Energetic Study of Helium Cluster Nucleation and Growth in 14YWT through First Principles

First principles calculations have been performed to energetically investigate the helium cluster nucleation, formation and growth behavior in the nano-structured ferritic alloy 14YWT. The helium displays strong affinity to the oxygen:vacancy (O:Vac) pair. By investigating various local environments...

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Bibliographic Details
Published in:Materials 2016-01, Vol.9 (1), p.17-17
Main Authors: Gan, Yingye, Zhao, Huijuan, Hoelzer, David T, Yun, Di
Format: Article
Language:English
Subjects:
Alloys
Atomic properties
Bubbles
Clusters
Energy costs
first principles theory
formation criteria
Grain boundaries
Helium
helium bubbles
Investigations
Lattice vacancies
MATERIALS SCIENCE
Nanostructure
nanostructured ferritic alloys
Nucleation
Steels
Titanium
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Summary:First principles calculations have been performed to energetically investigate the helium cluster nucleation, formation and growth behavior in the nano-structured ferritic alloy 14YWT. The helium displays strong affinity to the oxygen:vacancy (O:Vac) pair. By investigating various local environments of the vacancy, we find that the energy cost for He cluster growth increases with the appearance of solutes in the reference unit. He atom tends to join the He cluster in the directions away from the solute atoms. Meanwhile, the He cluster tends to expand in the directions away from the solute atoms. A growth criterion is proposed based on the elastic instability strain of the perfect iron lattice in order to determine the maximum number of He atoms at the vacancy site. We find that up to seven He atoms can be trapped at a single vacancy. However, it is reduced to five if the vacancy is pre-occupied by an oxygen atom. Furthermore, the solute atoms within nanoclusters, such as Ti and Y, will greatly limit the growth of the He cluster. A migration energy barrier study is performed to discuss the reduced mobility of the He atom/He cluster in 14YWT.
ISSN:1996-1944
1996-1944
DOI:10.3390/ma9010017