An elasticity-based model was developed for predicting how the diffusion coefficient varied under an applied compressive stress. The stress affected the activation energy for motion of an atom, as well as its jump distance. Because a cubic crystal was slightly distorted tetragonally by an uniaxial stress, the activation energy for motion and the jump distance, and hence the diffusion coefficient, became different in directions normal to, and parallel to, the stress axis. The activation energy for motion was calculated by using the Flynn dynamic model for diffusion. By using the elastic constants for Ni–Al alloys, and taking account of the effect of the hydrostatic component of the applied stress upon

the diffusion coefficient, the model predicted that the diffusion coefficient would decrease by about 6% under an applied stress of 150MPa.

Coarsening of γ' in Ni–Al Alloys Aged under Uniaxial Compression - II. Diffusion under Stress and Retardation of Coarsening Kinetics. A.J.Ardell, S.V.Prikhodko: Acta Materialia, 2003, 51[17], 5013-9