An alloy of titanium and nickel is as strong as steel but stretches like a rubbery polymer. With some clever engineering, it may eventually lead to technologies like shape-shifting aircraft.
Imagine a plane with long wings that contract in midair to become shorter 鈥� and make the craft more aerodynamic 鈥� as it gains speed. To make this futuristic technology, engineers would need a material that is stretchy enough to change shape yet strong enough to withstand the elements during flight. at the National Institute for Materials Science in Japan and his colleagues have created a substance that may fit the bill.
The researchers knew that alloys of nickel and titanium can have special properties like stretching more than other metals and 鈥渞emembering鈥� their shape 鈥� if deformed then heated up, they will revert to their original form. Although previous work has produced elastic and strong versions of these alloys, says Ren, the materials only displayed these properties at set temperatures, which limited their applications.
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So the team developed a three-step procedure that would make one such alloy both elastic and strong at a large range of temperatures. First, they severely deformed their sample, elongating it by 50 per cent, then briefly heated it to 300掳C (572掳F) and finally elongated it again, this time only by 12 per cent.
At the end of the process, the material could withstand pressures about 18,000 times greater than atmospheric pressure. This is comparable to the strength of steel, but the new alloy was also about 20 times more elastic than that metal. And it maintained these properties at all temperatures between -80掳C and 80掳C (-112掳F and 176掳F).
The material has these properties because it isn鈥檛 just metal-like but also qualifies as a kind of glass, says Ren. While conventional glasses tend to be brittle, this type contains some 鈥渟eeds鈥� of deformation: regions where the molecules are arranged in such a way that the material can change shape rather than breaking apart under tension.
at the Institute of Physics of the Czech Academy of Sciences says that the procedure the researchers have developed could be easily adopted by existing industrial facilities, so the new material could be produced at scale beyond the lab. However, says Ren, many engineering questions will have to be addressed before shape-shifting aircraft can become a reality.
Nature
