Bulk Metallic Glasses Are Strong Like Steel, Mold Like Plastic


Jan Schroers and his team have created metal alloys capable of being blow molded into any shape  (Source: Yale University)

These moldable, yet strong metal alloys coupled with a new processing technique has created a time and energy-saving method for developing useful materials

Yale University scientists have created a material that is strong and durable like steel, yet is capable of being blow molded into a variety of shapes like plastic.

Jan Schroers, study leader and materials scientist at Yale University, and a team of researchers, have developed alloys that are low-cost to process and can be molded like plastic, but does not compromise strength.
The material is bulk metallic glasses (BMGs), which are metal alloys have randomly arranged atoms instead of the uniform, crystalline structure found in most metals. Most metals cannot be molded like plastics, and most plastics do not have the strength of metal, but these alloys share the characteristics of both materials. They are made up of different metals such as nickel, titanium, copper and zirconium.
The materials for BMGs cost about as much as high-end steel, but can be processed like plastic for lower costs. Schroers and his team softened the BMGs by blow molding them at low pressures and low temperatures, making the alloys to flow much like plastic without crystallizing like metal. This allowed the team to mold and shape the BMGs with ease. But to keep the low temperature and low pressure for molding, they shaped the BMGs in fluid or in a vacuum.
“The trick is to avoid friction typically present in other forming techniques,” said Schroers. “Blow molding completely eliminates friction, allowing us to create any number of complicated shapes, down to the nanoscale.”
By using this process, the team combined all three steps for conventional metal processing into one. The three steps are shaping, joining and finishing, and their process for blow molding the alloys has combined the three into one, saving time and energy. Processing for these BMGs takes less than one minute.
“This could be a whole new paradigm for shaping metals,” said Schroers. “The superior properties of BMGs relative to plastics and typical metals, combined with 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.”
Schroers and his team have already put their new processing technique to work by fabricating miniature resonators for microelectromechanical systems, which are small, electric-powered mechanical devices. It has also been used to fabricate gyroscopes.

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