By Gary Thomas
A team of researchers from the Iowa State University and the University of Wisconsin-Madison has determined a novel nanoscale atomic structure in metallic glasses using advanced computational tools and a powerful scanning transmission electron microscope.
The study findings are helpful to better understand this atomic structure. Using this knowledge, manufacturers can adjust characteristics of metallic glasses such as ductility, the ability of changing shape under strain without breaking and formability, the capability of forming a glass without crystallization.
Paul Voyles, principal investigator of the study, informed that in a basic glass structure, atoms are arranged in a disordered fashion. A common belief among scientists is that the arrangement of atoms in metallic glasses is only in pentagon shapes. Conversely, Voyles' group discovered clusters of hexagons and squares together with clusters of pentagons within a space measuring a few nanometers in a zirconium-copper-aluminum metallic glass.
This nanoscale length of 1-3 nm comprises nearly 50 atoms and their arrangement with respect to each other is the new and fascinating part. Voyles’ group utilized an advanced scanning transmission electron microscope at the University of Wisconsin-Madison to analyze this nanoscale atomic structure. Voyles explained that the microscope can produce a 2-nm-dia electron probe beam, which enables the measurement of this nanoscale length.
The research team then combined the data of the microscopic analysis with powerful computational techniques to perform simulations that precisely reproduce the experiments.
The integration of these two techniques is helpful in hypothesizing general principles about nanoscale clustering and rotational symmetry, said Voyles. If the role of the structure in controlling the properties of metallic glasses and the participation of various elements in these novel structures are known, researchers can manipulate properties by varying the composition or changing the heating and cooling rate of a material to obtain a more useful structure.
The research team’s next step is to measure the properties of the metallic glass’ most realistic structural simulations to understand the relations between the structure and those properties.