Orientation-dependent ductility and deformation mechanisms in body-centered cubic molybdenum nanocrystals

The knowledge regarding anisotropic mechanical behaviors in nanoscale body-centered cubic (bcc) met-als remains obscure. Herein, we report the orientation-dependent ductility in bcc Mo nanocrystals (NCs), which exhibit poor ductility along [110] direction but possess relatively better ductility along the [001] and [112] orientations. The origin of different deformability can be traced down to the distinct defor-mation mechanisms: the unexpected crack nucleation and propagation induce premature fractures in [110]-oriented NCs; in contrast, deformation twinning could contribute to the enhanced ductility in [001]-oriented NCs; interestingly, we find the activation of multiple dislocation slips in [112]-oriented NCs with the highest ductility. Further molecular dynamics simulations provide deeper insights into the defect dy-namics that are closely interlinked with experimental observations. Our findings advance the basic un-derstanding of orientation-dependent mechanical properties and help to guide endeavors to architecture the microstructures of bcc metals with enhanced ductility.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This study reports the anisotropic mechanical behaviors in nanoscale body-centered cubic (bcc) metals. It is found that bcc molybdenum nanocrystals exhibit poor ductility along the [110] direction but possess relatively better ductility along the [001] and [112] orientations. The deformation mechanisms, including crack nucleation and propagation, deformation twinning, and activation of multiple dislocation slips, are responsible for the different ductility in different orientations. Molecular dynamics simulations provide insights into the defect dynamics that correlate with experimental observations. These findings advance the understanding of orientation-dependent mechanical properties and guide the design of bcc metals with enhanced ductility.