Diffusion in Dislocations

Abstract

Diffusion in dislocation is a short-circuit diffusion often referred to as pipe diffusion. Diffusion usually is several orders of magnitude faster than in the lattice. Diffusion in dislocations depends on the density of the dislocations in the materials being studied. Every material, single-crystal or polycrystalline, contains dislocations, as isolated dislocations and also as aligned dislocations (found at sub-boundaries, commonly known as ‘low’ or ‘small-angle boundaries’). Since the contribution of dislocations to overall diffusion depends on density of the dislocations in the material, much experimental work was directed to the study of methods of artificially increasing the amounts of dislocations in various materials. The fast transport occurring in dislocations is not necessarily a desired property, since enhanced transport may cause undesirable consequences, e.g., creep in materials (while attempts are usually made to eliminate or reduce creep to acceptable levels). Creep is associated with edge-dislocation climb, which is diffusion controlled. Self and solute (impurity) diffusion is the subject of this chapter, and relevant equations are indicated. The analysis follows the Le Claire and Rabinovitch (J Phys C Solid State Phys 14:3863, 1981) approach to the problem of diffusion in dislocations.