Atomic simulation on deformation and fracture of nano-single crystal of nickel in tension

Abstract

In order to elucidate the mechanism of deformation and fracture of microcomponents, numerical simulations are conducted for nanoscopic wire and film of nickel without lattice defects using molecular dynamics on the basis of the EAM (embedded atom method) potential. Applying a periodic boundary, large as well as small materials are subjected to a tensile strain along the [001] direction of the FCC (face-centered cubic) lattice. Here, the traverse stresses, σxx and σyy, in the former are kept at zero during the tension. The yield is brought about by the crystallographic slips on the (111) planes and there is little difference in the yield stresses among the wire, film and bulk. The slips continue to take place on multiple (111) planes and the plastic deformation leads to ductile fracture. Then, the displacement in the traverse direction on the cell boundaries of bulk is fixed in order to investigate the effect of constraint. It shows brittle fracture due to cleavage cracking. This implies that the constraint, which maybe introduced by local inhomogeneity of the material, brings about early crack nucleation and reduces the ductility of materials without lattice imperfection.