Homogeneous void nucleation in the presence of supersaturated vacancies and interstitials

Abstract

Homogeneous void nucleation in metals containing arbitrary vacancies and interstitials has been reexamined, with corrections made to the original work by Katz and Wiedersich. The void size distributions derived previously missed an exponential modification function with void size as the exponent. As a result, void nucleation under a given vacancy supersaturation ratio is underestimated by orders of magnitude. The second improvement arises from the accuracy in calculating the vacancy arrival rate to a void. The present work proposes establishing a direct relationship between the vacancy arrival rate and the available self-diffusion coefficient. With these corrections and improvements, void nucleation in pure Fe is calculated as an example, and an analytic fitting formula is provided. The required vacancy supersaturation ratio and interstitial-to-vacancy flux ratio for void nucleation calculations can be easily obtained from an analytical solution of rate theory calculations, in which dislocation density and displacements per atom (dpa) rate are adjustable inputs. Alternatively, the nucleation rate calculation can be incorporated into rate theory calculations considering evolving dislocation densities, which leads to time-dependent void nucleation.