The grain boundary diffusion products were determined for 195Au migrating via various boundaries. A series of 12 symmetrical [001] tilt boundaries was used. These were precisely characterized by using the Kossel technique, and 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. This was true of all of the temperatures which were investigated. 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

Table 36

Product of the Segregation Factor, Grain Boundary Diffusion

Coefficient, and Grain Boundary Width, for Au in Cu