New materials have steel's strength and plastic's moldability

Posted by Kate Taylor

Yale University scientists say they've come up with a set of new metals that are stronger than steel but as easy to mold as plastic.

A team led by materials scientist Jan Schroers has found that some recently-developed bulk metallic glasses - metal alloys with randomly arranged atoms rather than the standard crystalline metallic structure - can be blow molded like plastics.

"This could enable a whole new paradigm for shaping metals," says Schroers. "The superior properties of BMGs relative to plastics and typical metals, combined with the ease, economy and precision of blow molding, 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."

The end result is complex shapes that can't be achieved using regular metal, yet which still have their strength and durability. So far, the team has created seamless metallic bottles, watch cases, miniature resonators and biomedical implants, which can be molded in less than a minute and which are twice as strong as steel.

The materials cost about the same as high-end steel, Schroers said, but can be processed as cheaply as plastic. They are based on several different metals, including zirconium, nickel, titanium and copper.

The team blow molded the alloys at low temperatures and low pressures, where the bulk metallic glass softens dramatically and flows as easily as plastic but without crystallizing like regular metal.

In order to carefully control and maintain the ideal temperature for blow molding, the team shaped the BMGs in a vacuum or in fluid.

"The trick is to avoid friction typically present in other forming techniques," Schroers said. "Blow molding completely eliminates friction, allowing us to create any number of complicated shapes, down to the nanoscale."

In addition, by blow molding the BMGs, Schroers was able to combine three separate steps from traditional metal processing - shaping, joining and finishing - into one.

The team is already using its new technique to fabricate miniature resonators for microelectromechanical systems, as well as gyroscopes and other resonator applications.