Mechanical properties of nanoporous gold subjected to tensile stresses in real-time, sub-microscopic scale

Abstract

Ductile metals infiltrated with interconnected nanopores through selective dealloying gain useful properties but become macroscopically brittle due to flow localization. The mechanical behavior of nanoporous metals is dependent on a complex relationship between the deformation of the nanoporous foam structure and the deformation of the individual ligaments. Recent simulations and in situ experiments have revealed many insights into the deformation behavior of nanoporous metals, but it remains unclear how to engineer the structure to reduce flow localization. We perform transmission electron microscopy in situ tensile experiments on freestanding nanoporous gold films and observe the morphology evolution of both the interconnected structure and individual ligaments during deformation. Most ligaments fractured through plastic instability after large plastic elongation. We also observed several unexpected results such as instances of strain hardening and nanoscale brittle fracture in individual ligaments. Our observations suggest that highly curved ligaments and a wider distribution of ligament diameters could each contribute to ductility and fracture toughness.