It was recalled that the small size of the Cr atom, and its apparent ability to act as an interstitial, had led to speculation that Cr could appreciably affect irradiation damage recovery in Zr alloys. Previous work, which had indicated normal diffusion behavior for Cr in -Zr, had helped to form the view that diffusion in the latter was intrinsically normal. Here, an investigation was made in order to extend some earlier work on monocrystals, and to measure Cr diffusion parallel to, and perpendicular to, the c-axis. It was found that the Cr diffusion coefficients in -Zr monocrystals exhibited good Arrhenius behavior at temperatures of between 885 and 1120K. The diffusivities (table 174), their anisotropy (D|| > D), and their low activation energies, were consistent with the operation of a predominantly interstitial diffusion mechanism. The diffusion of Cr in the alloys was slower than in Zr.

G.M.Hood, R.J.Schultz: Journal of Nuclear Materials, 1993, 200[1], 141-3

Table 174

Diffusivity of Cr in Zr and Zr-Based Alloys