Effects of nickel diffusion at 1473K on the structural degradation of Ni3Al intermetallics obtained by self-propagating synthesis were investigated. It was shown that, in non-homogenized Ni3Al, effects of grain-boundary migration and recrystallization induced by grain-boundary diffusion of nickel were observed. In the regions where migration and recrystallization occur, Ni atoms were left by migrating grain boundaries, which results in a supersaturation and subsequent decomposition of the intermetallic Y phase and the formation of a two-phase mixture (γ′ + γ). It was supposed that the main causes for the occurrence of diffusion-induced grain-boundary migration and recrystallization were the enhancement of the driving forces of the usual migration and recrystallization as well as the increase of grain-boundary mobility due to the development of an osmotic pressure at grain boundaries.
Nickel-Diffusion-Induced Grain-Boundary Migration and Recrystallization in Ni3Al Intermetallics Produced by SHS. Marvina, L.A., Marvin, V.B.: Physics of Metals and Metallography, 1996, 81[2], 194-9
Table 30
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 |
continued
Table 30 (continued)
Grain boundary diffusion of Ni in Ni3Al-based alloys
Alloy | Temperature (K) | D (m3/s) |
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 |
Figure 27
Grain-boundary diffusion of 63Ni in B-doped Ni3Al
Table 31
Diffusion of 63Ni in Ni3Al alloys
Temperature (K) | Alloy | D(m2/s) |
1183.8 | Ni74.89Al25.11 | 1.90 x 10-17 |
1183.8 | Ni74.70Al20.17Ge5.13 | 5.82 x 10-17 |
1183.8 | Ni75.03Al9.96Ge15.01 | 2.93 x 10-16 |
1183.8 | Ni74.67Al6.97Ge18.36 | 5.26 x 10-16 |
1183.8 | Ni75.14Ge24.86 | 1.87 x 10-15 |
1282.5 | Ni74.89Al25.11 | 1.88 x 10-16 |
1282.5 | Ni74.70Al20.17Ge5.13 | 5.66 x 10-16 |
1282.5 | Ni75.03Al9.96Ge15.01 | 2.85 x 10-15 |
1282.5 | Ni74.67Al6.97Ge18.36 | 4.20 x 10-15 |
1282.5 | Ni75.14Ge24.86 | 1.20 x 10-14 |
1373 | Ni74.89Al25.11 | 9.64 x 10-16 |
1373 | Ni74.70Al20.17Ge5.13 | 3.34 x 10-15 |
1373 | Ni75.03Al9.96Ge15.01 | 1.63 x 10-14 |
1373 | Ni74.67Al6.97Ge18.36 | 2.50 x 10-14 |
1373 | Ni75.14Ge24.86 | 3.74 x 10-14 |