SHEAR LOCALIZATION AND PERCOLATION OF STABLE STRUCTURE IN AMORPHOUS SOLIDS

Molecular dynamics simulations of uniaxial tension in a two-dimensional model of a metallic glass exhibit varying degrees of shear localization depending upon the process by which each of the materials was produced. The samples that were quenched most gradually show the largest degree of localization. In addition higher strain rates lead to increased localization in the most rapidly quenched samples, while the more gradually quenched samples show the reverse strain rate dependence. This transition in localization and strain rate dependence coincides with a structural transition in the material. Gradually quenched samples have a higher percentage of atoms in quasi-crystal-like local environments. The transition in the mechanical properties coincides with the percolation of this backbone of quasi-crystal-like material. Shear localization occurs in regions where material is altered from this more stable structure to a fully amorphous structure under the effect of plastic deformation.