Dealloying of an Au-based amorphous alloy

The dealloying behaviour of Au42Cu29Ti8Si21 and Au44Cu31Ti4Si21 amorphous (wheel-side) and partially crystalline (air-side) ribbons was investigated using potentiostatic and galvanostatic etching. The resulting microstructures are: i) on the wheel-side homogeneous porosity with size from tens of nanometers to less than 1 μm in between Au crystals is largely found, ii) on the air-side the porosity occurs on two length-scales, submicrometer as on the opposite size and micrometer where crystals are removed. The importance of surface morphology in the formation of the microstructure is outlined. The role of diffusion and nucleation in the mechanism of surface gold enrichment is established.