A SIMS investigation of tracer diffusivities in an amorphous Ni54Zr46 alloy

Diffusion measurements of Hf and Au tracers were performed in an amorphous Ni0.54Zr0.46 alloy, both in vacuum and under a high hydrostatic pressure. A strong structural relaxation effect is observed for both solutes leading to a decrease of the diffusivity with annealing time. The relaxation time is nearly the same in both cases. Using well relaxed samples, we found activation energies of (1.78±0.20) eV/at. and (1.65±0.15) eV/at. for Hf and Au, respectively and pre-exponential factors of 2.8 × 10−9 and 1.9 × 10−9 m2 s−1. The activation volumes amount to 8.2 Å3 and 8.1 Å3, representing 0.52 and 0.51 mean atomic volume. We discuss the implications of the present results with respect to the long debated question of diffusion mechanism(s) in amorphous alloys.