The migration of Cr in [1¯01]/[112] symmetrical body-centered cubic bi-crystals of Nb was investigated at temperatures ranging from 950 to 1197C (table 136). 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 137). 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 136
Grain Boundary Diffusivity of Cu in [1¯01]/[112] Nb Bicrystals
as a Function of Temperature and Tilt Angle
Temperature (C) | Tilt Angle () | sD (m3/s) |
950 | 2 | 9.97 x 10-24 |
1197 | 2 | 2.02 x 10-22 |
950 | 5 | 1.15 x 10-23 |
1197 | 5 | 2.32 x 10-22 |
950 | 10 | 1.40 x 10-23 |
1197 | 10 | 2.76 x 10-22 |
950 | 13 | 1.56 x 10-23 |
1197 | 13 | 3.11 x 10-22 |
950 | 17 | 1.68 x 10-23 |
1197 | 17 | 3.34 x 10-22 |
950 | 21 | 1.61 x 10-23 |
1197 | 21 | 8.26 x 10-22 |
Table 137
Parameters for the Grain Boundary Diffusion
of Cr in [1¯01]/[112] Nb Bicrystals
Tilt Angle () | Q (kJ/mol) | sD (m3/s) |
2 | 182.8 | 5.88 x 10-16 |
5 | 179.3 | 5.33 x 10-16 |
8 | 179.7 | 5.76 x 10-16 |
10 | 179.1 | 6.56 x 10-16 |
13 | 182.8 | 9.87 x 10-16 |
17 | 183.3 | 1.12 x 10-15 |
21 | 226.3 | 6.63 x 10-14 |