(ORDO NEWS) — Scientists have recorded the highest impact strength for a metal alloy of chromium, cobalt and nickel. Not only is this alloy highly malleable, it is also impressively strong, with strength increasing as it cools.
When developing new structural materials, chemists often pay special attention to two characteristics ductility and strength . Usually you have to find a compromise between these two characteristics.
For example, although an iron plate can withstand a smaller load than a stone slab, the metal will bend and not lose integrity when deformed, and the stone will crack and fall into pieces.
The new alloy, studied by a group of American scientists, combines ductility and strength, and when cooled, both of these properties only increase.
The alloy was named CrCoNi, after the chemical symbols of its three metals: chromium , cobalt and nickel.
Unlike many other alloys, all three metals are included in CrCoNi in equal proportions, which, apparently, gives it its amazing properties.
The scientists tested the alloy’s toughness (its ability to absorb mechanical energy as it deforms under impact loading) at ultra-low temperatures, usually making even the best steels startlingly brittle.
It turned out that at a temperature of 20 kelvins, or minus 253 degrees Celsius, the impact strength of CrCoNi reached 500 megapascals per meter.
For comparison: under the same conditions, the impact strength of the aluminum body of a passenger aircraft is about 35 megapascals per meter, and some of the best steel grades are only about 100.
Researchers first started experimenting with CrCoNi and other alloys ten years ago.
At first they cooled them down to the temperature of liquid nitrogen (about 77 kelvins, or minus 193 degrees Celsius), but then, having discovered the impressive impact strength of the alloy, they continued cooling down to the temperature of liquid helium.
By studying the structure of the alloy under a microscope, the researchers realized that CrCoNi remains so strong due to changes in the structure of the crystal lattice , which eventually changes from cubic to hexagonal.
Unfortunately, the “superalloy” is unlikely to go into mass production: due to the high demand in the production of batteries, there is a global shortage of cobalt and nickel, so, most likely, CrCoNi will be used only for the manufacture of arctic equipment or spacecraft hulls.
Now the researchers want to find out whether it is possible to obtain an alloy of similar strength from cheaper materials, and warn that the real use of CrCoNi for the benefit of mankind is still very far away.
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