New glass tops steel in strength and toughness

Jan 10, 2011 by Lynn Yarris
This micrograph of a deformed notch in palladium-based metallic glass shows extensive plastic shielding of an initially sharp crack. The inset is a magnified view of a shear offset (arrow) developed during plastic sliding before the crack opened. Credit: Image courtesy of Ritchie and Demetriou

(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 fabrication and we believe we can use it to make 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."

These are glassy palladium rods, with diameters ranging from 3 to 6 mm. Credit: Caltech/Marios D. Demetriou

Co-authoring the 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.

A transmission electron micrograph shows the amorphous structure of glassy palladium. (The area shown is 10 nm x 10 nm.) Credit: Caltech/Marios D. Demetriou

"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."

Explore further: Neutron tomography technique reveals phase fractions of crystalline materials in 3-dimensions

Related Stories

Los Alamos pressure process makes pure zirconium glass

Jul 15, 2004

Zirconium may not be a girl's best friend, but by squeezing the metal with roughly the same pressure needed to make diamonds, scientists at the University of California's Los Alamos National Laboratory made a pure glass that ...

Metallic Glass Yields Secrets Under Pressure

Mar 16, 2010

(PhysOrg.com) -- Metallic glasses are emerging as potentially useful materials at the frontier of materials science research. They combine the advantages and avoid many of the problems of normal metals and ...

New approach to understanding cracks

Feb 03, 2006

Could engineers have known ahead of time exactly how much pressure the levees protecting New Orleans could withstand before giving way? Is it possible to predict when and under what conditions material wear and tear will ...

Recommended for you

Refocusing research into high-temperature superconductors

20 minutes ago

Below a specific transition temperature superconductors transmit electrical current nearly loss-free. For the best of the so-called high-temperature superconductors, this temperature lies around -180 °C – a temperature ...

MRI for a quantum simulation

5 hours ago

Magnetic resonance imaging (MRI), which is the medical application of nuclear magnetic resonance spectroscopy, is a powerful diagnostic tool. MRI works by resonantly exciting hydrogen atoms and measuring ...

50-foot-wide Muon g-2 electromagnet installed at Fermilab

5 hours ago

One year ago, the 50-foot-wide Muon g-2 electromagnet arrived at the U.S. Department of Energy's Fermi National Accelerator Laboratory in Illinois after traveling 3,200 miles over land and sea from Long Island, ...

User comments : 26

Adjust slider to filter visible comments by rank

Display comments: newest first

newsreader
not rated yet Jan 10, 2011
Silly question... Are these metallic glasses transparent?
Shootist
4 / 5 (8) Jan 10, 2011
Not silly, I was thinking, transparent aluminum, myself.

Star Trek will never die.
dtxx
5 / 5 (3) Jan 10, 2011
Silly question... Are these metallic glasses transparent?


Usually not.
jwalkeriii
5 / 5 (3) Jan 10, 2011
Just FYI - Palladium is over $700/oz. USD
fmfbrestel
5 / 5 (3) Jan 10, 2011
I did not know the answer to your question, but i do know how to use Google, and so i did a simple google search and found the following response in a physicsforum post:

"Metals reflect most of the light because they have free electrons. These electrons are shaken by the electric field of the the light which is an electromagnetic wave. Shaken electrons emit two waves. One in the direction of the incoming wave that is seen as the reflected wave and one similar in the same direction as the incoming wave which, added with it, give a zero amplitude wave."

Ah, the power of the interwebs.
Chef
3.7 / 5 (3) Jan 10, 2011
Not silly, I was thinking, transparent aluminum, myself.

Star Trek will never die.


LOL, you beat me to it. I was thinking the same thing as soon as I read the article.

@jwalkeriii Wasn't there recent news of Japan finding a way to produce Palladium artificially? Maybe a joint production could be worked out.
pauljpease
5 / 5 (5) Jan 10, 2011
My thesis work considered an analogy between metallic glass and DNA. It turns out that the structure of DNA has some of the same problems these researchers face. I was interested in the question, at what point does DNA stop deforming and basically crack? This is still an unsolved question. Unfortunately, most people who study DNA don't follow trends in materials science, so they tend to oversimplify DNA and treat it like an isotropic rod characterized by a few constant parameters. These models work well on average, but lose some important behavior, which is why these models don't produce correct behavior in certain situations (e.g. very short DNA segments). It's akin to engineers designing a bridge. They must think about large scale dynamics because long bridges bend, but they can't neglect the fact that on the small scale they can crack and buckle. Actually, some bridges are designed to crack, like during an earthquake, to relieve stress and prevent widespread collapse.
holoman
1 / 5 (2) Jan 10, 2011
Can you say rare earth element.

I am sure the Chinese are licking their chops as
they control 97% of the worlds rare materials.
Objectivist
4.9 / 5 (8) Jan 10, 2011
Can you say rare earth element.

I am sure the Chinese are licking their chops as
they control 97% of the worlds rare materials.
They control 97% of the worlds rare earth mineral production. There is a ridiculous difference between that and actually controlling 97% of all rare earth minerals. Ridiculous.
Tektrix
5 / 5 (2) Jan 10, 2011
Not silly, I was thinking, transparent aluminum, myself.

Star Trek will never die.


Transparent aluminum, in the form of aluminum oxide, has been around for millions of years, as evidenced by sapphires and rubies.
Moebius
2.7 / 5 (6) Jan 10, 2011
It's time to stop calling metals glass, the title of this article proves it. It is purposefully misleading or the writer is an idiot. Either call them metallic glass as the interviewee calls it or just metal.

And a Sapphire is no more transparent aluminum than rust is red steel.

Tangent2
1 / 5 (1) Jan 10, 2011
Not silly, I was thinking, transparent aluminum, myself.

Star Trek will never die.


LOL, you beat me to it. I was thinking the same thing as soon as I read the article.

@jwalkeriii Wasn't there recent news of Japan finding a way to produce Palladium artificially? Maybe a joint production could be worked out.


You are right that there was a discovery, but it was Japan that discovered it. The article is here about China's artificial Palladium:
physorg.com/news/2010-12-japan-nano-tech-team-palladium-like-alloy.html
mrwolfe
5 / 5 (7) Jan 10, 2011
@moebius

Just because the most common glass is that stuff in your window doesn't mean all glass has to be made of silicon oxide.

The term "glass" describes a solid with an amorphous crystaline structure, it can be made from lots of things including metals.
Skepticus
2.6 / 5 (5) Jan 11, 2011
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


Deliberate hypebole for the uninformed. This is metallic glass, not the stuff your see through beyond your steering wheels. Certainly this nose-bleed inducing pricey Paladium microalloys will have its use, but Star Trek fans looking for transparent aluminum will have to wait or look elsewhere.
Skepticus
2 / 5 (4) Jan 11, 2011
And by the way, the term "metallic glass" is totally wrong. By the term, it means glass that has metal's characteristic, i.e. deformable and machinable and conductor of electrcity. The proper term should have been "Glassy Metals", i.e. metal with the structure of glass.
damnfuct
not rated yet Jan 11, 2011
Amorphous alloy?
Moebius
1.8 / 5 (5) Jan 11, 2011
@moebius

Just because the most common glass is that stuff in your window doesn't mean all glass has to be made of silicon oxide.

The term "glass" describes a solid with an amorphous crystaline structure, it can be made from lots of things including metals.


No kidding. Glass is commonly known as the see through silicon stuff, not metal. To refer to metals as glass is wrong I don't care what the dictionary definition is. It should be called amorphous if it isn't common glass. And while the scientific usage is correct this is recent, the word glass was around long before we knew what amorphous was. In other words we got it wrong, (common) glass is amorphous, amorphous isn't necessarily glass. That's my opinion and I'm sticking with it (unless I'm wrong). I demand that all dictionary and Wikipedia definitions be changed immediately too.
Moebius
2 / 5 (4) Jan 11, 2011
And I agree with Skepticus, metallic glass is wrong too. Metallic means metal like.

If we made common glass crystalline with grains would we call it metal?
yoatmon
not rated yet Jan 11, 2011
@ Moebius:
Graphene is approx. 217 stronger than steel and harder than diamonds. The elementary constituent of graphene is carbon. Graphene is transparent but is neither glass nor metal.
fmfbrestel
1 / 5 (2) Jan 11, 2011
And by the way, the term "metallic glass" is totally wrong. By the term, it means glass that has metal's characteristic...


No, what you really meant was "'it seems to imply' glass that has metal's characteristic" The term has already been coined to mean exactly what it is. I am sorry they didnt consult you when deciding what to call their material when Caltech first created them.
fmfbrestel
1 / 5 (2) Jan 11, 2011
me·tal·lic   [muh-tal-ik]
–adjective
1.
of, pertaining to, or consisting of metal.
2.
of the nature of or suggesting metal, as in luster, resonance, or hardness: metallic green; a harsh metallic sound.

-- Random House

knock off the arrogant (and wrong) grammar checks. Metalic Glass is correct. Mostly because those who created the material decided to call it that (and they have naming rights). But also because the english language supports their use.
fmfbrestel
3 / 5 (4) Jan 11, 2011
Definitions matter. Language matters. Especially in science and engineering. I am among the first to jump down the throats of those who post articles here with misleading and incorrect language, but the use of Metallic Glass is simply correct here despite your aesthetic disagreements with it.
Skepticus
2 / 5 (4) Jan 11, 2011
I still disagree. According to english grammar, the adjective before the noun gives the composite meaning of the adjective (secondary focus) that contributes further info to the noun (primary focus).
So metallic glass is glass that has metal's properties (which is wrong in this discussion). Just like red shirt, black face, ...arrogant, sanctimonious pricks. There is plenty more. Tradition doesn't mean it is grammatically right.
Jaak
not rated yet Jan 12, 2011
yes but I have read material technologies books in Estonian that refer to English articles writing about the same metal structure but call it "metaglass"
TheGhostofOtto1923
1 / 5 (6) Jan 16, 2011
@jwalkeriii Wasn't there recent news of Japan finding a way to produce Palladium artificially? Maybe a joint production could be worked out.
This has me puzzled. How does one artificially produce an element except by transmutation or alchemy? Sounds rather expensive. Comments?
Dug
1 / 5 (1) Jan 17, 2011
Can you say rare earth element.

I am sure the Chinese are licking their chops as
they control 97% of the worlds rare materials.

They control 97% of the worlds rare earth mineral production. There is a ridiculous difference between that and actually controlling 97% of all rare earth minerals. Ridiculous.

No, we as a nation are ridiculous for not strategically supporting our rare earth mining companies that all went out of business under the GW Bush administration - when he let that strategically important business go to China. Another example of how Bush and our self-serving politicians/government made us more secure.