Models of slow intergranular void growth due to void surface and grain boundary self-diffusion
Intergranular void growth at elevated temperature is studied in cases for which the shape of the void is determined by void surface diffusion and growth occurs by diffusion from the void tip and along the grain boundary. Equations governing the void shape are linearized and this linearization should not lead to gross errors in light of the large differences in the reported values of diffusion coefficients. A similarity solution for void shape is derived, and assuming growth in a particular manner, the similarity shape is shown to be determined by the choice of a/sup 3/v/..cap omega..v* where a is the void half-length, v is the speed of propagation of the void tip, ..cap omega.. is the atomic volume, and v* is a temperature dependent material parameter. An iterative solution for void shape which depends on a/sup 3/v/..cap omega..v* is derived also. By assuming the grain boundary flux to be distributed in such a manner that the grains separate as rigid bodies, the similarity and iterative shapes are linked to the applied stress, and the resulting growth models compared with the limiting cases of equilibrium and crack-like growth. The comparison indicates that void growth can be represented by a two-part solution where either the linearized equilibrium or the similarity model applies for small a/sup 3/v/..cap omega..v*, and the crack-like model applies for larger a/sup 3/v/..cap omega..v*. An analysis is included of relaxation times associated with a variety of diffusion mechanisms which are useful in determining the dominant mechanisms of matter transport.
- Research Organization:
- Brown Univ., Providence, R.I. (USA). Div. of Engineering
- Sponsoring Organization:
- US Energy Research and Development Administration (ERDA)
- OSTI ID:
- 7157063
- Report Number(s):
- COO-3084/42
- Country of Publication:
- United States
- Language:
- English
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