The migration of Cr in [1¯01]/[112] symmetrical body-centered cubic bicrystals of Nb was investigated at temperatures ranging from 950 to 1197C (table 20). The tilt angles ranged from 2 to 21. When the tilt angle was less than 17, the activation energy was independent of the angle; with an average value of 181.2kJ/mol (table 21). This value was equal to about half of that for lattice diffusion. The grain boundary diffusion coefficients were greater, than the lattice diffusion coefficients, by 5 or 6 orders of magnitude. They also varied linearly as the sine of half of the tilt angle. This behavior was consistent with a dislocation-pipe model. These results were generally consistent with those for face-centered cubic bicrystals.

X.M.Li, Y.T.Chou: Philosophical Magazine A, 1996, 73[5], 1303-11

Table 20

Grain Boundary Diffusivity of Cu in [1¯01]/[112] Nb Bicrystals

as a Function of Temperature and Tilt Angle

Table 21

Parameters for the Grain Boundary Diffusion

of Cr in [1¯01]/[112] Nb Bicrystals