| 1. |
Hiroyuki Toda, Kyosuke Hirayama, Shogo Yamaguchi, Hiro, Fujihara, Ryota Higa, Kazuyuki Shimizu, Akihisa Takeuchi, Masayuki Uesugi, Dominant Factors Controlling the Initiation of Hydrogen Embrittlement in Al-Zn-Mg Alloy, 10.2320/matertrans.MT-M2023116, 64, 12, 2023.12. |
| 2. |
比嘉 良太, 藤原 比呂, 戸田 裕之, 小林 正和, 海老原 健一, 竹内晃久, Al-Zn-Mg合金における水素脆化発生挙動のマルチモーダル3Dイメージベース解析, 軽金属, 73, 11, 2023.11. |
| 3. |
Growth behavior of pores and hydrogen desorption behavior in pure aluminum and A6061 aluminum alloys. |
| 4. |
Kazuyuki Shimizu, H Toda, Hiro Fujihara, Masatake Yamaguchi, Masayuki Uesugi, Akihisa Takeuchi, Masahiko Nishijima, Yasuhiro Kamada, Hydrogen embrittlement and its prevention in 7XXX aluminum alloys with high Zn concentrations, CORROSION, 10.5006/4300, 79, 8, 818-830, 2023.04, 7xxx aluminum alloys are representative high-strength aluminum alloys; however, mechanical property degradation due to hydrogen hinders further strengthening. We have previously reported that hydrogen embrittlement in 7xxx alloys originates from trapped hydrogen at the MgZn2 precipitate interface, providing high hydrogen trapping energy. 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. Although no significant differences appear between the two alloys regarding the initiation of quasicleavage cracks, the area fractions of final quasicleavage fractures are 16.5% and 1.0% for 0.0%Mn and 0.6%Mn alloys, respectively; this finding indicates that the Mn addition reduces hydrogen-induced fractures. 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. The results of an original hydrogen partitioning analysis show that the dispersion of Mn-based particles (Al12Mn3Si) with high hydrogen trapping abilities reduces the hydrogen concentration at the semicoherent MgZn2 interface and suppresses hydrogen embrittlement. . |
| 5. |
Valary Tubei, Hiroyuki Toda, Worapol Ketanond, Hiro Fujihara, Osamu Takakuwa, Akihisa Takeuchi, Masayuki Uesugi, Direct observation of three-dimensional short fatigue crack closure behavior in Ti-6Al-4V alloy using ultra-high-resolution X-ray microtomography, International Journal of Fatigue, 10.1016/j.ijfatigue.2022.107428, 168, 107428-107428, 2023.03. |
| 6. |
Hiro Fujihara, Kazuyuki Shimizu, Hiroyuki Toda, Akihisa Takeuchi, Masayuki Uesugi, Suppression of Hydrogen Embrittlement due to Local Partitioning of Hydrogen to Dispersed Intermetallic Compound Particles in Al–Zn–Mg–Cu Alloys, MATERIALS TRANSACTIONS, 10.2320/matertrans.mt-l2022007, 63, 10, 1406-1415, 2022.10. |
| 7. |
Ryoichi Oikawa, Kazuyuki Shimizu, Yasuhiro Kamada, Hiroyuki Toda, Hiro Fujihara, Masayuki Uesugi, Akihisa Takeuchi, Influence of Hydrogen on the Damage Behavior of IMC Particles in Al–Zn–Mg–Cu Alloys, MATERIALS TRANSACTIONS, 10.2320/matertrans.mt-l2022020, 63, 12, 1607-1616, 2022.10, In recent years, it has been reported that intermetallic compound particles can suppress hydrogen embrittlement by hydrogen trapping. Some intermetallic particles in aluminum alloys, such as Al7Cu2Fe, have internal hydrogen trap sites; it is proposed that hydrogen embrittlement can be suppressed by preferential hydrogen partitioning in these sites. However, intermetallic compound particles act as fracture origin sites, and excessive addition degrades the mechanical properties of the material. In this study, we quantitatively evaluated the damage and decohesion behavior of intermetallic compound particles in high-hydrogen content 7XXX aluminum alloys by using in situ synchrotron radiation X-ray tomography. The results revealed that the hydrogen particles induced early high-strain localization, and the Al7Cu2Fe particles were damaged in that region due to its brittleness, resulting in early fracture. Hydrogen had no effects on the fracture and debonding behaviors of intermetallic compound particles, suggesting that the observed particle brittle fracture is dependent on their mechanical properties.. |
| 8. |
Yuantao Xu, Hiroyuki Toda, Kazuyuki Shimizu, Yafei Wang, Baptiste Gault, Wei Li, Kyosuke Hirayama, Hiro Fujihara, Xuejun Jin, Akihisa Takeuchi, Masayuki Uesugi, Suppressed hydrogen embrittlement of high-strength Al alloys by Mn-rich intermetallic compound particles, Acta Materialia, 10.1016/j.actamat.2022.118110, 236, 118110-118110, 2022.09, The pursuit of strong and ductile Al alloys with superior resistance to hydrogen embrittlement (HE) is practically significant across the aerospace and transportation industries among others. Unfortunately, effective ways to progress on the strength-HE trade-off for Al-alloys remain elusive. A strategy of suppressing HE by introducing intermetallic compound (IMC) particles to achieve hydrogen redistribution in various trapping sites was proposed. Here, we systematically induce the precipitation of a constant volume fraction of intermetallic compound (IMC) particles by adding one of 14 elements in a ternary Al-Zn-Mg high-strength alloy. We show a strong correlation between hydrogen trapping energies of the IMC obtained from ab initio calculations with the resistance to HE. Mn-rich Al11Mn3Zn2 particles exhibit the highest hydrogen trapping energy (0.859 eV/atom), leading to a decrease by approximately 5 orders of magnitude in the hydrogen occupancy in eta(2) (MgZn2) phase interfaces and grain boundaries, where HE cracks initiate. The Mn-addition did not deteriorate the ductility and most Al11Mn3Zn2 particles remained intact during plastic deformation which was revealed by in-situ 3D X-ray tomography. Hydrogen-induced strain localization at eta(2) phase interfaces and grain boundaries were inhibited due to strong hydrogen trapping capacity of Al11Mn3Zn2, hence preventing HE cracks initiation. Our approach effectively suppresses hydrogen-induced cracks without sacrificing the ductility, and our strategy can help the design roadmap of HE-tolerant high-strength metallic alloys. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.. |
| 9. |
Influence of hydrogen on the damage behavior of IMC particles in Al-Zn-Mg-Cu alloys. |
| 10. |
Yafei Wang, Hiroyuki Toda, Yuantao Xu, Kazuyuki Shimizu, Kyosuke Hirayama, Hiro Fujihara, Akihisa Takeuchi, Masayuki Uesugi, In-situ 3D observation of hydrogen-assisted particle damage behavior in 7075 Al alloy by synchrotron X-ray tomography, Acta Materialia, 10.1016/j.actamat.2022.117658, 227, 117658-117658, 2022.04. |
| 11. |
Fujihara, Hiro, Toda, Hiroyuki, Arita, Makoto, Shimizu, Kazuyuki, Takeuchi, Akihisa, Uesugi, Kentaro, Assessment of Hydrogen Accumulation Behavior in Al-Zn-Mg Alloy under Strain with Kelvin Force Microscopy, MATERIALS TRANSACTIONS, 10.2320/matertrans.L-M2020873, 62, 5, 636-641, 2021.05. |
| 12. |
Analysis of Hydrogen Content in Pure Palladium via Neutron Radiography and Tomography
Hydrogen in materials degrades mechanical properties, which is widely recognized as hydrogen embrittlement. To understand hydrogen embrittlement, it is necessary to clarify the accumulation behavior of hydrogen under stress. The neutron radiography and neutron tomography techniques are applied to examine whether hydrogen accumulation behavior can be visualized directly. Palladium specimens with and without hydrogen were prepared for the neutron imaging experiment under stress. Solute hydrogen has caused distinct contrast change in both the neutron radiography and neutron tomography. Hydrogen distribution at a notch-tip in a loaded specimen has not been visualized in the tomographic cross-sectional images. It can be inferred that this is fundamentally attributable to low spatial resolution of the present imaging set-up, and possibility to visualize hydrogen distribution due to loading is discussed.. |
| 13. |
Shimizu, Kazuyuki, Toda, Hiroyuki, Kadogawa, Chihiro, Fujihara, Hiro, Takeuchi, Akihisa, Influence of nanovoids in the hydrogen embrittlement fracture of Al-Zn-Mg-Cu alloys, Materialia, 10.1016/j.mtla.2020.100667, 11, 2020.06. |
| 14. |
Shimizu, Kazuyuki, Toda, Hiroyuki, Fujihara, Hiro, Hirayama, Kyosuke, Uesugi, Kentaro, Takeuchi, Akihisa, Hydrogen partitioning behavior and related hydrogen embrittlement in Al-Zn-Mg alloys, ENGINEERING FRACTURE MECHANICS, 10.1016/j.engfracmech.2019.106503, 216, 2019.07. |
| 15. |
Fujihara, Hiro, Toda, Hiroyuki, Shimizu, Kazuyuki, Takeuchi, Akihisa, Uesugi, Kentaro, Assessment of hydrogen accumulation behavior in stressed Al-Zn-Mg aluminum alloys by means of Kelvin force microscopy, The 16th International Conference on Aluminum Alloys (ICAA16), 2018.06. |
| 16. |
Fujihara, Hiro; Toda, Hiroyuki; Shimizu, Kazuyuki; Takeuchi, Akihisa; Uesugi, Kentaro, Hydrogen trapping behavior in Al-Zn-Mg alloys, The 9th Pacific Rim International Conference on Advanced Materials and Processing (PRICM9), 2016.08. |
