A button of yttrium-silver shows dents and deformations from repeated hammer blows. On the left are pieces of a brittle gadolinium-silicon-germanium intermetallic alloy that was shattered with just a light tap.
(Photo courtesy of the Department of Energy's Ames Laboratory.)
WHILE INTERMETALLIC MATERIALS (compounds consisting of two or more metals bonded together) are often superior to ordinary metals in terms of chemical, physical, electrical, magnetic, and mechanical properties, they're typically quite brittle. However, a discovery by researchers at the U.S. Department of Energy's Ames Laboratory at Iowa State University promises to open up new possibilities for these materials.
A research team led by senior metallurgist Karl Gschneidner Jr. and materials scientist Alan Russell has identified 12 rare-earth intermetallic compounds that are ductile at room temperature. "Many intermetallic materials are too brittle to handle," says Gschneidner. "If you drop them, they shatter. But you can beat on these new materials with a hammer, and they won't shatter or fracture — they're that ductile."
Such materials could be used to produce practical materials from coatings that are highly resistant to corrosion or that maintain strength at high temperatures to flexible superconducting wires and extremely powerful magnets. There may also be other applications for these ductile materials because of their high-temperature strength and/or corrosion resistance.
Research thus far has focused on yttrium-silver (YAg), yttriumcopper, and dysprosium-copper. However, a preliminary examination of other rare-earth compounds shows that ceriumsilver, erbium-silver, erbium-gold, erbium-copper, erbium-iridium, holmium-copper, neodymium-silver, yttrium-indium, and yttriumrhodium are also ductile.
In tensile-strength testing, these materials showed remarkable ductility. The YAg stretched nearly 25% before it fractured, compared to 2% or less for many other intermetallics. In other measurements, the materials showed American Society for Testing and Materials fracture toughness values (KIC) comparable with commercial aircraft-aluminum alloys.