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 language | English |
|---|---|
| Pages (from-to) | 756-760 |
| Number of pages | 5 |
| Journal | Materials Transactions |
| Volume | 46 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - Apr 2005 |
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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 journal › Article
}
TY - JOUR
T1 - Hydrogen-promoted grain boundary embrittlement and vacancy activity in metals
T2 - Insights from ab initio total energy calculatons
AU - Geng, Wen Tong
AU - Freeman, Arthur J
AU - Olson, Gregory B.
AU - Tateyama, Yoshitaka
AU - Ohno, Takahisa
PY - 2005/4
Y1 - 2005/4
N2 - 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.
AB - 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.
KW - Ab initio calculation
KW - Grain boundary embrittlement
KW - Hydrogen embrittlement
KW - Vacancy activity
UR - http://www.scopus.com/inward/record.url?scp=20844453209&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=20844453209&partnerID=8YFLogxK
U2 - 10.2320/matertrans.46.756
DO - 10.2320/matertrans.46.756
M3 - Article
AN - SCOPUS:20844453209
VL - 46
SP - 756
EP - 760
JO - Materials Transactions
JF - Materials Transactions
SN - 0916-1821
IS - 4
ER -