Reliable Alloy that Refuses to Forget, Repeatedly

Low-fatigue material remembers its shape, despite being transformed over 10 million times, could upgrade solar devices.

Image courtesy of Rodrigo Lima de Miranda and Eckhard Quandt, ACQUANDAS
Shape memory alloys are used in coronary stents that expand in arteries to hold vessels open. Scientists discovered a new alloy to replace the nickel and titanium in the above stent to increase performance over repeated deformations.

The Science

Withstanding over 10 million transformations and breaking previous records, a shape memory alloy has been discovered with ultralow-fatigue performance. After repeated deformations, previous shape memory alloys started to lose their ability to revert back to their original shape after being deformed. This alloy contains precipitates that act as sentinels that ensure complete and reproducible transformation after each deformation.

The Impact

This discovery opens avenues for shape memory alloys into everyday products. Low-fatigue shape memory alloys could be developed for products that must withstand repeated deformations, such as artificial heart valves, refrigeration components, and solar energy conversion devices.

Summary

Shape memory alloys, metals that return to their original shape after deformation – typically by applying heat, have been available for decades and are used in commercial items such as frames for glasses or stints for arteries in medical applications.  However, these alloys cannot be used in many applications because they lose their shape memory following repeated deformations. Researchers at the University of Maryland and University of Kiel discovered a new alloy based on titanium, nickel, and copper (TiNiCu) that reliability withstood over 10 million deformations. In shape memory alloys, the arrangement of the atoms can switch between two different configurations. This transition can be triggered by heat or releasing tension. The ultralow-fatigue alloy exhibited nearly identical deformation cycles over 10 million times. Advanced characterization of this shape memory alloy revealed that precipitates (composed of Ti2Cu) assured that the phase transformation proceeded towards completion after each deformation. Because the new shape memory alloy has proven to have a lifespan that can withstand repeated deformations, researchers predict applications such as heart valve technology, refrigeration, and solar energy conversion devices could be changed forever.

Contact

Manfred Wuttig
University of Maryland
wuttig@umd.edu

Funding

U.S. Department of Energy, Office of Science, Basic Energy Sciences including support for research the Advanced Photon Source, an Office of Science User Facility, and Deutsche Forschungsgemeinschaft (University of Kiel)

Publications

C. Chluba, W. Ge, R. Lima de Miranda, J. Strobel, L. Kienle, E. Quandt, and M. Wuttig, “Ultralow-fatigue shape memory alloy films.” Science 348, 1004 (2015). [DOI:10.1126/science.1261164]

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