The problem of the compensation effect (linear dependence of the pre-exponential factor for grain boundary diffusion upon the activation energy) for grain boundary diffusion was considered. Specific features (segregation factor, grain boundary width) of grain boundary diffusion as a thermally activated process were included. A special diffusion experiment was designed in order to estimate the contributions made by the individual components of the triple product, KδDb. The experiment was performed using bicrystals. The variation of the grain boundary width, and a value of the segregation factor, due to grain boundary structural change, were estimated. It was concluded that Db was the main grain-boundary structure-sensitive parameter in the triple product. This permitted the grain boundaries in Al bicrystals to be considered to constitute a series of uniform objects, and to describe the kinetics of grain boundary diffusion in terms of the compensation temperature, Tc, and a so-called barrier phase. The values of Tc for the grain boundary diffusion of Zn and Ge in Al bicrystals were essentially the same, and were equal to 709 and 706K, respectively.

Compensation Effect for Grain Boundary Diffusion in a Bicrystalline Experiment. A.N.Aleshin, R.G.Faulkner, D.A.Molodov, L.S.Shvindlerman: Interface Science, 2002, 10[1], 5-12