Mechanical properties of nanoporous gold subjected to tensile stresses in real-time, sub-microscopic scale
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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.
This work was sponsored by the NSF DMREF program under Grant Nos. #1623051 and #1533969. We acknowledge DOE BES Geosciences (DE-FG02-06ER15786) for developing the in situ TEM capability. Facilities were made available through Virginia Tech’s Institute for Critical Technology and Applied Science Nanoscale Characterization and Fabrication Laboratory (ICTAS-NCFL). We acknowledge Dr. Diana Farkas, Dr. William Reynolds, and Dr. Sean Corcoran for their expertise and insightful conversations. We also acknowledge the Virginia Tech National Center for Earth and Environmental Nanotechnology Infrastructure (NanoEarth), a member of the National Nanotechnology Coordinated Infrastructure (NNCI), supported by NSF (ECCS 1542100) for providing technical consultation.
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Conflict of interest
The authors are unaware of any conflicts of interest regarding the data and findings presented in this manuscript.
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