New Glass Tops Steel in Strength and Toughness

Glass stronger and tougher than steel? A new type of damage-tolerant metallic glass, demonstrating a strength and toughness beyond that of any known material, has been developed and tested by a collaboration of researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab)and the California Institute of Technology. What’s more, even better versions of this new glass may be on the way.

“These results mark the first use of a new strategy for metallic glass fabrication and we believe we can use it to make glass that will be even stronger and more tough,” says Robert Ritchie, a materials scientist who led the Berkeley contribution to the research.

The new metallic glass is a microalloy featuring palladium, a metal with a high “bulk-to-shear” stiffness ratio that counteracts the intrinsic brittleness of glassy materials.

Glassy materials have a non-crystalline, amorphous structure that make them inherently strong but invariably brittle. Whereas the crystalline structure of metals can provide microstructural obstacles (inclusions, grain boundaries, etc.,) that inhibit cracks from propagating, there’s nothing in the amorphous structure of a glass to stop crack propagation. The problem is especially acute in metallic glasses, where single shear bands can form and extend throughout the material leading to catastrophic failures at vanishingly small strains.

“Because of the high bulk-to-shear modulus ratio of palladium-containing material, the energy needed to form shear bands is much lower than the energy required to turn these shear bands into cracks,” Ritchie says. “The result is that glass undergoes extensive plasticity in response to stress, allowing it to bend rather than crack.”

Ritchie, who holds joint appointments with Berkeley Lab’s Materials Sciences Division and the University of California (UC) Berkeley’s Materials Science and Engineering Department, is one of the co-authors of a paper describing this research published in the journal Nature Materials under the title “A Damage-Tolerant Glass.”

Co-authoring the Nature Materials paper were Marios Demetriou (who actually made the new glass), Maximilien Launey, Glenn Garrett, Joseph Schramm, Douglas Hofmann and William Johnson of Caltech, one of the pioneers in the field of metallic glass fabrication.