August 15, 2015
Professors Manfred Wuttig and Eckhard Quandt at the Universities of Maryland, USA and 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. This makes the new alloy, a mixture of titanium, nickel and copper, 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.
All shape memory alloys are phase-changing materials, meaning they can shift into different molecular configuration—such as 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 Quandt discovered that the key to the alloy’s durability was the presence of a small impurity, a precipitate 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 thereby reducing fatigue.