Direct experimental observation of accelerated Zn diffusion along triple junctions in Al

It is agreed that the diffusion penetration at triple junctions is higher, than the diffusion penetration at grain boundaries. However, the authentic experimental data confirming this speculative representation were absent till now. The aim of this work is to obtain the direct experimental data on triple junction diffusion. The technique of preparation of aluminum samples with large grains with so called bamboo structure and with triple junctions spread through the thickness of sample is developed. The layer of zinc was coated on sample surface using chemical method. Then samples were diffusion annealed in vacuum. The developed technique of mechanical removal of layers 5–10 μ thick allowed to observe individual triple junctions at different depths from the initial layer of zinc. With the use of the microanalysis the zinc concentration in grain boundaries near to the triple junctions was obtained. In result the ratio of triple junction (DTJ) to grain boundary (DGB) diffusion coefficients was estimated, which approximated to 103 at 280°C.