Diffusion of Interstitial Solute -- Vacancy Pairs in a Dilute Fcc Alloy

Download or read book Diffusion of Interstitial Solute -- Vacancy Pairs in a Dilute Fcc Alloy written by J. Wesley Miller and published by . This book was released on 1969 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has been proposed that the diffusion of cadmium in lead, which is inconsistent with the vacancy mechanism of solute diffusion, occurs by means of an interstitial migration which is strongly correlated due to an attraction between interstitial cadmium ions and vacancies. It is plausible that cadmium, like the noble metal solutes, should dissolve in lead by the dissociative mechanism, but interact strongly with vacancies by a screened electrostatic interaction. A thermodynamic model of a dilute dissociative solid solution is developed, and expressions for the equilibrium fractions of substitutional, interstitial and interstitial solute - vacancy close pair solute states are derived. Following the method of Lidiard, the solute diffusivity and linear enhancement of self-diffusion in this dissociative fcc alloy are calculated. It is also shown that the solute correlation factor, and therefore the isotope effect for solute diffusion, must be very small for this mechanism of diffusion. (Author).