Coupled effect of sample size and grain size in polycrystalline Al nanowires

The coupled effects of sample size and grain size and the plastic deformation mechanisms of polycrystalline Al nanowires were investigated by molecular dynamics. With the number of grains across the diameter increasing from one to four, the 5 nm grain size nanowires showed a “smaller is stronger” effect, the 10 nm grained nanowires did not show any significant size effect, while the 20 nm grained nanowires showed a “smaller is weaker” effect. Different size effects are induced by competition between surface-mediated and grain boundary-mediated deformations.