Effects of notches on the deformation behavior of submicron sized metallic glasses: Insights from in situ experiments

Abstract

Reducing the size of metallic glasses (MG) to submicron or nanoscale levels improves their strength and ductility. However, there is no clear consensus in the literature regarding their mechanical behavior in the presence of a flaw or notch. In this work, quantitative tensile tests on notched submicron sized CuZr MG specimens were conducted inside a transmission electron microscope to study their deformation characteristics. Strength was found to be notch insensitive for shallow notched thick specimens, although reducing specimen dimensions and increasing notch sharpness enhances it by 14%. It was reasoned that the severity with which shear bands are geometrically constrained determines the strength and fracture morphology of notched specimens. Softening, accompanied with a transition to necking failure, occurs when the width of ligament that connects the notches is smaller than 80 nm. The competition between shear band propagation and plastic zone growth-mediated homogeneous activation of shear transformation zones was found to be responsible for this brittle to ductile transition. Current results provide unique insights into the various design aspects to be considered for reliable engineering of small scale components.