Correlation between local structural order and ductility of glasses*

Bulk metallic glasses (BMGs) are amorphous metallic alloys with desirable material properties such as high yield strength and superior corrosion resistance compared to conventional crystalline alloys. However, their use as structural materials has been limited because of their brittle behavior, especially in tension. In this work, we identify atomic-scale structural signatures in undeformed metallic glasses that are able to predict their mechanical response to tension or pure shear tests. In particular, we employ molecular dynamics simulations to prepare different types of glasses using a range of cooling rates and interaction potentials, including highly polydisperse soft-repulsive spheres, binary Lennard-Jones spheres, atomic systems that interact via the Stillinger-Weber potential, and binary and ternary alloys described by the embedded atom method. We then perform quasi-static tension or pure shear tests on the glassy samples, and measure the shear stress and local structural order as a function of strain. For each model system, we find a strong correlation between the measure of local structural order in the undeformed sample and the mechanical response at finite strain.