Deformation analysis of amorphous metals based on atomic elastic stiffness coefficients

摘要

The elastic limit of a crystal can be evaluated by the positiveness of elastic stiffness coefficients, B-ijkl. We had demonstrated that the nucleation of lattice defects such as dislocation and cleavage cracking can be predicted by the atomic B-ijkl at each atom point. Amorphous metals and bulk metallic glasses draw intense interest whether the criteria are applicable or not since they are regarded as the ultimate of lattice defects. In the present study, an amorphous Ni-Al binary alloy is made by a usual melt - quench simulation and subjected to tension by means of molecular dynamics simulation. During simulations, the positiveness of atomic B-ijkl is discussed for all atoms. Contrary to an Ni-Al crystal, many atoms show negative value even in the initial equilibrium of the amorphous before loading. These unstable atoms turn out to be the non-clustered atom or the outer-shell of the local cluster such as 12(0,0,12,0) icosahedron. On the other hand, the centre atoms of the local clusters show high stability resulting in the positive B-ijkl of the whole system. It is also demonstrated that the change in the atomic B-ijkl can reveal the collapse and re-configuration of local clusters during the deformation.