A Yale University team led by Jan Schroers, a materials scientist, are showing that some recently developed bulk metallic glasses (BMGs) that are metal alloys with randomly arranged atoms instead of the orderly, crystalline structure found in ordinary metals – can be blow molded like plastics into complex shapes that can’t be achieved using regular metal, yet without sacrificing the strength or durability that metal affords.

The findings are described in full online in the current issue of the journal Materials Today.

These aren’t going to be cheap.  The alloys Schroers’ team uses are made up of different metals, including zirconium, nickel, titanium and copper.  It’s not platinum, but Schroers points out the materials cost about the same as high-end steel, but can be processed as cheaply as plastic.  With that one’s imagination takes off – lots of castings might as well be hollow. . . And if they can be welded . . .  Saving lots of mass . . .  You see where this writer is going.

Jan Schroers with a Metal Blow Molded Bottle.

Schroers work allows imagining materials that are stronger than steel, but just as versatile as plastic, able to take on a seemingly endless variety of forms. For decades, materials scientists have been trying to come up with just such materials, ones that could be molded into complex shapes with the same ease and low expense as plastic but without sacrificing the strength and durability of metal.  The die, if you’ll pardon the metaphor, is now cast.

Schroers explains, “These alloys look like ordinary metal but can be blow molded just as cheaply and as easily as plastic.”  So far the team has created a number of complex shapes-including seamless metallic bottles, watch cases, miniature resonators and biomedical implants – that can be molded in less than a minute and are twice as strong as typical steel.

Less than a minute? Compare that to weld up or machined fabrication.  The labor and fabrication expense might make the materials seem cheap.

By blow molding the BMGs, the Yale team is able to combine three separate steps of traditional metal processing (shaping, joining and finishing) into one, allowing the team’s process to carry out previously cumbersome, time- and energy-intensive processing in less than a minute.

Technically speaking, the team blow molds 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. The press release quotes Schroers saying it’s the low temperatures and low pressures that allowed the team to shape the BMGs with unprecedented ease, versatility and precision,. In order to carefully control and maintain the ideal temperature for blow molding, the team shaped the BMGs in a vacuum or in fluid.

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

Schroers and his team are already using their new processing technique to fabricate miniature resonators for microelectromechanical systems (MEMS)-tiny mechanical devices powered by electricity-as well as gyroscopes and other resonator applications.

Summing up, Schroers says, “This could enable a whole new paradigm for shaping metals. 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.”

That might just be an understatement.  As the technology spreads with others adding more innovation, sparks lots of imaginative thought into the possibilities, like a truly rugged laptop case. Please?

Yale's Metal Blow Mold Examples. Click image for more info.

There is the reality check – this work is step one, a successful start.  The catch is the team is making really good models at less than about 2 centimeters, eight tenths of an inch.  This should improve quickly.  The heat requirements while quoted above as low, start where plastics stop, suggesting the equipment needs will be substantially different.

On the other side of reality the pressures needed patterns much like plastic implying the engineering won’t be so different.  Also shrinkage from cooling is greatly reduced and precise dimensions are much more easily achieved.  Molds can include inversions and functions such as fastener sites.  Surfaces with engravements or embossments can be integrated as well.

The other people on the team deserve note.  They are Thomas M. Hodges and Golden Kumar at Yale University; Hari Raman and A.J. Barnes at SuperformUSA; and Quoc Pham and Theodore A. Waniuk at Liquidmetal Technologies.

Blow molding metals is an idea with a solid foothold in reality now.  There’s a long way to go in dimensions and other materials.  For saving raw materials, cutting back on energy used, reducing unit costs, increasing strength and reducing weight – it’s a happy future in the materials business.


2 Comments so far

  1. Getting started with Google SketchUp : Cars Blog | Everything You should Know about Cars on March 1, 2011 6:55 AM

    […] Now Metal Bottles and Other Blown Metal Shapes | New Energy and Fuel […]

  2. Musson on March 1, 2011 8:20 AM

    Thanks for sharing this article. Blow molding metal could have some serious impact on manfacturing.

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