A hidden variable in shear transformation zone volume versus Poisson's ratio relation in metallic glasses

Herein, we elucidate a hidden variable in a shear transformation zone (STZ) volume (Omega) versus Poisson's ratio (nu) relation and clarify the correlation between STZ characteristics and the plasticity of metallic glasses (MGs). On the basis of cooperative shear model and atomic stress theories, we carefully formulate Omega as a function of molar volume (V-m) and nu. The twofold trend in Omega and nu is attributed to a relatively large variation of V-m as compared to that of nu as well as an inverse relation between V-m and nu. Indeed, the derived equation reveals that the number of atoms in an STZ instead of Omega is a microstructural characteristic which has a close relationship with plasticity since it reflects the preference of atomistic behaviors between cooperative shearing and the generation of volume strain fluctuation under stress. The results would deepen our understanding of the correlation between microscopic behaviors (STZ activation) and macroscopic properties (plasticity) in MGs and enable a quantitative approach in associating various STZ-related macroscopic behaviors with intrinsic properties of MGs. (C) 2017 Author(s).