In 1960, the first metallic glass was developed at the California Institute of Technology. A metallic glass is an alloy that’s been heated up and then cooled down very quickly so that it doesn’t have a chance to form crystals, allowing the material to keep its amorphous structure. Thus, metallic glass is stronger than steel or titanium and just as tough, and 20 times stronger and stiffer than plastic. Metallic glass is an ideal material for everything from cellphone cases to aircraft parts.
The problem with metallic glass is that it’s difficult to mold and shape. Heat takes time to distribute through it, so the glass is generally molded at temperatures above 1000 degrees Celsius, which is hard on molds and is too expensive and impractical. However, now researchers have found a cheaper way to produce metallic glass. The researchers found that if they heated and processed the metallic glass fast enough, they could heat the metallic glass to a liquid state that’s fluid enough to be injected into a mold and can freeze before it crystallizes.
“We’ve taken the economics of plastic manufacturing and applied it to a metal with superior engineering properties,” says William Johnson, the Ruben F. and Donna Mettler Professor of Engineering and Applied Science. “We end up with inexpensive, high-performance, precision net-shape 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 net-shape part is a part that has acquired its final shape.
To heat the material uniformly and rapidly, they shot a high-energy electric pulse into a small rod of metal alloy, to a temperature of 550 degrees Celsius in only half a millisecond. Then, the softened glass was injected into a mold, the desired shape formed and cooled in 40 milliseconds. Because the material can be heated uniformly, only half the temperature is needed. This also means the materials needed to form the mold can be less expensive and replaced less often.
With metallic glass being 20 times stronger than plastic and potentially becoming just as cheap to produce, we would most likely see it replace plastic in products to make them stronger. Like Apple is using a type of Liquid Metal in the iPhone so their screens don’t break so easily. The researchers are publishing their findings in the journal Science.
Photo: A metallic-glass rod before heating and molding (left); a molded metallic-glass part (middle); the final product with its excess material trimmed off (right). [Credit: Marios D. Demetriou]