Calculation of Diffusion Penetration Curves for Surface and Grain Boundary Diffusion

Diffusion in solids is known to occur along grain boundaries and over free surfaces more rapidly than through the interiors of crystals. In order to facilitate quantitative investigation of grain boundary and surface diffusion, a mathematical analysis of the problem has been completed, assuming that grain boundary diffusion is analogous to the diffusion of heat along a thin copper foil imbedded in cork. The calculated diffusion-penetration relationship for grain boundary diffusion is shown to agree with the experimentally determined grain boundary self-diffusion of silver.