Drawing inspiration from the structure of bones and bamboo, researchers have created stronger, tougher materials that can be customised for a wide variety of applications - from body armour to automobile parts.
A metal, in general, is composed of millions of closely-packed grains. The size and disposition of those grains affects the metal's physical characteristics.
"If we gradually increase the size of the grains lower down in the material, we can make the metal more ductile. You see similar variation in the size and distribution of structures in a cross-section of bone or a bamboo stalk," explained Xiaolei Wu, professor of materials science at the Institute of Mechanics in the Chinese Academy of Sciences.
In short, the gradual interface of the large and small grains makes the overall material stronger and more ductile, which is a combination of characteristics that is unattainable in conventional materials.
"We call this a gradient structure, and you can use this technique to customise a metal's characteristics," Wu added.
Wu and Yuntian Zhu, professor of materials science and engineering at North Carolina State University, collaborated on research that tested the gradient structure concept in a variety of metals, including copper, iron, nickel and stainless steel.
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The technique improved the metal's properties in all of them.
The research team also tested the new approach in interstitial free (IF) steel, which is used in some industrial applications.
"We think this is an exciting new area for materials research because it has a host of applications and it can be easily and inexpensively incorporated into industrial processes," Wu noted.
The two papers were published in Materials Research Letters and Proceedings of the National Academy of Sciences.