Some correlations for diffusion in amorphous alloys

Diffusion of several impurity atoms (Cu, Al, Au, and Sb) has been studied in Zr₆₁Ni₃₉ and Fe₈₂B₁₈ amorphous alloys. A definite correlation between the diffusion coefficient (D) and the atomic size of the diffusant is seen for the metal-metal (M–M) alloy, while it is not clear for the metal-metalloid (M–Me) alloy. Based on the present data, as well as other published data in binary amorphous alloys, empirical correlations have been found between (i) the activation energy (Q) and the energy required to form a hole of the size of the diffusing atom in the host alloy, and (ii) the pre-exponential factor (D₀) and Q. While the former correlation is seen only for binary M–M type of amorphous alloys, the latter correlation is more general and holds for all types of amorphous alloys. Based on the correlation between D₀ and Q, it is proposed that there are two distinct mechanisms of diffusion in amorphous alloys.