Scientists have identified an alloy of cobalt, nickel, and chromium as the toughest one known.
The team, led by researchers from the Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory, reported encouraging results regarding CrCoNi. All components of this material are mixed in equal proportions. This is a rare feature: alloys usually mix the constituents differently. But most importantly, the performance properties of this mix are unique.
“When you design structural materials, you want them to be strong but also ductile and resistant to fracture... Typically, it’s a compromise between these properties. But this material is both, and instead of becoming brittle at low temperatures, it gets tougher.”
The alloy showed very high strength properties, which only increased with extreme cooling. The same "inadequate" behavior was shown by impact toughness parameters, i.e. deformation resistance and ductility. Steel, even its best varieties, become brittle in such circumstances, whereas the new material, on the contrary, only gets stronger.
“The toughness of this material near liquid helium temperatures (20 kelvin, -424 Fahrenheit) is as high as 500 megapascals square root meters. In the same units, the toughness of a piece of silicon is one, the aluminum airframe in passenger airplanes is about 35, and the toughness of some of the best steels is around 100. So, 500, it's a staggering number.”
The result of the newly created material is due to the fact that when temperatures fall to critical levels, it fundamentally changes its crystalline lattice: from cubic to hexagonal. This behavior of the atomic structure allows metals both to keep flowing and keep meeting new resistance from obstacles on a much more immense level.
The material is unlikely to be used in everyday life, especially since cobalt and nickel are in short supply these days. But it is likely to become more widely used in the space industry and in the production of equipment used in the Arctic.