Accession Number : AD0691382

Title :   DIFFUSION OF INTERSTITIAL SOLUTE -- VACANCY PAIRS IN A DILUTE FCC ALLOY.

Descriptive Note : Technical rept.,

Corporate Author : HARVARD UNIV CAMBRIDGE MASS DIV OF ENGINEERING AND APPLIED PHYSICS

Personal Author(s) : Miller,J. Wesley

Report Date : APR 1969

Pagination or Media Count : 30

Abstract : 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)

Descriptors :   (*CADMIUM, TRANSPORT PROPERTIES), (*CRYSTAL DEFECTS, LEAD ALLOYS), SOLID SOLUTIONS, THERMODYNAMICS, DIFFUSION, CADMIUM ALLOYS

Subject Categories : Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE