Monolayer oxide enhanced flow stress in nanoporous gold: the size dependence

• Main Authors: Peng Wu, Xing-Long Ye, Ling-Zhi Liu, Hai-Jun Jin
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2018-09-01
• Series: Materials Research Letters
• Subjects: Strength; flow stress; size-effect; surface-effect; nanoporous gold
• Online Access: http://dx.doi.org/10.1080/21663831.2018.1486337

Compression of nanoporous gold in situ under electrochemical control reveals that its flow stress can be enhanced by surface coverage of monolayer oxide. Here we present a study on the monolayer oxide induced changes in flow stress of an nanoporous gold, while the ligament size is varied by more than 2 orders of magnitude. The increase percentage of flow stress (of nanoporous gold and nano-ligaments) induced by surface monolayer oxide is negligible when the ligament size (L) exceeds ∼2 µm, increases with decreasing L for ∼200 nm < L < ∼2 µm, and then saturates at ∼27% for L < ∼200 nm. These results indicate a transition from bulk-like to surface-mediated deformation behavior of nano-ligaments as L decreases from ∼2 µm to ∼200 nm. Our observation at L < ∼200 nm support the notion that the deformation is dominated by the surface-dislocation-nucleation at this scale.