Tuesday, October 16, 2007

University of Virginia Research & Liquidmetal

Process creates lighter, stronger, nonmagnetic steel

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Portland, Ore. - In the world of materials, plastics have promised
to be the wave of the future since their invention, but don't count
metals out yet. By doping some ferrous base alloys with large rare-
earth or yttrium atoms, researchers have been able to prevent
crystallization, enabling "amorphous" (noncrystalline) steel that is
three times stronger than regular steel, one-third the weight and
nonmagnetic to boot. The research was sponsored by DARPA,
the Defense Advanced Research Projects Agency under the
auspices of Dr. Leo Christodoulou and the SAMS program
Structural Amorphous Metals Program.

In their liquid state, metals are amorphous because their atoms
are not ordered in a crystalline structure. When a metal slowly
cools into the solid state, all the atoms line up in a repetitive
pattern, enabling magnetism to get a grip.

In contrast, amorphous materials have atoms that are oriented
randomly, making them nonmagnetic. That is the structure of
the metal called Darva-Glass 101. Darva-Glass 101 is predated
by Darva-Glass 1, invented in 2002 at the University of Virginia,
which contains iron, chromium, manganese, molybdenum, carbon
and boron.

"To make Darva-Glass 101 we added a small amount of rare-
earth element or yttrium to Darva-Glass 1. The large size of the
added atom exerts enough atomic-level stress to destabilize
crystallization and form instead an amorphous structure," said
physics professor Joseph Poon. Poon and University of Virginia
colleagues Gary Shiflet, professor of materials science and
engineering, and materials physicist Vijayabarathi Ponnambalam
developed the new material.

Separately, a government research group at Tennessee's Oak
Ridge National Laboratory, led by Chain Liu, a materials scientist,
reported adding a large-atom yttrium to Darva-1 to achieve a
similar amorphous steel that also shows promise.

Both groups also report that the amorphous structure makes it
more difficult for surface oxidation (rust) to corrode the metal.
With all its superior features, however, the material is brittle,
and it could be as many as five years before that problem is solved
and commercial use can be made of the metal. The University of
Virginia scientists have given an exclusive license for Darva-Glass
1 to Liquidmetal Technologies Inc. http://www.liquidmetal.com;
Rancho Santa Margarita, California.

Possible applications for Darva-Glass 101 include its use in auto-
mobiles and as lighter, more corrosion-free ship hulls. The material
may also find applications as a corrosion-resistant coating, for
delicate yet strong surgical instruments and lighter recreational
equipment such as tennis racquets, golf clubs and bicycles.

The novel microstructures of amorphous metals are not confined
by the limitations imposed by a crystalline lattice. Shiflet said
amorphous metals can be treated like normal steel in machines or
they can be manipulated like a plastic-squeezed, compressed,
flattened and shaped. Its easy formability makes it a prime material
for submarines, because its lack of a magnetic response foils the
sensors that often trigger mines to explode.

Because the material is stronger, it could also be machined into
very thin layers that could lighten armor that is nevertheless still
immune even to armor-piercing bullets. And for electronic devices,
the metal could be used not only for lighter cases but also for
internal structural supports that allow devices to be thinner overall.


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