Enhanced strengthening via nanoscale composition modulation

This work investigates the origins of strengthening in nanocrystalline Pt-Au thin films. Drawing from a previous high-throughput combinatorial survey of 784 candidate films, five distinct films were selected for detailed analysis. Microstructural characterization using transmission electron microscopy, energy-dispersive X-ray spectroscopy, x-ray diffraction, x-ray reflectivity, and automated crystal orientation mapping was used to quantify contributions from grain size, solute content, texture, density, and dislocation content. In addition to those sources, the highest hardness film benefited from nanoscale composition modulations, outperforming comparable Pt-Au alloys that lacked composition modulation. The modulations are akin to spinodal decomposition microstructures, though distinct in their formation mechanism. This work provides a forensic analysis of how subtle, nanoscale chemical features, identified through combinatorial exploration and subsequent detailed analysis, can influence the mechanical properties of alloy systems.