Medium-Range Order in Metallic Glasses Studied by Fluctuation Microscopy

Abstract

Atomic structure on the 1-2 nm scale, often referred to as “medium-range order” (MRO), is of great importance for understanding the properties of disordered materials. It is, however, difficult to adequately characterize medium-range order. Fluctuation microscopy is a newly developed TEM technique that has successfully been employed to characterize MRO in amorphous semiconductors. The predominance of highly directional covalent bonds leads naturally to the presence of MRO in amorphous semiconductors. For metallic glasses, however, the bonding is primarily metallic and nondirectional. Thus, it is not readily apparent whether MRO would exist, or whether fluctuation microscopy is a useful tool for studying the structure of metallic glasses. in this work we report the use of fluctuation microscopy to identify differing degrees of MRO in Zr-based bulk metallic glasses; the MRO depends on the alloy content and the method of TEM specimen preparation.