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Kamada, Masaki*; Yoshida, Takuma*; Sugita, Tsukasa*; Okumura, Keisuke
Nihon Genshiryoku Gakkai-Shi ATOMO
, 66(2), p.83 - 86, 2024/02
no abstracts in English
5 (012) symmetrical tilt grain boundary; A First-principles studyYamaguchi, Masatake; Shiga, Motoyuki; Kaburaki, Hideo
Journal of Physics; Condensed Matter, 16(23), p.3933 - 3956, 2004/06
Times Cited Count：89 Percentile：92.94(Physics, Condensed Matter)A series of non-transition elements bound to the Ni 5(012) symmetrical tilt grain boundary (GB) and the (012) free surface (FS) systems has been studied by first-principles calculation using WIEN2k code. The multilayer relaxations in presence/absence of the solutes are determined by the force minimization. The binding energies at some GB/FS/bulk sites including both interstitial and substitutional sites are calculated for all the non-transition elements between 
H and 
Rn. The GB/FS segregation energy is obtained by calculating the binding energy difference between the GB/FS site and the bulk site. The embrittling potency energy is obtained by calculating the difference between the GB and FS segregation energies based on Rice-Wang model. Our results show that most of the non-transition elements have negative GB/FS segregation energies. Here, this means that there exists a segregation site in the GB/FS. The embrittling potency energies are positive for most of the solutes. However, some exceptions like Be, B, C, and Si having negative and large embrittling potency can enhance the GB cohesion. Our results are found to be consistent with the experimental findings.
5(012) tilt grain boundaryYamaguchi, Masatake; Shiga, Motoyuki; Kaburaki, Hideo
Journal of the Physical Society of Japan, 73(2), p.441 - 449, 2004/02
Times Cited Count：23 Percentile：71.37(Physics, Multidisciplinary)The electronic structures of 5(012) symmetrical tilt grain boundary (GB) and (012) free surface (FS) systems for nickel including hydrogen are calculated by the full-potential linearized augmented plane wave method with the generalized gradient approximation. The difference of the binding energies between the 5(012)GB/FS site and the inner bulk site is obtained as the GB/FS segregation energy, and the difference between GB and FS segregation energies as the embrittling potency energy. The segregation position of hydrogen atom is determined by the force minimization. We find that hydrogen atom prefers 5(012)GB to inner bulk energetically by about 0.3 eV/H, while it prefers (012)FS to the GB by about 0.3-0.4 eV/H. The open space at GB may be occupied by an additional interstitial Ni atom since it increases the GB energy by only about 10%. In this case, the GB segregation energy of hydrogen reduces, which makes the segregation difficult. The calculated zero-point energies of hydrogen at inner bulk, GB, and FS sites are within 0.12-0.16eV/H.
Tsukada, Takashi
Zairyo To Kankyo, 52(2), p.66 - 72, 2003/02
Irradiation assisted stress corrosion cracking (IASCC) is a potential failure mode suffered by the core-components of austenitic stainless steels in the aged light-water reactor (LWR), which is the intergranular type cracking caused by synergistic effects of neutron/gamma radiation and chemical environment. Effects of radiation on the materials and high-temperature water are discussed in this paper to understand IASCC phenomenon from a mechanistic viewpoint. It is essential to elucidate the radiation-induced microcompositional and microstructural changes in the alloy for mechanistic and predictive investigations of IASCC. Although grain boundary segregations of alloying and impurity elements are significant factors affecting IASCC, it has been considered that the radiation-induced microstructural and mechanical changes of materials play critical roles in IASCC. For mechanistic understanding of IASCC, further fundamental research works with experimental and theoretical approaches are needed. Efforts directed to the researches at the Japan Atomic Energy Research Institute are also described.
Kameda, Jun*; Nishiyama, Yutaka; Bloomer, T. E.*
Surface and Interface Analysis, 31(7), p.522 - 531, 2001/07
Times Cited Count：10 Percentile：28.89(Chemistry, Physical)This study describes intergranular segregation and embrittlement in several model ferritic alloys doped with Mn, P, S and/or Cu subjected to neutron irradiation, irradiation-equivalent thermal ageing (ETA) and post-irradiation annealing (PIA). Neutron irradiation produced a larger amount of intergranular P segregation than S segregation. Intergranular C segregation remained small in all the as-irradiated alloys. A PIA study has shown that the P segregation in P-doped alloys subjected to lower temperature PIA proceeds via mobile P-interstitial complexes while the S segregation is controlled by vacancy-enhanced diffusion. The mechanisms of non-equilibrium intergranular segregation induced by neutron irradiation are discussed in light of coupled fluxes of point defects and impurities, and changes in the segregation capacity of grain boundaries. Small punch tests demonstrated how the impurity segregation or desegregation and hardening or softening induced by the irradiation, ETA and PIA influence intergranular embrittlement in the various ferritic alloys.
/Si InterfacesOshima, Masaharu*; *; Ono, Kanta*; Fujioka, Hiroshi*; *; Baba, Yuji; Yoshii, Kenji; Sasaki, Teikichi
Journal of Electron Spectroscopy and Related Phenomena, 88-91, p.603 - 607, 1998/00
Times Cited Count：5 Percentile：25.68(Spectroscopy)no abstracts in English
Nishiyama, Yutaka; Fukaya, Kiyoshi; Suzuki, Masahide; Eto, Motokuni; *
Small Specimen Test Techniques; ASTM STP 1204, p.16 - 26, 1993/00
no abstracts in English
Journal of the Physical Society of Japan, 17(2), p.322 - 325, 1962/00
Times Cited Count：220no abstracts in English
Hata, Kuniki; Nagai, Yasuyoshi*; Nishiyama, Yutaka
no journal, ,
no abstracts in English
