Mechanistic understanding of enhanced thermal stability of twinned copper nanowires

Abstract

Thermal instability problems of nanostructured materials, including grain coarsening and recrystallization, can be alleviated by introducing nanoscale coherent twin boundary (CTB) structures. However, the detailed interaction mechanism between CTB and grain boundaries (GBs) during microstructural transformation has not been well elucidated. To gain insight, we investigate the migration behavior of CTB-intercepted GBs in twinned copper nanowires at elevated temperatures through transmission electron microscopic observations and molecular dynamics simulations. The results show that numerous partial dislocations are conveyed to the CTB-intercepted GB through the densely distributed CTBs and further transferred to the nanowire surface along the GB. The growth of the twinned region along the diminishing GB is driven by minimizing the excess energy stored in dislocation defects and GBs. This CTB-mediated GB migration in twinned copper nanowires can be deactivated by surface passivation. This study will help to elucidate how the thermal stability of nanostructured metals is influenced by the twin structure and surface passivation.