Deformation analysis of amorphous metals based on atomic elastic stiffness coefficients

概要

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We have performed the indentation simulation to a Ni50Al50 amorphous metal by the molecular dynamics method, and discussed the plastic deformation behavior in amorphous structure by atomic strains and atomic elastic stiffness coefficients, Bαij, or the second-order derivatives of atomic energy. During the indentation, zonal regions like shear bands below the indentation point show large values of local deviatric strains and local volume strains.The number of both positive and negative switching of positivity of det Bαij increases according to the formation of shear bands. On the other hand, the "probabilistic" switching of positivity of det Bαij constantly occurs due to subtle changes in local volume strains even at the equilibrium state. In order to understand the plastic deformation behavior, we should observe the switching of positivity of det Bαij with the exception of small variation of local volume strains. Evaluation of the switching with a large variation of local volume strains reveals occurrence of deformation propagation and extensive rearrangements of atoms around shear bands.