Sunday, April 2, 2023

Scientists have discovered the toughest known material at ultra-cold temperatures

It can be potentially used as structural or load-bearing components for many potential applications.

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Structural materials have good fracture properties at very low temperatures. It is important for fields such as space exploration.  

As all know, what is the toughest material on Earth?’ that is ‘Diamond.’ It will jump out on the top line. Diamond is the hardest known material, but its hardness is usually related to the strength of the material. Diamond is tough and strong.

The University of Bristol has discovered an alloy that shows increased strength at over -250°C, making it the toughest material on record.

These findings are published in Science and show that chromium-cobalt-nickel alloy has a high fracture toughness at high temperatures. It could be used in extreme Earth and space environments. The behavior of this particular combination of metals is due to phase transformation. Therefore, when they are combined with other sensors, crack form, and they prevent propagation.

Lead author Dr. Dong Liu of Bristol’s School of Physics has discovered a high-entropy chromium-cobalt-nickel alloy with an incredibly high fracture toughness at 20 kelvin. It can be used as structural or load-bearing components for many potential applications in space and cold regions on Earth and other planets.

This behavior is caused by an unexpected phase transformation combined with other microstructures. It prevents the crack formation and propagation. The fracture toughness of this alloy is helpful for a range of cryogenic applications.

The study explained: “This is very interesting because most alloys become more brittle with a decrease in temperature. It refers to the sinking of liberty ships in WWII and the Titanic due to the metals losing their ductility at low temperatures.”

The scientist also discovered the mechanisms responsible for the improved strength and toughness. This means these processes can be used as a design guide for scientists and engineers to design better materials.”

They again said: “The experimental testing of the toughness of this material at 20K was not a trivial effort. It took us a few years to design and complete. The experiment’s success was based on our rich experience and strong expertise in testing materials under extreme conditions.”

Their team has a plan for untangling fundamental causes for the sequence of toughening mechanisms in this material at 20 Kelvin. For that, they used novel experimental and modeling methods. They also want to look at other types of high entropy alloys to see similar behaviors.

This study examined the fracture toughness values of the equiatomic CrCoNi and CrMnFeCoNi alloys at 20 kelvin (K).

Journal Reference:

  1. Dong Liu, Robert O. Ritchie et al. Exceptional fracture toughness of CrCoNi-based medium- and high-entropy alloys at 20 kelvin. Science. DOI: 10.1126/science.abp80
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