The hardening and softening mechanism governed by GB stability in nanograined metals: A molecular dynamics study

The failure of Hall-Petch effect shows that the strengthening of nanograined metals is not only affected by size but also by grain boundary (GB) stability. In this work, the effect of GB stability on the properties of Cu-Ni nanocrystalline alloy was investigated by molecular dynamics simulations. The deformation mechanisms of nanocrystalline Cu-Ni (e.g. GB sliding, the generation of deformation twinning and dislocation reactions) are discussed in detail. It was found that the more stable GB means the higher GB energy barrier and the more force to hind atomic slip in the GB. The material is strongest when the homogeneous segregation degree of nanograined metals was about 0.9. By molecular dynamics simulation, the segregation is studied omni-directionally and deeply from the point of view of dislocation binding GB energy for the first time.