Effects of atomic scale fluctuations and notches on the plastic deformation and failure of metallic glasses
Yong-Wei Zhang (IHCP Singapore), Zhendong Sha (Institute of High Performance Computing, A*Star, Singapore), Murali Palla (), R. Narasimhan (Department of Mechanical Engineering, Indian Institute of Science, Bangalore ), Huajian Gao (Brown University)
Plasticity at Different Length Scales
Mon 10:45 - 12:15
CIT 219
Metallic glasses exhibit a wide range of fracture toughness from 1 to 80 MPa.m1/2 and even higher, and currently, their underlying deformation and failure mechanisms are highly debated. Here we conduct large-scale molecular dynamics simulations to study the plastic deformation and fracture behavior of three metallic glass systems, that is, FeP, MgAl and CuZr. We show that brittle fracture in the FeP glass is governed by an intrinsic cavitation mechanism near crack tips in contrast to extensive shear banding in the ductile CuZr glass. Our simulations also reveal that the spatial correlation functions of atomic scale fluctuations of plastic displacements in three metallic glass systems of FeP, MgAl and CuZr, follow an exponential law with a characteristic length scale that governs the shear band thickness and fracture mode in these materials. These findings corroborate very well with the existing experimental observations and suggest the characteristic length is a fundamental size measure for the shear transformation zone size in metallic glasses. For the notched CuZr metallic glass, we find that the plastic deformation occurring at the notch root effectively blunts the stress concentration at the root, leading to a notch-insensitive failure strength. The notch, however, dictates the failure location from which shear bands are nucleated. These results provide useful guidelines for the design, testing and engineering of metallic glasses.