Japanese scientists have created an alloy that is as hard as steel but expands like rubber when environmental conditions change while also being 20 times more flexible than conventional alloys.
A highly flexible alloy, created from titanium and nickel metals by researchers at Japan’s National Institute for Materials Science (NIMS), could be a key ingredient in building morphing aircraft or super-strong artificial muscles.
Morphing aircraft remain a science fiction concept as scientists have struggled to develop a material that is flexible enough to achieve the morphing effect and strong enough to withstand the rigors of flight. However, an alloy that is as strong as steel but can stretch like rubber when environmental conditions change could offer hope for the development of special flying devices.
Previous research has established that the titanium-nickel alloy has unique properties, such as the ability to stretch to much higher limits than other metal alloys while still retaining a new shape. When the alloy’s temperature increases, it can also return to its original shape.
While this makes the alloy a great candidate for building morphing aircraft, researchers have had difficulty using it due to temperature limitations at which the alloy can maintain these properties.
Although the material is strong and flexible, it only displays these properties at specific temperatures, significantly limiting its applications. A research team led by Professor Xiaobing Ren at NIMS has devised a three-step process to make the alloy display these properties over a wide temperature range.
First, they deformed and stretched the alloy by more than 50%, then heated it to 300 degrees Celsius before stretching it again.
In the final step, the researchers only stretched the alloy by 12 percent, but in the end, the material was capable of withstanding pressures of about 18,000 times normal atmospheric pressure, making its strength performance comparable to steel while also being 20 times more flexible than conventional alloys.
More importantly, the titanium-nickel alloy also exhibits this property over a wide temperature range from -80°C to 80°C.
Speaking to New Scientist, Professor Ren explained that the alloy displays these properties because it is more like a glass than a metal. Compared to regular glass, the alloy has areas of “grain” deformation.
Simply put, alloys have regions where the molecules are arranged in a way that supports the deformation of the material rather than breaking. The absence of these deformable grains in glass makes it brittle, while their presence makes the material extremely flexible.
According to the research team, the method of developing the material is quite simple, it can be easily reproduced in other laboratories and can be applied industrially on a large scale.