Theory of Grain Boundary Diffusion

Abstract

The previously proposed dependence of the structure of grain boundaries upon the angle of disorientation of the two grains is used as a basis of a quantitative consideration of diffusion along grain boundaries and in particular of the apparent activation energies. At small angles in the dislocation range the diffusion is controlled by volume diffusion mechanism. At high angles near 45° the model of a uniform grain boundary is applicable. In the intermediate range an array of rod-like areas of distorted lattice leads to low or even negative apparent activation energies. The theory is in good agreement with experiment.