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.
Ab Initio Modeling of Bulk and Intragranular Diffusion in Ni Alloys.
Abstract:
Citation:
Alexandrov VY, ML Sushko, DK Schreiber, SM Bruemmer, and KM Rosso.2015."Ab Initio Modeling of Bulk and Intragranular Diffusion in Ni Alloys."Journal of Physical Chemistry Letters 6(9):1618-1623. doi:10.1021/acs.jpclett.5b00177
Capabilities:
Facility:
Science Theme:
Instruments:
Volume:
6
Issue:
9
Pages:
1618-1623
Publication year:
2015