Diffusion in amorphous NiZrAl alloys

Tracer diffusion coefficients for large and small sized impurities were measured in the bulk metallic glass NixZryAlz for several compositions. Molecular beam deposition was employed to grow thin films and secondary ion mass spectrometry was used to determine the concentration-depth profiles of several tracers. A dependence of the atomic mobility of the tracer on its size was found, as observed in the binary NixZry amorphous alloy system. The presence of the Al reduces the diffusion coefficients in general, with a stronger decrease for the small sized tracer. The results support the existence of two different diffusion mechanisms proposed for amorphous metallic alloys.