Versatile alloy delivers extra bounce

RUTGERS (US) — A class of high-strength metal alloys could be a hundred times more responsive than existing materials, making springs, sensors, and switches smaller and more responsive.

The pliant alloys could be used in blood vessel stents, sensitive microphones, powerful loudspeakers, and components that boost the performance of medical imaging equipment, security systems, and clean-burning gasoline and diesel engines.

“We have been doing theoretical studies on these materials, and our computer modeling suggests they will be super-responsive,” says Armen Khachaturyan, professor of materials science and engineering at Rutgers.

The metals, embedded with nanoparticles, can be highly elastic, or “springy,” and can convert electrical and magnetic energy into movement or vice-versa.

The research is reported in the journal Physical Review Letters.

One class of these so-called “functional materials” generates an electrical voltage when the material is bent or compressed. Conversely, when the material is exposed to an electric field, it deforms.

These piezoelectric materials are used in ultrasound instruments; audio components such as microphones, speakers and record players; autofocus motors in some camera lenses; spray nozzles in inkjet printer cartridges; and several types of electronic components.

Another class of functional materials sees changes in magnetic fields deform the material and vice-versa. These magnetorestrictive materials have been used in naval sonar systems, pumps, precision optical equipment, medical and industrial ultrasonic devices, and vibration and noise control systems.

The “decomposed two-phase nanostructured alloys” form by cooling metals that were exposed to high temperatures where the nanosized particles of one crystal structure, or phase, are embedded into another type of phase.

The resulting structure makes it possible to deform the metal under an applied stress while allowing the metal to snap back into place when the stress is removed.

These nanostructured alloys might be more effective than traditional metals in applications such blood vessel stents, which have to be flexible but can’t lose their springiness.

In the piezoelectric and magnetorestrictive components, the alloy’s potential to snap back into shape after deforming—a property known as non-hysteresis—could improve energy efficiency over traditional materials that require energy input to restore their original shapes.

In addition to potentially showing responses far greater than traditional materials, the new materials may be tunable; that is, they may exhibit smaller or larger shape changes and output force based on varying mechanical, electrical or magnetic input and the material processing.

Researchers from the University of Maryland contributed to the research, funded by the National Science Foundation and the U.S. Department of Energy.

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