New Shape Memory Alloy Withstands 10 Million Deformations

University of Maryland professor Manfred Wuttig (Department of Materials Science and Engineering/Maryland NanoCenter) and his colleagues at the University of Kiel, Germany have produced a new shape memory alloy so tough it returns to its original shape even after being bent and heated over ten million times. The new material, recently described in Science and profiled by BBC News, could be used to create and improve products ranging from biomedical devices to refrigerators.

Lightweight and elastic, shape memory alloys have been used in a wide variety of products, such stents that open blocked arteries, fire protection systems, eyeglass frames, robotics, actuators, surgical tools, orthodontic wires, aerospace components, and even underwire bras. Eventually, all shape memory alloys wear out, which so far have made them unsuitable for long-term use.

Wuttig’s alloy, a mixture of titanium, nickel and copper, has been shown capable of withstanding ten million cycles of deformation, making it a candidate for “high cycle” applications, such as artificial heart valves and solid state air conditioners. In contrast, the previous highest-performing shape memory alloy could be deformed approximately 16,000 times before it succumbed to fatigue. In an editorial published in the same issue of Science, that material’s inventor, Professor Richard D. James (University of Minnesota), described Wuttig’s as “a breathtaking development.”

All shape memory alloys are phase-changing materials, meaning they can shift into different molecular configuration; for example, water into ice. The new alloy’s transition can be “activated” by heat in one of its forms, and by a release of tension in another. Wuttig and his team discovered that the key to the alloy’s durability was the presence of a small impurity, a precipitate composed of titanium and copper (Ti₂Cu). These particles were compatible with both of the alloy’s phases, allowing it to mediate millions of complete and reproducible transformations while reducing fatigue.

For More Information:

Christoph Chluba, Wenwei Ge, Rodrigo Lima de Miranda, Julian Strobel, Lorenz Kienle, Eckhard Quandt, Manfred Wuttig. "Ultralow-fatigue shape memory alloy films." Science, 348(6238), 1004-1007. 29 May 2015. DOI: 10.1126/science.1261164 Abstract »

Richard D. James. “Taming the temperamental metal transformation.” Science, 348(6238), 968-969. 29 May 2015. DOI: 10.1126/science.aab3273 Abstract »

Jonathan Webb. "Memory alloy bounces back into shape 10 million times." BBC News. Retrieved 29 May 2015 from http://www.bbc.com/news/science-environment-32886000.

Published June 2, 2015