Memory alloys that spring back into a pre-defined shape are nothing new, but regular bending means they fatigue and fail within a relatively short time-scale. Now, a team of engineers has developed an alloy that rebounds into shape even after 10 million bends.
Existing memory alloys have found plenty of uses, in everything from flexible glasses frames to medical implants that open up blood vessels. But in these applications, they can typically undergo just a small number of large deformations before they break.
The new alloy, which is made from nickel, titanium and copper, has a special crystal structure that allows it to undergo bending more easily than most metals. The constituent atoms are arranged in a way that allows them to switch between two different configurations, over and over. This is known as a phase transition, and it can can occur either with changes in temperature or merely the release of tension.
The team, based at the University of Kiel in Germany, actually found that a small quantity of titanium-copper impurities, Ti2Cu, that they added helped that phase transition to happen. As a result—and after weeks of machine-enabled testing—they found that the sample could survive being bent over 10 million times. The result are published in Science.
The researchers suggest that the new material could be used in situations where loading varies constantly, like in the wings of aeroplanes, or where materials undergo regular heating and cooling. [Science via BBC]
Image by University of Kiel