Hydrogen-promoted grain boundary embrittlement and vacancy activity in metals

Insights from ab initio total energy calculatons

Wen Tong Geng, Arthur J Freeman, Gregory B. Olson, Yoshitaka Tateyama, Takahisa Ohno

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The rapid diffusion of H in metals permits an easy segregation to the grain boundary and an easy trapping to the vacancy. H-induced intergranular embrittlement in metals such as Fe and Ni is generally a result of coalition of segregated H and other embrittling impurities at the grain boundary. Ab initio total energy calculations based on the density functional theory have shown that H alone can also weaken the cohesion across the grain boundary. The stronger binding of H with a free surface than with a grain boundary, which results in grain boundary embrittlement according to the Rice-Wang theory, can be ascribed to its monovalency. New tensile experiments point to a H-enhanced vacancy contribution to the increased susceptibility of steel to H embrittlement. Ab initio density functional calculations on the energetics of interstitial H, vacancy, and H-monovacancy complexes (VacHn) in bcc Fe have shown that the predominant complex under ambient condition of H pressure is VacH2, not VacH6 as previously suggested by effective-medium theory calculations. The linear structure of VacH2 clusters, a consequence of repulsion between negatively charged H atoms, facilitates the formation of linear and tabular vacancy clusters and such anisotropic clusters may lead to void or crack nucleation on the cleavage planes. On the other hand, the H-induced increase of vacancy cluster formation energy is a support of the experimentally observed enhancement of dislocation mobility in the presence of H, which, through the mechanism of H-enhanced localized plasticity, makes fracture easier.

Original languageEnglish
Pages (from-to)756-760
Number of pages5
JournalMaterials Transactions
Volume46
Issue number4
DOIs
Publication statusPublished - Apr 2005

Fingerprint

embrittlement
Embrittlement
Vacancies
Hydrogen
Grain boundaries
grain boundaries
Metals
hydrogen
metals
Density functional theory
energy
cohesion
Steel
rice
energy of formation
plastic properties
Plasticity
voids
cleavage
interstitials

Keywords

  • Ab initio calculation
  • Grain boundary embrittlement
  • Hydrogen embrittlement
  • Vacancy activity

ASJC Scopus subject areas

  • Materials Science(all)
  • Metals and Alloys

Cite this

Hydrogen-promoted grain boundary embrittlement and vacancy activity in metals : Insights from ab initio total energy calculatons. / Geng, Wen Tong; Freeman, Arthur J; Olson, Gregory B.; Tateyama, Yoshitaka; Ohno, Takahisa.

In: Materials Transactions, Vol. 46, No. 4, 04.2005, p. 756-760.

Research output: Contribution to journalArticle

Geng, Wen Tong ; Freeman, Arthur J ; Olson, Gregory B. ; Tateyama, Yoshitaka ; Ohno, Takahisa. / Hydrogen-promoted grain boundary embrittlement and vacancy activity in metals : Insights from ab initio total energy calculatons. In: Materials Transactions. 2005 ; Vol. 46, No. 4. pp. 756-760.
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