New glassy material stronger and tougher than steel

[Kozmos]

(PhysOrg.com) -- 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.

"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 Cal Tech, one of the pioneers in the field of metallic glass fabrication.

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.

In earlier work, the Berkeley-Cal Tech collaboration fabricated a metallic glass, dubbed "DH3," in which the propagation of cracks was blocked by the introduction of a second, crystalline phase of the metal. This crystalline phase, which took the form of dendritic patterns permeating the amorphous structure of the glass, erected microstructural barriers to prevent an opened crack from spreading. In this new work, the collaboration has produced a pure glass material whose unique chemical composition acts to promote extensive plasticity through the formation of multiple shear bands before the bands turn into cracks.

"Our game now is to try and extend this approach of inducing extensive plasticity prior to fracture to other metallic glasses through changes in composition," Ritchie says. "The addition of the palladium provides our amorphous material with an unusual capacity for extensive plastic shielding ahead of an opening crack. This promotes a fracture toughness comparable to those of the toughest materials known. The rare combination of toughness and strength, or damage tolerance, extends beyond the benchmark ranges established by the toughest and strongest materials known."

The initial samples of the new metallic glass were microalloys of palladium with phosphorous, silicon and germanium that yielded glass rods approximately one millimeter in diameter. Adding silver to the mix enabled the Cal Tech researchers to expand the thickness of the glass rods to six millimeters. The size of the metallic glass is limited by the need to rapidly cool or "quench" the liquid metals for the final amorphous structure.

"The rule of thumb is that to make a metallic glass we need to have at least five elements so that when we quench the material, it doesn't know what crystal structure to form and defaults to amorphous," Ritchie says.

The new metallic glass was fabricated by co-author Demetriou at Cal Tech in the laboratory of co-author Johnson. Characterization and testing was done at Berkeley Lab by Ritchie's group.

"Traditionally strength and toughness have been mutually exclusive properties in materials, which makes these new metallic glasses so intellectually exciting," Ritchie says. "We're bucking the trend here and pushing the envelope of the damage tolerance that's accessible to a structural metal."

Provided by Lawrence Berkeley National Laboratory

http://www.physorg.com/news/2011-01-glass-tops-steel-strength-toughness.html

Sciency news like that make me wet. Hopefully soon we'll be able to shank people with glass instead of steel.

 

[SS-18 ICBM]

Hopefully soon we'll be able to shank people with glass instead of steel.

Can't we already do that now?

Sounds like it will be some time before they can mass-produce it.

 

[Smellincoffee]

Ah, did Dr. Nichols finally get that transparent aluminum formula into action?

 

[Kozmos]

Can't we already do that now?

Sure but it's not super-effective like this will be.

 

[JohnRM]

Ah, did Dr. Nichols finally get that transparent aluminum formula into action?

DAMMIT! I was SURE I'd be the only one to post that! S.O.B!

 

[uppi]

Sounds like it will be some time before they can mass-produce it.

It's way too expensive to be mass produced

 

[emzie]

Palladium is like 800 bucks an ounce. Sounds like it has applications in bullet resistant windows but not much more.

Of course, there's a chance that I'm not anticipating some future development and 100 years from now, historians will be looking at internet archives and see this comment and think, "what an idiot!"

 

[civ_king]

Palladium is like 800 bucks an ounce. Sounds like it has applications in bullet resistant windows but not much more.

Of course, there's a chance that I'm not anticipating some future development and 100 years from now, historians will be looking at internet archives and see this comment and think, "what an idiot!"

Asteroid mining could dramatically decrease platinum group metal costs

 

[Olleus]

Maybe, but not in the near future. I have trouble imagining this in the medium term future as well. Asteroids are a long way away and doing anything in space is difficult.

 

[AL_DA_GREAT]

How brittle is it? It might hold more weight but wouldn't it be more prone to cracking?

 

[Kozmos]

Palladium is like 800 bucks an ounce. Sounds like it has applications in bullet resistant windows but not much more.

Of course, there's a chance that I'm not anticipating some future development and 100 years from now, historians will be looking at internet archives and see this comment and think, "what an idiot!"

Japs have found ways too artificially produce it so if there is a demand (and given the potential it's possible) there will be supply.

 

[uppi]

How brittle is it? It might hold more weight but wouldn't it be more prone to cracking?

Not at all. That is the point of this new material:

"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."

Japs have found ways too artificially produce it so if there is a demand (and given the potential it's possible) there will be supply.

While it is possible to transmute elements in particle accelerators, this is hideously expensive. The only way this is ever going to be mass produced is if we can somehow cheaply mine extraterrestrial sources or if the lessons learned from this material can be used to create a material from different components with similar properties.

 

[Kozmos]

I dont think that was the way the did it, but I lost the article in my bookmark cleaning.

 

[uppi]

I dont think that was the way the did it, but I lost the article in my bookmark cleaning.

That's the only way to make real Palladium.

Any other way they might get an alloy that somehow behaves similar than elemental palladium, but that would be unlikely to behave in the same way in this metal glass.

 

[Perfection]

That's the only way to make real Palladium.

Not true. http://en.wikipedia.org/wiki/Synthesis_of_precious_metals#Palladium