A team of Chinese scientists has created a new ultra-strong, ultra-ductile steel that is so strong a fingernail-sized piece can support two tonnes without failing.
The metal is well-suited to several industrial applications, including aerospace, motor vehicles, military and heavy machinery.
Jointly developed by Northwestern University in Shenyang, the Shenyang National Laboratory for Materials Science, Jiangyin Xingcheng Special Steel Works and German-based Max Planck Institute for Iron Research, their work was published in the peer-reviewed journal, Science.
Metallurgists will tell you that the relationship between the strength and malleability of metals is inverse. That is to say, when you make a metal stronger, its ability to bend and stretch is diminished.
The Chinese-led team developed a novel hierarchical nanostructure design to create an alloy with high levels of UTS and the ability to stretch between 18-25%.
For comparison’s sake, a single gram of gold – one of the most malleable metals on the periodic table – can stretch up to two kilometres before failing.
First, the team forged melted raw steel alloy at a temperature between 650-800 degrees Celsius before letting the superheated mass air cool.
The metal was cooled further after being subjected to a bath of liquid nitrogen at a frigid minus 196 degrees Celsius, before receiving a final heat treatment at 300 degrees Celsius.
The tempering process strengthens the bonds of the metal at a molecular level, greatly improving its ability to deal with impact stress.
The forge melting process, which involves heating and shaping raw metals, was preferable to the standard method of creating super strong steel from sheets of metal, said lead author of the research paper and scientist at Northwestern University, Li Yunjie.
In the research paper, Li said his team’s new metal had a strength index of two gigapascals, one of the highest tensile strengths attainable.
Their new process could reduce the manufacturing cost of steel by about $75 per tonne and cut emissions by 100 kilograms of coal per tonne of steel produced, according to Li.
He added that the highly desirable steel had economic benefits while simultaneously promoting “green development”.
The next step for Li and his colleagues is finding practical scenarios where the metal’s robustness can be tested.
The material was well-suited to transport and logistics, said Geoffrey Brooks, a researcher from the Swinburne University of Technology in Melbourne.
Engineers could build vehicles with less material, resulting in lighter, more fuel-efficient designs.