|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Mechanical Behavior of Nanostructured Materials
||L-166: Stress-driven Microstructural Evolution and Grain Boundary Doping in Nanocrystalline Alloys: A Direct Link Revealed by Quantitative In Situ Electron Microscopy
||Mo-Rigen He, Gyuseok Kim, Saritha Samudrala, Peter Felfer, Andrew Breen, Julie Cairney, Daniel Gianola
|On-Site Speaker (Planned)
The large fraction of material residing at grain boundaries (GBs) in nanocrystalline (NC) metals and alloys is responsible for their ultrahigh strength, but also undesirable microstructural instability under thermal and mechanical loads. However, the underlying mechanism of stress-driven microstructural evolution in a real NC microstructure is still poorly understood and precludes rational alloy design. Here we combine quantitative in situ electron microscopy with three-dimensional atom probe tomography to directly link the mechanics and kinetics of GB migration in NC Al films with the GB excess of O atoms. Site-specific nanoindentation leads to grain growth that is retarded by impurities, and enables quantification of the critical stress for the onset of GB migration. Our results show that a critical excess of impurities is required to stabilize interfaces in NC materials against mechanical driving forces, providing a new avenue for controlling deformation mechanisms and tailoring mechanical properties apart from grain size alone.
||Planned: Supplemental Proceedings volume