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Title: Ab Initio Modeling of Bulk and Intragranular Diffusion in Ni Alloys

importance for understanding mechanisms of grain boundary (GB) oxidation causing environmental degradation and cracking of Ni-base structural alloys. In this study, first-principles calculations of vacancy-mediated diffusion are performed across a wide series of alloying elements commonly used in Ni-based superalloys, as well as interstitial diffusion of atomic oxygen and sulfur in the bulk, at the (111) surface, <110> symmetric tilt GBs of Ni corresponding to model low- (Σ=3/(111)) and high-energy (Σ=9/(221)) GBs. A substantial enhancement of diffusion is found for all species at the high-energy GB as compared to the bulk and the low-energy GB, with Cr, Mn and Ti exhibiting remarkably small activation barriers (<0.1 eV; ~10 times lower than in the bulk). Calculations also show that the bulk diffusion mechanism and kinetics differ for oxygen and sulfur, with oxygen having a faster mobility and preferentially diffusing through the tetrahedral interstitial sites in Ni matrix where it can be trapped in a local minimum.
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Publication Date:
OSTI Identifier:
Report Number(s):
48274; KC0202040
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry Letters, 6(9):1618-1623
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
Country of Publication:
United States
Environmental Molecular Sciences Laboratory