Grain boundary diffusion was determined for 195Au migrating via various boundaries. A series of 12 symmetrical [001] tilt boundaries was used. These had tilt angles which were near to the ideal 36.9  = 5 (310) coincidence site lattice boundary; with a spread of 6. It was found that, at homologous temperatures that ranged from 0.48 to 0.78, the orientation dependence of the diffusion product exhibited a characteristic cusp at an orientation which was slightly below the ideal  = 5 coincidence site lattice grain boundary orientation. The activation enthalpy for grain boundary diffusion exhibited a marked orientation dependence at lower temperatures. With increasing temperature, a negative deviation from linear Arrhenius behavior was observed and the orientation dependence of the activation enthalpy for grain boundary diffusion disappeared. It was concluded that these results indicated the occurrence of a temperature-induced change in the grain boundary structure. The data for high temperatures could be described by:

D (m3/s) = 10-17exp[-40(kJ/mol)/RT]

E.Budke, C.Herzig, S.Prokofiev, L.S.Shvindlerman: Materials Science Forum, 1996, 207-209, 465-8