18 January 2023
by Alex Brinded

Toughest material ever recorded

The chromium, cobalt and nickel alloy is reportedly extremely ductile and impressively strong.

Microscopy-generated images showing the path of a fracture and accompanying crystal structure deformation in the CrCoNi alloy at nanometer scale during stress testing at 20K (-253°C). The fracture is propagating from left to right © Robert Ritchie/Berkeley Lab

Unlike most materials, the alloy's strength and ductility were found to improve as the alloy gets colder. The team was led by researchers at the Berkely Lab and the Oak Ridge National Laboratory, USA.

CrCoNi is a subest of a class of metals called high entropy alloys or HEAs. While all alloys in use have a high proportion of one element, HEAs are an equal mix - which seem to result in extraordinarily high strength and ductility when stressed, hence toughness.

Although first developed around 20 years ago the technology to test them has only recently become available.

Co-leader Robert Ritchie at Berkeley said that the alloy's toughness near liquid helium temperatures (-253°C) is as high as 500MPa/m2, compared to silicon at 1MPa/m2 and aluminum airframes in a passenger planes at about 35MPa/m2. 'The toughness of some of the best steels is around 100MPa/m2. So, 500, it's a staggering number,' said Ritchie.

Authors

Alex Brinded

Staff Writer