By: Inspenet, December 15, 2022.
Engineers in the USA They obtained a metal alloy with the highest fracture toughness ever measured in a material on Earth. The material, made up of chromium, cobalt and nickel (CrCoNi), has extremely high strength and ductility. Furthermore, and counterintuitively, these properties increase as the material cools, suggesting interesting potential for applications in extreme cryogenic environments, the developers reported.
“When you design structural materials, you want them to be strong, but also ductile and resistant to fracture,” said metallurgical engineer Easo George of the University of Tennessee and one of the paper’s authors. “Usually it’s a compromise between these properties. But this material is both, and instead of becoming brittle at low temperatures, it becomes stronger,” he explained.
Hardness, ductility and toughness are three properties that determine the durability of a material. Hardness describes resistance to deformation and ductility describes how malleable a material is. These two properties contribute to its overall toughness: the resistance to fracture. Generally, toughness increases with increasing temperature.
George and another author, mechanical engineer Robert Richie of the University of California at Berkeley, have spent some time working on a class of materials known as high-entropy alloys (HEAs). Most alloys are dominated by one element, with small proportions of others mixed in, while HEAs contain mixed elements in equal proportions.
During their research, the scientists noticed that the strength and ductility of the new material increase at the temperature of liquid nitrogen (-196 °C) without compromising its toughness. The team took the experiment one step further, at liquid helium temperatures (-253°C). The results were more than surprising. “The hardness of this material near liquid helium temperatures is as high as 500 megapascals per square meter,” Ritchie said.
“In the same units, the hardness of a piece of silicon is 1, the aluminum frame of airliners is about 35, and the hardness of some of the best steels is around 100. So 500 is a number amazing,” he said.
Source: https://actualidad.rt.com/actualidad/451736-desarrollan-aleacion-tenaz-conocida-tierra
Photo : Robert Ritchie/Berkeley Lab
Cover Photo : Microscopy showing the trajectory of a fracture and the deformation of the crystalline structure in the CrCoNi alloy.
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