Solid-state amorphization, interdiffusion, and ion-beam mixing in Au/Zr and Ni/Zr

Abstract

Inert-gas markers, Rutherford backscattering, and x-ray diffraction were used to investigate solid-state interdiffusion in Ni/Zr and Au/Zr bilayer films as a function of temperature; microstructural studies during annealing were performed in situ, in a high-voltage electron microscope. Au, in contrast to Ni, is not an anomalously fast diffuser in crystalline Zr. Nevertheless, an amorphous product phase was found in both alloy systems for reaction temperatures  550 K; heterogeneous nucleation of the amorphous phase was observed in Au/Zr. The interdiffusion data reveal two distinct Arrhenius regimes, 330–∼470 K and ∼480–550 K, with quite different apparent activation enthalpies. These thermal interdiffusion results are compared with temperature dependent studies of ion-beam mixing in similar bilayer specimens. This comparison indicates that the enhanced efficiencies observed for ion-beam mixing above ∼480 K result from the as-prepared metastable microstructurc, and are not due to radiation-enhanced diffusion.