Diffusivities of Ni, Zr, Au, and Cu in amorphous Ni-Zr alloys

Abstract

The chemical interdiffusion coefficient was measured in an amorphous ${\mathrm{Ni}}_{33}$ ${\mathrm{Zr}}_{67}$ -${\mathrm{Ni}}_{61}$ ${\mathrm{Zr}}_{39}$ bilayer sample. With the use of an "inert" marker layer of Au at the interface, and the regular solution approximation, tracer diffusivities for the constituent elements of the alloy were determined. In addition, tracer diffusivities of Au in this alloy, and of Au and Cu in homogeneous ${\mathrm{Ni}}_{50}$ ${\mathrm{Zr}}_{50}$ amorphous alloys, were measured. The tracer diffusivities of Cu and Ni were much greater than those of Zr and Au suggesting that atomic radii strongly influence diffusion in this alloy. A preliminary value of ≅ 105 kJ/mol for the activation enthalpy of Ni diffusion was deduced. Similarities between diffusion in $a-\mathrm{NiZr}$ alloy and $\alpha -\mathrm{Zr}$ are discussed.