Searching For A Glass Stronger Than Steel, Researchers Devise New Method For Quicker Identification
Bulk metallic glasses (BMG) are a class of pliable glass with high yield strength and applications in a variety of technologies. But their multicomponent nature imposes a challenge for their discovery process. Scientists at Yale University have now come up with an astonishingly fast and accurate method to identify the elements that make durable and versatile BMGs.
These amorphous glassy structures are metal alloys, composed of three or more metals such as magnesium, copper, and yttrium (Mg-Cu-Y). The mechanical and physical properties of BMGs depend strongly on the concentrations of the chemical elements that make up the alloy. And when the correct combination of elements are heated or cooled at specific temperatures at specific rates the resulting materials are several times stronger than steel and considerably stronger, yet more elastic.
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The ability to produce hard, long-lasting, and complex shapes has made BMGs useful for high-performance engineering materials, cosmetic applications; as replacements to plastic, such as in watches, cell phones, and biomedical technology; and also to make sporting equipment like golf clubs.
Identifying the alloys that make BMGs using traditional methods is a tedious process and it usually takes a full day to identify a single metal alloy that constitutes a BMG. It has been estimated that only a minute fraction of the potential bulk metallic glass formers have been explored so far. A new method devised by Jan Schroers, a professor of mechanical engineering and materials sciences, and his team, can screen up to 3,000 alloys per day and simultaneously ascertain certain properties, such as melting temperature and malleability.
"Instead of fishing with a single hook, we're throwing a big net," Schroers said in a press release. "This should dramatically hasten the discovery of BMGs and new uses for them."
He said that there are an estimated 20 million possible BMG alloys. About 120,000 metallic glasses have been produced and characterized to date.
Without this new method it would take alloy makers about 4,000 years to sift through all the likely combinations. But Schroers' new method can do it in just four years. The new method combines a process called parallel blow forming with combinatorial sputtering. Blow forming generates bubble gum-like bubbles from the alloys and indicates their pliability. Co-sputtering is used for fabricating thousands of alloys simultaneously. Alloy elements are mixed at various predefined ratios and temperatures, yielding thousands of millimeter-sized, micron thick samples. "Instead of blowing one bubble on one material, we blow-form 3,000 bubbles on 3,000 different materials," Schroers said.
Schroers and his team started their research in 2010 and have since tested about 50,000 alloys and identified three new BMG alloys. They are focused on 10 alloy families. Some of the elements that constitute a BMG may be expensive but the team's goal is to find BMG's which are durable, biocompatible, elastic, and affordable.
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