Materials scientsts sat up and took notice this summer when two research groups independently announced they had concocted a new type of steel -- amorphous steel -- that has three times the strength of conventional steel.

	ORGANIZED, LEFT: In this figure, two different elements are arranged to form a crystalline lattice structure like that found in an ordinary metal. DISORGANIZED, RIGHT: In this simulated mixture a small amount of the large element yttrium prevents crystal formation and facilitates metallic glass production. Click photo for larger image.

This new material eventually might be used to build lighter cars, tall buildings and, because it resists corrosion and is nonmagnetic, submarine and surface ship hulls that are invisible to magnetic detection.

But while the groups at the University of Virginia and Oak Ridge National Laboratory proved their new steel formulas the old-fashioned way -- by melting and casting alloys -- a third, Pittsburgh-based group found the same formula without heating anything other than some computer circuitry.

This computational method, developed by a group led by Carnegie Mellon University physicist Michael Widom, potentially could be used to create and perfect additional amorphous metals and to develop other metallic alloys.

The method is described in an upcoming issue of the journal Physical Review B.

Though the computations can take a day to run on even the fastest computers, the method could help researchers winnow the possible combinations of elements being considered for new amorphous metals and predict which combinations are most likely to yield the material's desired structure.

Amorphous metals, also known as metallic glasses, differ from conventional metals because their atoms are arranged randomly, as they are in a liquid or in window glass. Normally, when molten metal cools to form a solid, the atoms naturally assume the ordered pattern of a crystal.

Half a century ago, scientists discovered that metallic glasses with unusual properties could be formed by rapidly cooling molten metal, locking the atoms in an unordered state before they had a chance to rearrange themselves into crystals. But this cooling had to be so rapid -- 1,000 degrees in a millisecond -- that only thin sheets of metallic glass could be made and only at high cost. Not surprisingly, applications have been limited.

More recently, however, scientists have found that alloys that contain just the right combination of elements can be cooled at much the same rate as regular metals and retain their glassy structure, Widom said. That has opened the possiblity that amorphous metals might be produced in bulk so they could be used in structural materials.

The key, Widom said, is to find elements that disrupt the crystallization process.

In the case of amorphous steel, that turned out to be a large atom, called yttrium. The other elements in this steel formula -- iron, boron, carbon, chromium and molybdenum -- favor crystal formation. But adding a small amount of yttrium, or one of the elements known as rare earths, destabilizes the crystal and preserves the glassy structure.

It's something that Widom and his colleagues, including physicist Yang Wang of the Pittsburgh Supercomputing Center, discovered in the past six months. In the meantime, experimental groups led by C.T. Liu of Oak Ridge and Joseph Poon of Virginia confirmed the importance of yttrium and rare earths on their own.

The computational method nevertheless has provided important theoretical understanding of the amorphous steels, said Poon, the principal investigator on a Defense Advanced Research Projects Agency amorphous metal grant that includes Widom's group.

Poon said the amorphous steel could revolutionize the steel industry and might be ready for commercial use in three to five years.

Despite its superior strength and corrosion resistance, the amorphous steel remains quite brittle, he said. Further development is necessary to add some "give" to the material, perhaps by incorporating composite materials or even limited amounts of crystal.

Widom's computational method could help in that effort, Poon said, though the speed of the computations remains a limiting factor.

Wang, of the Pittsburgh Supercomputing Center, said it now takes about a day to simulate the cooling of 100 atoms of an alloy. Larger simulations would produce more reliable results, he noted, but would take much longer; a 1,000-atom simulation might take more than a month, for instance, on existing computers.

Once the structure is determined, however, Wang has developed a computational method to rapidly predict the mechanical and magnetic properties of a metal.

In addition to amorphous steels, Widom is investigating amorphous aluminum. The computational method also is useful for studying other types of metal alloys and thus far has generated recipes for more than 1,700 metal structures, most of which have yet to be analyzed.