It was recalled that a combination of so-called B- and C-type solute grain boundary diffusion measurements was a unique and reliable tool for the determination of the solute segregation factor for the true dilute limit conditions. A series of such measurements with different solutes in the same high purity Cu material revealed comprehensive quantitative information on the solute segregation behaviour. Specially designed radiotracer experiments on bicrystals provided valuable information on non-linear solute segregation, and a complete solute segregation isotherm could be determined. The strong solute segregation could produce new effects. The grain boundary wetting transition in the Bi–Cu system was investigated by radiotracer diffusion. A pronounced increase in grain boundary diffusivity was observed in the two-phase (solid + liquid) region of the corresponding phase diagram; with the grain-boundary diffusivity of Cu being similar to the diffusion rate in a liquid. Such a grain boundary diffusion enhancement existed even in the single phase (solid solution in Cu) region revealing the existence of a pre-wetting grain boundary phase transition in this system.

Radiotracer Investigation of Diffusion, Segregation and Wetting Phenomena in Grain Boundaries. S.Divinski, C.Herzig: Journal of Materials Science, 2009, 43[11], 3900-7