Large-grained specimens of the body-centered cubic alloy were studied at temperatures ranging from 620 to 1173K (Hf) or at temperatures ranging from 920 to 1167K (Nb). The Hf diffusion profiles were determined by means of secondary ion mass spectrometry, and the Nb profiles were determined by using microtoming and radio-tracer techniques. The Hf data exhibited a smooth temperature-dependent behavior across the monotectoid temperature (875K) and could be described by:

D(m2/s) =  10-9exp[-1.4(eV)/kT]

The diffusivity of Nb tended to be lower than the corresponding value for Hf. Overall, all of the data were characteristic of diffusion in body-centered cubic Zr. The effect of an oxide film at low temperatures was avoided by using ion-implanted Hf diffusion sources.

H.Zou, G.M.Hood, R.J.Schultz, N.Matsuura, J.A.Roy: Journal of Nuclear Materials, 1996, 230[1], 36-40