaction model and gas-phase reaction model are developed in the particle method. Validation on the case of vapor injection into liquid water is conducted and good consistency of jet velocity evolution along jet trajectory is obtained. Finally, sodium-water chemical reaction in a configuration of multiple tube bundles is simulated. Jet velocity, water vapor fraction and temperature are investigated and reasonable results are observed, which presents promising future of this methodology.

Journal Articles

First-principles study of hydrogen segregation at the MgZn$$_{2}$$ precipitate in Al-Mg-Zn alloys

Tsuru, Tomohito; Yamaguchi, Masatake; Ebihara, Kenichi; Itakura, Mitsuhiro; Shiihara, Yoshinori*; Matsuda, Kenji*; Toda, Hiroyuki*

Computational Materials Science, 148, p.301 - 306, 2018/06

 Times Cited Count:37 Percentile:82.38(Materials Science, Multidisciplinary)

Hydrogen embrittlement susceptibility of high strength 7xxx series Al alloys has been recognized as the critical issues in the practical use of Al alloys. Focusing on the interface between MgZn$$_{2}$$ precipitates and an Al matrix, which is considered as one of the important segregation sites in these alloys, we investigated the stable $$eta$$-MgZn$$_{2}$$-Al interface, and the possible hydrogen trap sites in MgZn$$_{2}$$ and at the $$eta$$-MgZn$$_{2}$$-Al interface via first-principles calculation. Most of the interstitial sites inside the MgZn$$_{2}$$ crystal were not possible trap sites because their energy is relatively higher than that of other trap sites. The trap energy of the most favorable site at the $$eta$$-MgZn$$_{2}$$-Al is approximately -0.3 eV/H, which is more stable that of the interstitial site at the grain boundary. The interface between MgZn$$_{2}$$ and Al is likely to be a possible trap site in Al alloys.

298 (Records 1-20 displayed on this page)