The diffusion anisotropy of point defects in face-centered cubic and body-centered cubic metals in the presence of an applied bi-axial stress was studied. The diffusion anisotropy depended sensitively upon both the crystalline structure and the crystallographic direction in which the stress was applied. Thus, interstitials in face-centered cubic metals diffused faster in the plane of the compressive stress, than normal to it, when the stress was applied to the (001) plane. They diffused slower in-plane than out-of-plane when the stress was applied in the (111) plane. On the other hand, an applied bi-axial stress in the (001) plane of a body-centered cubic metal did not cause diffusion anisotropy. The results could be explained by considering the interaction of the defects, in their saddle-point configuration, with the external field; together with the constraints imposed by the crystal structure upon the defect jump-directions. The calculations showed that the diffusion anisotropy could be large and lead to unexpected results in practical situations.

Anisotropic Diffusion of Point Defects in Metals Under a Biaxial Stress Field Simulation and Theory. W.L.Chan, R.S.Averback, Y.Ashkenazy: Journal of Applied Physics, 2008, 104[2], 023502