The impact of a complex microstructure on polycrystalline diffusion was investigated using both numerical and analytical methods. In particular, the diffusion equation was numerically integrated using the finite-difference method to obtain the concentration profile for a diffusant in a simplified microstructural representation. The methodology was first validated for an idealized model of diffusion in a prototypical, single grain-boundary system and then applied to a Voronoi model of a microstructure resulting from homogeneous nucleation and growth. The diffusive behavior was quantified by obtaining uptake curves as a function of time for different ratios of grain boundary to lattice diffusivities. Such curves could be used to estimate an unknown grain-boundary diffusivity, given certain microstructural assumptions. Finally, approximate analytical equations describing a diffusant uptake in polycrystalline microstructural models were developed and found to agree well with the numerical results.

Impact of Microstructure on Grain-Boundary Diffusion in Polycrystals. K.Bedu-Amissah, J.M.Rickman, H.M.Chan, M.P.Harmer: Journal of Applied Physics, 2005, 98[6], 063511 (6pp)