Nadred, December 9 (European Press) –
Scientists have measured the highest hardness ever recorded, of any material, while examining a metal alloy it is made of Chromium, Cobalt, and Nickel (CrCoNi).
Not only is metal highly ductile, which in materials science means it’s highly ductile and impressively strong (meaning it resists permanent deformation), Instead, its strength and ductility improve as it cools. This is in contrast to most other existing materials.
The team, led by researchers from Lawrence Berkeley National Laboratory (Berkeley Lab) and Oak Ridge National Laboratory (ORNL), published a study describing their unprecedented findings in the journal Science.
“When you design structural materials, you want them to be strong but also flexible and resistant to fracture,” he said. It’s a statement Project co-director Easo George, an expert in advanced alloy theory and development at ORNL and the University of Tennessee. “There is usually a middle ground between these properties. But this material is both, and instead of becoming brittle at lower temperatures, it becomes stronger.”
CrCoNi is a subgroup of a class of metals called high-entropy alloys (HEAs). All alloys used today have a high content of one element with lower amounts of additional elements added, But HEAs are made from an equal mixture of each ingredient.
These balanced atomic recipes seem to give some of these materials an extremely high combination of strength and ductility upon stress, which together make up what is called “toughness”.
HEAs have been a hot area of research since they were first developed some 20 years ago. But the technology to push materials to their limits in extreme testing wasn’t available until recently.
“The hardness of this material is near liquid helium temperatures (20 K) up to 500 MPa rms. In the same units, the stiffness of a piece of silicon is one, that of an aircraft aluminum frame.” The stirrups are about 35 and the hardness of some of the best steels is about 100. So the number 500 is an amazing number.said research co-leader Robert Ricci, a senior faculty scientist in Berkeley Lab’s Materials Science division.
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