While most metals feature some degree of elasticity, some respond better than others to being bent out of shape. Scientists experimenting with the makeup of these materials have developed a novel, copper-based alloy they say would be simple to produce at scale, and boasts unparalleled elasticity at room temperature.
For a metal to have high elasticity, it needs to be easily stretched and deformed, measured by what’s called Young’s modulus, while still being strong enough to return to its original form. Integrating these properties into metals and alloys is a tricky balancing act, with one often compromising the others, but through careful engineering materials can be produced to meet specific requirements for everyday applications.
One example is stainless steel, which has a high tensile strength and is resistant to a wide range of temperatures and corrosion, and is therefore used in everything from cookware, to operating theaters, to outer space. You mightn’t know it by looking at your saucepan, but stainless steel even has a tiny amount of give in it, with an elastic strain value of <0.2%.
This goes for many metals and alloys, which in their bulk form exhibit an elastic strain value of under 1%, (though on micro and macro scales this figure sits at about 10%). Engineers at Tohoku University have put forward a new copper-based alloy that takes these type of bulk metals into flexible new terrain.
The team’s copper-based single crystalline alloy in bulk form is remarkably strong and features an exceptionally high tensile elastic strain of 4.3% at room temperature, which is said to be unmatched among such materials. It does so in a way that defies what’s known as Hooke’s law, which says that the elasticity of a material is proportional to the stress applied, by being highly elastic even when subjected to only small amounts of stress.
This type of material could be put to use in everything from more flexible sporting goods to advanced medical implants that better conform to the human body. The scientists are now exploring these possibilities while further studying the performance of the alloy to ascertain its functional fatigue after such large deformations. Promisingly, they say the cyclic heat treatment used to prepare the alloy’s single crystals is a simple process that lends itself well to mass production.
"Our bulk alloy can be used as spring materials with high recoverability, and they could also be applied to devices that employ strain-mediated sensors, such as stretchable electronics" said Sheng Xu, who led the research. "The new alloy's low Young's modulus resembles human bones and therefore has the potential for use in medical applications."
The research was published in the journal Nature.
Source: Tohoku University
