It was recalled that, if the migration properties of irradiation-created vacancies and interstitials were different, their annihilation behaviours at various sinks could be biased. The resultant microstructural changes led to macroscopic deformation. In the case of hexagonal close-packed metals, anisotropic diffusion of the point defects was an intrinsic property that was related to the structure of the crystalline lattice. The diffusional anisotropy was changed when a stress was applied to the crystal. The intrinsic anisotropy produced irradiation growth, while the stress-induced change in diffusional anisotropy caused deformations which were proportional to the applied stress and contributed to irradiation-creep. Irradiation creep which was due to stress-induced changes in diffusional anisotropy had been extensively investigated in cubic metals but not in hexagonal close-packed metals. The elastodiffusion tensor for point defects in hexagonal close-packed metals was derived here and was used to calculate creep deformation due to dislocations. It was suggested to be possible that hydrostatic stresses caused shear deformation during creep.

The Effect of Stress on Point-Defect Diffusion in HCP Metals and Irradiation Creep. C.H.Woo, C.B.So: Philosophical Magazine A, 2000, 80[6], 1299-318