GRAIN-BOUNDARY DIFFUSION OF COBALT IN POLYCRYSTALLINE TUNGSTEN

The radiometric sectioning method was used to study diffusion of Co-57 along the grain boundaries of polycrystalline tungsten in the temperature range from 780 to 1980 K. At T-1280 K (-0.35 T(m) where T(m) is the melting point of the matrix element) the temperature dependence of the grain boundary diffusion (GBD) data exhibits a break which is analogous to the one observed for GBD in silver polycrystals. This break is most likely due to the fact that the mechanism of diffusant "pumping" from the grain boundary to the bulk changes at low temperatures.