Diffusional Flow in Polycrystalline Materials

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Abstract
The thermodynamic theory of equilibrium under nonhydrostatic stress developed by Gibbs and Kamb is applied to obtain the general solution for stress‐directed diffusion in an elastically isotropic solid. It is shown that the form of the strain‐rate tensor is the same for lattice and grain‐boundary diffusion mechanisms and that the relation derived in the classic paper by Herring is a special case of the general theory. Diffusional creep acting by itself cannot lead to steady‐state flow; strain rates always decline at high strains.