Possible temperature dependence of the activation energy for grain boundary diffusion in metals
The apparent activation energy for existing grain boundary diffusion data shows a tendency to decrease with decreasing temperature. Such a decrease may conceivably be due to at least two causes: (1) The grain boundary diffusion must involve several different types of atomic jumps in the core region, each of which is characterized by a different activation energy. The resulting diffusion is then a weighted average over these jumps. As the temperature is lowered, the jump paths with higher activation energies become progressively ''frozen out.'' If the paths are connected in a parallel arrangement (in analogy to an electrical circuit) the averaged effective activation energy decreases as the temperature is reduced. (2) Experimental results were obtained using polycrystalline samples containing a spectrum of different types of grain boundaries. The overall observed diffusion is, therefore, a weighted average over these boundaries. As the temperature is lowered, the boundaries with the higher activation energies become progressively frozen out and the averaged effective activation energy decreases. (GHT)
- Research Organization:
- IBM Watson Research Center, Yorktown Heights, NY (USA); Cornell Univ., Ithaca, NY (USA). Dept. of Materials Science and Engineering
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- EY-76-S-02-2679
- OSTI ID:
- 6700761
- Report Number(s):
- COO-2679-22; TRN: 78-017265
- Country of Publication:
- United States
- Language:
- English
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