The self-diffusion of 63Ni along boundaries in Ni-25.2Al, Ni-24.9Al-4.8W, Ni-24.2Al-4.7Cr, Ni-19.3Al-4.5Hf and Ni-27.6Al-4.9at%Co was investigated by using radiotracer and serial sectioning techniques. By using the near-surface parts of the profiles, which reflected lattice diffusion, the volume diffusion coefficients were estimated (table 25). In the case of pure Ni3Al, the agreement of the high-temperature results with published data was good. By using the bulk diffusion results, and by analyzing the tails of the measured profiles, grain-boundary diffusivities were calculated. It was found that these (table 26) could be described by the relationships:
Ni-Al (1273-1073K): D (m3/s) = 1 x 10-12 exp[-195(kJ/mol)/RT]
Ni-Al-Hf (1373-1023K): D (m3/s) = 6.4 x 10-12 exp[-219(kJ/mol)/RT]
Ni-Al-W (1373-1023K): D (m3/s) = 3.3 x 10-12 exp[-217(kJ/mol)/RT]
Ni-Al-Co (1273-1023K): D (m3/s) = 6.8 x 10-13 exp[-189(kJ/mol)/RT]
Ni-Al-Cr (1323-1023K): D (m3/s) = 1.8 x 10-9 exp[-265(kJ/mol)/RT]
By using the bulk and grain-boundary diffusion data, the boundary energies were estimated by using the Borisov semi-empirical relationship. It was noted that the calculated energies exhibited a marked positive temperature dependence.
N.P.Zulina, E.V.Bolberova, I.M.Razumovskii: Acta Materialia, 1996, 44[9], 3625-31
Table 25
Bulk Diffusion of Ni in Ni3Al-Based Alloys
Alloy |
Temperature (K) |
D (m2/s)
|
Ni-Al |
1323 |
4.3 x 10-16 |
Ni-Al | 1273 | 1.6 x 10-16 |
Ni-Al | 1173 | 1.4 x 10-17 |
Ni-Al | 1073 | 1.7 x 10-18 |
Ni-Al | 973 | 3.2 x 10-19 |
Ni-Al-Hf | 1373 | 8.0 x 10-16 |
Ni-Al-Hf | 1323 | 3.3 x 10-16 |
Ni-Al-Hf | 1273 | 7.6 x 10-17 |
Ni-Al-Hf | 1223 | 3.1 x 10-17 |
Ni-Al-Hf | 1173 | 6.7 x 10-18 |
Ni-Al-Hf | 1123 | 3.2 x 10-18 |
Ni-Al-Hf | 1073 | 8.0 x 10-19 |
Ni-Al-Hf | 1023 | 1.1 x 10-19 |
Ni-Al-W | 1373 | 3.4 x 10-16 |
Ni-Al-W | 1323 | 1.5 x 10-16 |
Ni-Al-W | 1273 | 5.4 x 10-17 |
Ni-Al-W | 1223 | 2.0 x 10-17 |
Ni-Al-W | 1173 | 4.7 x 10-18 |
|
|
|
|
|
|
Ni-Al-W | 1123 | 1.8 x 10-18 |
Ni-Al-W | 1073 | 3.5 x 10-19 |
Ni-Al-W | 1023 | 8.1 x 10-20 |
Ni-Al-Co | 1323 | 4.0 x 10-16 |
Ni-Al-Co | 1273 | 2.0 x 10-16 |
Ni-Al-Co | 1223 | 4.3 x 10-17 |
Ni-Al-Co | 1173 | 1.6 x 10-17 |
Ni-Al-Co | 1123 | 4.4 x 10-18 |
Ni-Al-Co | 1073 | 2.1 x 10-18 |
Ni-Al-Co | 1023 | 2.0 x 10-19 |
Ni-Al-Cr | 1323 | 4.3 x 10-16 |
Ni-Al-Cr | 1273 | 2.1 x 10-16 |
Ni-Al-Cr | 1223 | 4.3 x 10-17 |
Ni-Al-Cr | 1173 | 2.0 x 10-17 |
Ni-Al-Cr | 1123 | 4.3 x 10-18 |
Ni-Al-Cr | 1073 | 9.0 x 10-19 |
Ni-Al-Cr | 1023 | 3.3 x 10-19
|
Table 26
Grain Boundary Diffusion of Ni in Ni3Al-Based Alloys
Alloy |
Temperature (K) |
D (m3/s)
|
Ni-Al |
1273 |
1.2 x 10-20 |
Ni-Al | 1173 | 1.7 x 10-21 |
Ni-Al | 1073 | 3.8 x 10-22 |
Ni-Al | 973 | 1.0 x 10-22 |
Ni-Al-Hf | 1373 | 3.3 x 10-20 |
Ni-Al-Hf | 1323 | 1.6 x 10-20 |
Ni-Al-Hf | 1273 | 7.0 x 10-21 |
Ni-Al-Hf | 1223 | 2.2 x 10-21 |
Ni-Al-Hf | 1173 | 9.9 x 10-22 |
Ni-Al-Hf | 1123 | 4.0 x 10-22 |
Ni-Al-Hf | 1073 | 1.7 x 10-22 |
Ni-Al-Hf | 1023 | 4.3 x 10-23 |
Ni-Al-W | 1373 | 1.9 x 10-20 |
Ni-Al-W | 1323 | 1.1 x 10-20 |
|
|
|
|
|
|
Ni-Al-W | 1273 | 3.7 x 10-21 |
Ni-Al-W | 1223 | 1.8 x 10-21 |
Ni-Al-W | 1173 | 7.5 x 10-22 |
Ni-Al-W | 1123 | 2.3 x 10-22 |
Ni-Al-W | 1073 | 1.1 x 10-22 |
Ni-Al-W | 1023 | 2.9 x 10-23 |
Ni-Al-Co | 1273 | 1.2 x 10-20 |
Ni-Al-Co | 1223 | 5.5 x 10-21 |
Ni-Al-Co | 1173 | 2.6 x 10-21 |
Ni-Al-Co | 1123 | 1.2 x 10-21 |
Ni-Al-Co | 1073 | 2.9 x 10-22 |
Ni-Al-Co | 1023 | 1.8 x 10-22 |
Ni-Al-Cr | 1323 | 6.1 x 10-20 |
Ni-Al-Cr | 1273 | 2.6 x 10-20 |
Ni-Al-Cr | 1223 | 7.8 x 10-21 |
Ni-Al-Cr | 1173 | 3.1 x 10-21 |
Ni-Al-Cr | 1123 | 9.1 x 10-22 |
Ni-Al-Cr | 1073 | 1.6 x 10-22 |
Ni-Al-Cr | 1023 | 6.5 x 10-23
|