This article shows the differences of two-dimensional polycrystal of a material with a rectangular unit cell with lattice spacing b and b (1 + epsilon), subjected to a uniform external stress sigma. Consider a grain in which the lattice vector of length b (1+ epsilon) is parallel to sigma, embedded in a grain in which the lattice vector b (1+ epsilon) is transverse to sigma. If the embedded grain grows at the expense of its matrix, the source of the stress will do work, and therefore the presence of this stress will drive the growth of the embedded grain. The author estimates the rate of this process, and discuss an apparently anomalous consequence of this estimate. The process involved is distinct from that of diffusional creep, but, because the two are related, provides a summary of the theory of diffusional creep.
