Tp. Swiler et al., HETEROGENEOUS DIFFUSION EFFECTS IN POLYCRYSTALLINE MICROSTRUCTURES, Materials science & engineering. A, Structural materials: properties, microstructure and processing, 238(1), 1997, pp. 85-93
Diffusion in polycrystalline microstructures is influenced by two fact
ors that are not considered in a simple continuum material description
. These are kinetic effects, where the diffusivities of grain boundari
es differ from those of the grains, and free-energy effects, where the
driving force for diffusion is dependent on a free energy function th
at includes the phase of the diffusion medium as well as its compositi
on. Simulation studies of kinetic diffusion effects in two-dimensional
polycrystalline microstructures obtained from the Potts model have sh
own that the compositional gradients resulting from these effects are
transitory in nature, and that average diffusivities are dependent on
microstructural features such grain size, diffusion bottlenecks in gra
in boundary paths, and model lattice artifacts. Similar studies of fre
e-energy effects using the phase-field model show that metastable grai
n boundary segregation of components occurs, and that the rate and nat
ure of grain growth can be influenced by an imposed composition gradie
nt. Collectively, these studies show that the two simulation technique
s, finite-difference solutions of fast grain boundary diffusion in the
polycrystalline microstructures obtained from the Potts-model and pha
se-field model solutions of diffusion in evolved and evolving microstr
uctures with spatially dependent chemical potentials, are complementar
y in studying diffusional effects in polycrystalline microstructures.
(C) 1997 Elsevier Science S.A.