The parameter which described the chemical diffusion of Ag along the tilt axes of a series of [001] symmetrical tilt boundaries, in the Au-Ag system, was studied as a function of temperature and tilt angle at relatively low temperatures. Sixteen boundaries were studied by using a newly developed surface accumulation method. The parameter was found to vary quite smoothly as a function of tilt angle. That is, there were no sharp minima or cusps at low- misorientations. This behavior was consistent with the structural unit model. The activation energies were found to be smooth functions of the tilt angle, and to range from 0.70 to 0.85eV. The pre-exponential factors in the Arrhenius expression for the grain boundary diffusion parameter were some 3 orders of magnitude smaller than many reported values for diffusion at higher temperatures. In the case of a typical boundary, the diffusivity was described by:

D (m3/s) = 4.8 x 10-18exp[-0.68(eV)/kT]

Q.Ma, R.W.Balluffi: Acta Metallurgica et Materialia, 1993, 41[1], 133-41