GRAIN-BOUNDARY ENHANCED DIFFUSION FROM INSTANTANEOUS SOURCE IN SMALL-GRAIN DEEP-PENETRATION CONDITION

A grain-boundary diffusion equation was derived for small-grain deep-p enetration diffusion and solved for the instantaneous source condition , where the flux from the grain boundary into grains was taken into ac count as a time-dependent function. From the solution of the equation, the average concentration distribution along the diffusion direction was derived to describe the concentration distribution to be determine d for polycrystal by scanning technique with electron probe X-ray micr oanalyzer (EPMA).