Much more is coming. Artificial hips and knees, ultralight cases for phones, PDAs, and laptops, and nondulling surgical blades are all in development. The material is costly, but companies can recoup some expenses because it shrinks far less than conventional metals as it solidifies, which means little or no postforming processing is needed. Amorphous scalpels, for example, pop from their molds already sharp, whereas conventional scalpels require an additional sharpening step. And amorphous blades stay sharp, says Johnson with a smile. “A guy from one of the big razor blade companies keeps calling me, but I haven’t had time to return his calls. Frankly, I don’t think they want amorphous razor blades—they would stay sharp for a year.”
On the military front, the Army is testing an armor-piercing bullet called a kinetic energy penetrator for use by ground-attack jets and armored vehicles, while the Navy evaluates lightweight amorphous-alloy fragmentation bombs. But price remains a barrier. “Right now, it would appear that the cost of these materials will be fairly high and not competitive,” says Robert Dowding, a materials engineer at the Army Research Laboratory at the Army’s Aberdeen Proving Ground in Maryland. He says a chief reason amorphous metals are expensive is that their constituent metals need to be pure: “A small amount of oxygen or carbon in the mix can cause crystallization” and ruin the alloy.
But other researchers are making progress here as well. “Adding certain rare earth elements to the mix attracts impurities,” says John Perepezko, a materials science and engineering professor at the University of Wisconsin at Madison. Such elements allow the use of commercial-grade metals in amorphous alloys, which can dramatically lower costs.
As long as amorphous alloys such as Liquidmetal2 cost $15 a pound, they will remain “boutique metals,” says Johnson, used only for relatively low-volume niche applications. But Joseph Poon, a materials physicist at the University of Virginia, has created laboratory samples of vitreous stainless steel that could propel amorphous metal toward ubiquity. He won’t reveal the exact components but says, “we’ve made it in thicknesses of about the one-centimeter range. The cost commercially would be about the same as the highest form of stainless steel, two or three bucks a pound.” That stuff would be the strongest metal ever made; a rod one inch in diameter would lift 550,000 pounds. The next step, Poon says, is engineering a hybrid version that contains crystals to solve the catastrophic shear failure problem.
“I am shocked at the progress we have made,” says Leo Christodoulou, who heads the Defense Advanced Research Projects Agency’s structural amorphous metals program, which funds Poon’s work and much of Johnson’s. When the program began in 2000, the greatest thickness achieved for amorphous steel was roughly one-thousandth of an inch.
Atomistic modeling will lead to the next breakthrough, Poon says. The traditional method of finding promising alloys was simply to make mix after mix in the lab, a development technique Poon calls “the monkeys-on-a-typewriter thing.” But computer modeling the atomic behavior of various combinations of elements is proceeding rapidly. “Atomistic modeling will help us find the sweet spot where it’s most useful to focus the alloy design work,” Poon says.
Back in Pasadena, down the hall from Johnson’s office, Jason Kang is investigating that sweet spot in the realm of titanium-zirconium–based amorphous alloys similar to Liquidmetal2. Every day he puts pea-size chunks of metallic elements into little crucibles, then zaps them to about 3,000°F with an electrical arc to make an alloy. If upon solidifying the resulting metallic “button” is reflective like a mirror, he knows instantly that he has made a glass. The surface reflects for the same reason the surface of a liquid reflects—the amorphous atoms form a smooth skin that bounces light uniformly. “That’s why you don’t have to machine it after casting,” says Kang, gazing fondly at it. “It just pops out of the mold looking like this.”
Johnson hopes that eventually the world’s engineers and architects will be able to choose from a panoply of amorphous metals and that the catastrophic shear failure problem will be solved for all of them. There will be cheap, abundant vitreous steel, and metalworking factories will be refitted to exploit the material’s boons. The first nation to achieve that happy state will boast greener, safer vehicles, better homes and buildings, more potent arms and sturdier defenses, more efficient industries, and even more successful golfers, batters, and tennis players. “I think we can get there,” Johnson says, admiring the jumble of trinkets before him. “I think all metals will eventually be vitreous. There is a fantastic future.”
