Molecular-dynamics study on crack growth behavior relevant to crystal nucleation in amorphous metal

In this paper, the internal structure-changes around the crack-tip and the pertinent crack growth behavior in an amorphous metal were studied by a molecular dynamics (MD) simulation. In order to perform a large scale calculation, the domain decomposition method was used for parallel calculation. The Finnis-Sinclair potential for alpha-iron was used to describe the interatomic potential. Computed results show that nano-scaled crystalline phase grows around the crack-tip. The distribution of deformation zones and deformation mechanism are significantly altered. While grains are relatively small, they are not deformed, and the most amorphous-crystal interfaces have a large strain for phase transition. The emission of dislocations from the near crack-tip is observed after the crystal phase covered the crack-tip surfaces. Although CTOD obtained from MD analysis agrees to Dugdale's model very well during the amorphous state, the crack opening behavior changes remarkably after the crystallization.