Herein, the effect of sputtering rate on the fraction of special grain boundaries in 5xxx series Al–Mg alloys is explored. Samples are synthesized via interrupted direct current (DC) magnetron sputtering with varying deposition rates, and the grain size and grain boundary character are evaluated with electron backscatter diffraction (EBSD). The highest sputtering rate (7 nm s−1) leads to an increase in the total number of special grain boundaries, ≈1.5× greater than that of the lower rates. Increased thermal energy and enhanced stress relaxation during film growth promote the formation of Σ3 and Σ7 boundaries.

The role of interfaces and the controlling synthesis parameters of graded dealloyed nanoporous metallic materials are investigated, focusing on the dealloying front progression in complex precursor materials with multiple alloy compositions. Specifically, the effects of relative density and chemical potential on the dealloying front in sputtered bilayer copper alloy films are explored with two case studies: Cu–Al/Cu–Al and Cu–Al/Cu–Zn. Cross-sectional scanning electron (SEM) micrographs and energy-dispersive X-ray spectroscopy mapping trace the dealloying front across three time intervals, while top-surface and cross-sectional SEM probes the final dealloyed foam morphology. Final ligament sizes were found to be independent of the synthesis parameters (21–28 nm), due to a combination of fast reaction times and phosphate-inhibited surface diffusion of Cu atoms. The chemical potential gradient yielded faster reaction times, whereas slower reaction times and a higher at.% of Cu in the top layer of precursor material produced a more uniform morphology. Graphical abstract