Reconsideration of numerical model for hydrogen thermal desorption spectra of iron with hydrogen-enhanced strain-induced vacancies

Ebihara, Kenichi; Yamaguchi, Masatake; Itakura, Mitsuhiro

Metallurgical and Materials Transactions A, 57(4), p.1480 - 1489, 2026/04

https://doi.org/10.1007/s11661-026-08146-7

Hydrogen (H) embrittlement is an important issue for steel. The experimental thermal desorption spectra of H from an iron sample containing H-enhanced strain-induced vacancies (Vs) were successfully reproduced by revising a previous numerical model. In the revised model, we adopted concentration variables for Vs and V clusters, which are distinguished by the number of trapped H atoms. This revision eliminated the assumption of V and V cluster migration, required in the original model. Simulation results of the revised model revealed that the spike-like desorption on the peak attributed to Vs and V clusters in the spectra simulated by the original model was an artifact caused by the assumption. In addition, it was suggested that V clusters can exist other than Vs in the specimens after deformation with H charging. It is considered that the revised model is a useful framework for studying Vs and V clusters under H-affected conditions.

Revisiting hydrogen trapping in Mg(Al, Zn) Approximant crystal; Influence of chemical disorder

Shimizu, Kazuyuki*; Yamaguchi, Masatake; Akamaru, Satoshi*; Nishimura, Katsuhiko*; Abe, Rion*; Sasaki, Taisuke*; Wang, Y.*; Toda, Hiroyuki*

Scripta Materialia, 265, p.116730_1 - 116730_7, 2025/08

https://doi.org/10.1016/j.scriptamat.2025.116730

Hydrogen embrittlement in Al-Zn-Mg alloys; Semispontaneous decohesion of precipitates

Shimizu, Kazuyuki*; Toda, Hiroyuki*; Hirayama, Kyosuke*; Fujihara, Hiro*; Tsuru, Tomohito; Yamaguchi, Masatake; Sasaki, Taisuke*; Uesugi, Masayuki*; Takeuchi, Akihisa*

International Journal of Hydrogen Energy, 109, p.1421 - 1436, 2025/03

https://doi.org/10.1016/j.ijhydene.2025.02.123

Our preceding investigation revealed that multiple hydrogen traps at coherent interfaces of MgZn precipitates initiated spontaneous interface decohesion, causing hydrogen-induced quasicleavage cracking in Al-Zn-Mg alloys. Herein, we performed a quantitative and systematic investigation to discern the mechanisms by which hydrogen trapped at coherent/semi-coherent interfaces of precipitates could influence macroscopic hydrogen embrittlement by modulating the coherent interface of MgZn through aging. To explore this hydrogen embrittlement phenomenon based on hydrogen trapping at the precipitate interface, we determined the hydrogen trapping energy of the semi-coherent MgZn interface via first-principles calculations (0.56 eV/atom). Hydrogen partitioning of all hydrogen trapping sites, including vacancies, grain boundaries, and coherent and semi-coherent MgZn interfaces, revealed that in overaged alloys, over 90% of the hydrogen was sequestered at semi-coherent interfaces. Owing to the inherent characteristics of the MgZn interface, the hydrogen sequestered at the semi-coherent interface decreased the interfacial cohesive energy, causing semispontaneous decohesion of the interface and quasicleavage fracture in the Al-Zn-Mg alloys. These results implied that intergranular fracture was not directly induced by hydrogen trapped at grain boundaries but rather by the decohesion of precipitate interfaces along grain boundaries.

Quantitative estimation method of the effect of segregated solute on hydrogen-enhanced decohesion at a grain boundary

Yamaguchi, Masatake; Ebihara, Kenichi; Itakura, Mitsuhiro; Tsuru, Tomohito

Scripta Materialia, 255, p.116366_1 - 116366_5, 2025/01

https://doi.org/10.1016/j.scriptamat.2024.116366

Reduction of grain boundary cohesive energy by hydrogen has been considered as one of the candidate causes of grain boundary fracture in steels and aluminum alloys. Recently, the effects of grain boundary segregation elements have been investigated by first-principles calculations, but there are few studies that quantitatively estimate the grain boundary cohesive energy. In this study, we describe a quantitative evaluation method using first-principles calculation results and show some examples of experimental calculations.

Effects of antagonistic interaction between Cr and Ni on hydrogen solubility in a Fe-Cr-Ni ternary austenitic system; A First-principles calculation

Moriyama, Junichiro*; Yamaguchi, Masatake; Takakuwa, Osamu*

Materials Today Communications (Internet), 40, p.110059_1 - 110059_9, 2024/08

https://doi.org/10.1016/j.mtcomm.2024.110059

The present study systematically investigates hydrogen (H) solubility within multi-component alloying (Cr, Ni) interaction in Fe-Cr-Ni-based austenitic alloys, which generates a novel H-induced improvement in the strength-ductility balance that is a function of dissolved H-content. We analyzed, using first-principles calculations, H-absorption energy that is directly linked to H-solubility, in an Fe-Cr-Ni face-centered cubic (FCC) ternary system with various configurations of Cr and Ni atoms. The results we obtained clarified the effects of antagonistic interactions between Cr and Ni atoms on H-absorption energy even though both alloying elements independently reduce H-absorption energy at adjacent octahedral sites (O-sites). The present study makes it possible to comprehensively predict the H-solubility of various Fe-Cr-Ni austenitic alloys by taking account of the antagonistic Cr-Ni interaction.

Crystal defects and first-principles calculations; Grain boundary embrittlement, slip deformation, etc.

Yamaguchi, Masatake

Nihon Genshiryoku Gakkai-Shi ATOMO, 66(6), p.291 - 294, 2024/06

https://doi.org/10.3327/jaesjb.66.6_291

First-principles calculations of lattice defects in metals became available around year 2000 and were gradually performed for planar defects such as surface and grain boundaries, point defects such as atomic vacancies, and line defects such as dislocation cores, in the order of ease of calculation. The author introduces some examples of first-principles calculations of microscopic properties, which seem to strongly influence macroscopic material properties.

First-principles calculations of hydrogen trapping energy on incoherent interfaces of aluminum alloys

Yamaguchi, Masatake; Ebihara, Kenichi; Tsuru, Tomohito; Itakura, Mitsuhiro

Materials Transactions, 64(11), p.2553 - 2559, 2023/11

https://doi.org/10.2320/matertrans.MT-M2023106

We attempted to calculate the hydrogen trapping energies on the incoherent interfaces of MgZn precipitates and MgSi crystallites in aluminum alloys from first-principles calculations. Since the unit cell containing the incoherent interface does not satisfy the periodic boundary condition, resulting in a discontinuity of crystal blocks, the hydrogen trapping energy was calculated in a region far from the discontinuity (vacuum) region. We found considerable trapping energies for hydrogen atoms at the incoherent interfaces consisting of assumed atomistic arrangement. We also conducted preliminary calculations of the reduction in the cohesive energy by hydrogen trapping on the incoherent interfaces of MgSi in the aluminum matrix.

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

https://doi.org/10.5006/4300

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.

Identification of hydrogen trapping in aluminum alloys 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

https://doi.org/10.1007/s11661-023-07024-w

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 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 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.

Atomistic weak interaction criterion for the specificity of liquid metal embrittlement

Yamaguchi, Masatake; Tsuru, Tomohito; Itakura, Mitsuhiro; Abe, Eiji*

Scientific Reports (Internet), 12(1), p.10886_1 - 10886_7, 2022/07

https://doi.org/10.1038/s41598-022-10593-2

no abstracts in English