THE NONEQUILIBRIUM THERMODYNAMICS OF INTRACRYSTALLINE DIFFUSION UNDERNONHYDROSTATIC STRESS

Intracrystalline diffusion induced by non-hydrostatic stress is formul ated on the basis of the non-equilibrium thermodynamics of deformable solids. In the case of ideal solution, the chemical potential <(mu)ove r tilde> of the diffusing component a is expressed as <(mu)over tilde> (a) = -sigma(ij)nu(epsilon(ij)(a) + delta(ij)/3) + f(a), where nu is t he molar volume, sigma(ij) is the stress tensor, f is the molar Helmho ltz free energy, delta(ij) is the Kronecker delta, epsilon(ij) represe nts the strain tensor of the crystal lattice, and the superscript a de notes the partial molar values of component a. The driving force of in tracrystaline diffusion of component a is approximately -nu(partial de rivative epsilon(ij)/partial derivative C-a)del sigma(ij). The lattice diffusion creep is reinterpreted in terms of <(mu)over tilde>.