Molecular dynamics simulation study of the effect of grain size on the deformation behavior of nanocrystalline body-centered cubic iron

A molecular dynamics simulation study has been carried out to clarify the effect of grain size on the deformation behavior of nanocrystalline body-centered cubic Fe. Average flow stresses were found to decrease with grain refinement below 14.7 nm, exhibiting a breakdown in the Hall–Petch relation. A change in the dominant deformation mechanism from dislocation glide to grain boundary sliding appeared to be the direct cause of the breakdown in the Hall–Petch relation observed in the present nanocrystalline pure Fe.