An experimental study was made of a new phenomenon which accompanied grain boundary interdiffusion. That is, hole channel formation along grain boundaries. The samples used were plates of homogeneous Cu-5at%Sn alloy, which were annealed at 800C in purified H. Porous zones were found, with grain-boundary hole channels oriented perpendicularly to the surface and essentially equidistant from one another. Porous-zone propagation, and average pore-size growth in the early stages of annealing, obeyed a parabolic law. The observed processes were caused by the nucleation and growth of a Cu3Sn phase at the free surface. The new phase then functioned as a so-called diffusion pump and transferred Sn atoms from the alloy and towards the growing compound layer. The grain-boundary channel formation was described as being a relaxation process which accompanied the grain-boundary interdiffusion of Sn and Cu atoms with unequal partial diffusion coefficients (DSn > DCu). Excess vacancies which appeared at the grain boundaries, due to the inequality between DSn and DCu, were absorbed by bulk and grain-boundary sinks and tensile stresses appeared near to the grain boundaries; thus stimulating hole channels or groove formation.

Grain Boundary Channel Formation During Interdiffusion in Alloys. L.N.Paritskaya, V.V.Bogdanov, Y.Kaganovskii, W.Gust: Interface Science, 2002, 10[4], 297-302