Diffusion studies in the metallic glass Zr61 Ni39 by Auger electron spectroscopy

The diffusion coefficients (D) of Cu and Al in the metallic glass Zr₆₁Ni₃₉ were measured in the temperature range 551–621 K by using the Auger depth profiling technique. The D values for Cu were observed to be higher than the corresponding values for Al by about an order of magnitude in this temperature range. The faster diffusion of Cu was consistent with the observed dependence, in this amorphous alloy, of diffusivity on the atomic size of the diffusing species. The values of the activation energy for diffusion (Q), evaluated on the basis of the observed Arrhenius type temperature dependence of D, were found to be 1.33 ± 0.17 eV for Cu and 1.68 ± 0.13 eV for Al. The corresponding values of the pre-exponential factor (D₀) were 10^{−7.57 ± 1.46} m² s⁻¹ and 10^{−5.35 ± 1.15} m² s⁻¹ respectively. No significant effect of structural relaxation of the glass on diffusivity could be observed from measurements on specimens subjected to a relaxation heat treatment prior to diffusion annealing.