Self-diffusion along Stationary and Moving Grain Boundaries in a-Hf

Abstract

Grain boundary (GB) self-diffusion of Hf has been studied in the α(HCP) phase of Hf-3 wt.% Zr in the temperature range 910 to 1493 K using the radiotracer serial sectioning technique. As it was not possible to fully stabilize the grain size in the material by any pre-diffusion heat treatment, part of the GBs could move during the diffusion anneals due to a continuous grain growth. As a consequence, the measured penetration profiles had a rather untypical shape and could not be treated in terms of the standard GB-diffusion models which consider only stationary GBs. We have developed a comprehensive procedure for processing such profiles based on a simple model of tracer diffusion in a polycrystal containing both stationary and moving GBs