Self and solute diffusion in zirconium

Abstract

The effects of cobalt additions on the diffusion rates of ⁹⁵Zr and ⁶⁰Co in b.c.c. zirconium have been measured for cobalt concentrations between 0·0 and 2·0 at. % at an annealing temperature of 933°c. The diffusion coefficient of ⁹⁵Zr is markedly increased between 0·4 and 2·0 at. % cobalt while that of ⁶⁰Co is slightly decreased. An analysis of the results in terms of the deduced correlation factor for the cobalt solute indicates that diffusion does not occur by a single vacancy mechanism alone. The results are compatible with a model in which both single vacancies and dislocations contribute to the diffusion process. The vacancy component for the zirconium self-diffusion, however, is very much larger than predicted from empirical relations. The dislocation component can be accounted for in terms of a dislocation density between 2 × 10⁵ and 2 × 10⁸ lines/cm².