Correlation between local elastic heterogeneities and overall elastic properties in metallic glasses

Abstract The common notion suggests that metallic glasses (MGs) are a homogeneous solid at the macroscopic scale; however, recent experiments and simulations indicate that MGs contain nano-scale elastic heterogeneities. Despite the fundamental importance of these findings, a quantitative understanding is still lacking for the local elastic heterogeneities intrinsic to MGs. On the basis of Eshelby's theory, here we develop a micromechanical model that correlates the properties of the local elastic heterogeneities, being very difficult to measure experimentally, to the measurable overall elastic properties of MGs, such as shear/bulk modulus and Poisson's ratio. Our theoretical modeling is verified by the experimental data obtained from various MGs annealed to different degrees. Particularly, we revealed that upon annealing, the Poisson's ratio decreases if shear softening dominates the behavior of local soft regions or increase if pressure softening becomes dominant in MGs. Our results provide quantitative insights into the structural mechanism of the Poisson's ratio criterion on the ductility long established for MGs. Finally, The correlation between the Poisson's ratio of a glass and the fragility of its corresponding liquid is also discussed.