Characterization of nanometer-scale defects in metallic glasses by quantitative high-resolution transmission electron microscopy

Abstract

Although defects can have a significant effect on the properties of amorphous materials, in many cases these defects are poorly characterized and understood. This is at least partly due to the difficulty of imaging defects in amorphous materials in the electron microscope. In this work, we demonstrate the utility of quantitative analysis of high-resolution transmission electron microscopy for the identification and characterization of nanometer-scale defects in metallic glasses. For a proper identification of such defects, it is important to carefully consider the effects of the imaging conditions and thickness variations in the sample, both of which we describe in detail. As an example, we show that regions of localized plastic deformation (shear bands) in bulk metallic glasses contain a high concentration of nanometer-scale voids. These voids apparently result from the coalescence of excess free volume once the applied stress is removed.