Metallic Glass: The Next Super Material

Apple Computer has been acquiring patent rights on a class of remarkable new materials that may help it create super strong and tough cases for iPhones, laptop computers and other portable devices, using energy-saving production methods.

That’s according to Professor Robert Ritchie, chair of the Department of Materials Science and Engineering at UC Berkeley and a leading researcher on “metallic glasses.” These unique materials are alloys of several metallic elements, but without the orderly, crystalline structure of normal metals. (“Glass” is a generic term referring to any disordered, or amorphous, material.)

Most materials experience a tradeoff between strength (hardness) and toughness (resistance to breaking or fracture). Engineers have to find the right combination for the job. It may be counterproductive to use a strong but brittle material that fractures when stressed.

Metallic glasses can be made remarkably free of such tradeoffs, Ritchie told me. One of his new formulations is as strong as the hardest steel but three times tougher; at the same time, it is three times stronger than the toughest steel.

Materials scientists are making rapid progress in learning how to form parts out of metallic glass, using some of the same cheap, quick and energy-saving processes used to shape plastic.

A team led by researchers at the California Institute of Technology just reported in Science magazine that heating metallic glass with short pulses of electrical current allows it to be molded into virtually any shape—what they are touting as “a paradigm shift in metallurgy.”

We’ve taken the economics of plastic manufacturing and applied it to a metal with superior engineering properties,” said one researcher. “We end up with inexpensive, high-performance, precision . . . parts made in the same way plastic parts are made—but made of a metal that’s 20 times stronger and stiffer than plastic.”

A team at Yale University has used different techniques to achieve the same result—forming complex parts as easily as with plastic. As proof of concept, they’ve fabricated seamless bottles, watch cases and biomedical implants.

Their techniques “have the potential to impact society just as much as the development of synthetic plastics and their associated processing methods have in the last century,” boasted one of the team members.

For major applications such as aerospace, however, UC’s Ritchie is a good deal more cautious, noting that “new structural materials can take decades to get into applications.”

Some of the most revolutionary materials, like fiber composites, were first used in tennis racquets and golf clubs long before they were used for aircraft airframes, for example. Metallic glass has already been tried in commercial golf clubs, but lost out to titanium.

But Ritchie—and apparently, Apple as well—believes metallic glass would be ideal for making cases for laptops and other consumer electronics because it’s exceptionally tough, strong and easy to cast with high precision. “You’ll see them soon,” he predicts.

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