Shape of intergranular creep cracks growing by surface diffusion

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.