Monte Carlo and analytical modeling of the effects of grain boundaries on diffusion kinetics
- Lehigh Univ., Bethlehem, PA (United States). Dept. of Materials Science and Engineering
The authors examine quantitatively the impact of a grain boundary on the kinetics of diffusion in a concentrated lattice gas. In the model the lattice gas particles move via Kawasaki dynamics on the sites of a simple cubic lattice in which a high-diffusivity slab (i.e., grain boundary) has been embedded. Their motion is constrained such that multiple occupancy of a site is forbidden. By examining various subsets of particles, it is found that a temporal bias exists and can be explained in terms of approximate rate equations which embody the dynamical inhomogeneity of the system. It is observed that particles tend to migrate toward the grain boundary region for a definite period of time. As it has been useful experimentally to relate bulk and grain boundary diffusivities from an analysis of concentration profiles, the authors identify analogous quantities here which relate these diffusivities in the simulations. In particular, by identifying correlations between particle position and site transition frequencies, they have constructed an accurate analytical model of diffusion kinetics that is applicable both near to and far from grain boundaries. It is found that a volume-weighted diffusivity is not appropriate normal to the boundary due to dynamical correlations.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 271791
- Journal Information:
- Acta Materialia, Vol. 44, Issue 6; Other Information: PBD: Jun 1996
- Country of Publication:
- United States
- Language:
- English
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