MADISON Drawing on powerful computational tools and a state-of-the-art scanning transmission electron microscope, a team of University of Wisconsin-Madison and Iowa State University materials science and engineering researchers has discovered a new nanometer-scale atomic structure in solid metallic materials known as metallic glasses.
Published May 11 in the journal Physical Review Letters, the findings fill a gap in researchers' understanding of this atomic structure. This understanding ultimately could help manufacturers fine-tune such properties of metallic glasses as ductility, the ability to change shape under force without breaking, and formability, the ability to form a glass without crystalizing.
Glasses include all solid materials that have a non-crystalline atomic structure: They lack a regular geometric arrangement of atoms over long distances. "The fundamental nature of a glass structure is that the organization of the atoms is disorderedjumbled up like differently sized marbles in a jar, rather than eggs in an egg carton," says Paul Voyles, a UW-Madison associate professor of materials science and engineering and principal investigator on the research.
Researchers widely believe that atoms in metallic glasses are arranged only as pentagons in an order known as five-fold rotational symmetry. However, in studies of a zirconium-copper-aluminum metallic glass, Voyles' team found there are clusters of squares and hexagonsin addition to clusters of pentagons, some of which form chainsall located within the space of just a few nanometers. "One or two nanometers is a group of about 50 atomsand it's how those 50 atoms are arranged with respect to one another that's the new and interesting part," he says.
Measuring the atomic structure of glass at this scale has been extremely difficult. Researchers know that, at a few tenths of a nanometer, atoms in metallic glasses have the same distances between them as they
|Contact: Paul Voyles|
University of Wisconsin-Madison