Effects of Cold Rolling and Annealing Prior to Dealloying on the Microstructure of Nanoporous Gold

The properties of nanoporous gold (NPG) were known to be dependent on the microstructure of NPG. In this study, the effects of cold rolling and annealing of the original Ag_0.7Au_0.3 alloy on the microstructure of NPG produced by dealloying under free corrosion condition were investigated. Ag_0.7Au_0.3 alloy samples were cold-rolled to different strain levels/thickness reductions up to 98% and annealed at 900 °C for 3 h before dealloying. It was found that cold rolling and annealing of the original alloy can lead to reduced ligament and pore sizes of NPG. Moreover, post-deformation annealing of the original alloy was found to facilitate the formation of a homogeneous and continuous NPG structure. The minima of pore and ligament sizes (both being ~8 nm) with uniform distribution were obtained in the annealed sample with a thickness reduction of 60% for a dealloying time of 7 h. The present study indicated the significant effect of a pre-dealloying treatment of the original alloy (by plastic deformation and annealing) on the formation and optimization of the NPG microstructure produced by dealloying.