The pre-factor, D-0, of the diffusion coefficient in amorphous alloys and in grain boundaries

摘要

Self-diffusion in several amorphous alloys and in silver grain boundaries of different orientation are analyzed and compared with those of crystals with the aim of a better understanding of the diffusion mechanism operating in disordered structures. Several experimental observations are discussed, including the concentration depth profiles, the Arrhenius plots of the diffusion coefficients and the effective activation volume and isotope effect. As an important difference between the diffusion behavior of the amorphous alloys and general grain boundaries on the one side and of crystals on the other side a distinctly different correlation between the pre-factor, D-0, of the diffusion coefficients and the effective activation enthalpy is identified. This correlation is regarded as key information to determine the validity of different diffusion models proposed for disordered structures. It is shown that a detailed consideration of the structural disorder and the related distribution of energy states of the migrating atoms is necessary in order to understand the diffusion in disordered structures. (C) 1998 Elsevier Science B.V. [References: 68]