Grain boundary diffusion and solute segregation in polycrystals and oriented bicrystals

Measurements of solute GB diffusion in Cu and Ag polycrystals were carried out in Harrisons type-B and type-C kinetic regime using Se-75, Au-195, Ni-63 radioisotopes. In the B-regime at high temperatures, the GB diffusion parameter s delta D-GB was determined (s being the GB segregation factor, delta the GB width and D-GB the GB diffusion coefficient), while in the C-regime at low temperatures DGB values were measured directly. The investigations of these differently behaving solute - solvent systems on Cu and Ag basis yield information on solute GB diffusion and segregation in relation to solute - solvent atomic binding and solute vacancy interaction in the bulk and in GBs. The GB diffusion of Cu-64 and Au-195 in a series of near Sigma = 5, Theta = 36.9 degrees (310) [001] Cu tilt GBs and of Ge-71 in a series of near Sigma = 7, Theta = 38.2 degrees (12(3) over bar) [111] Al tilt GBs in dependence on the tilt angle Theta and on the temperature was studied. A characteristic minimum in the GB diffusion parameter and a maximum in the activation energy was observed at the ideal CSL GBs.