Critical-temperature/Peierls-stress dependent size effects in body centered cubic nanopillars

The size-dependent plasticity of body centered cubic (bcc) metals is different from face centered cubic (fcc) metals: the size-effect exponent n varies for different bcc metal nanopillars (n = 0.8–1.0 for V, Nb; n = 0.3–0.5 for Ta, Mo, W). This inconsistency is first explained through a simple model based on the temperature-dependent Peierls stress. The bcc V nanopillars with a low critical temperature and Peierls stress showed a fcc-like size effect with n = 0.79, and our in-situ TEM compression study revealed that fcc-like dislocation starvation occurred in bcc V nanopillars, indicating that a small Peierls stress in V contributes to the fcc-like behavior.