According to metallurgists, the structure of a material defines its properties. But researchers have found an alloy with the simplest structure. Until you try to distort it. So its structure becomes more complex. And gives the alloy exceptional strength.
For one physicistphysicist, toughness is the ability of a material to resist the propagation of a crack. Precisely, physicists from Berkeley Lab (USA) have just measured the highest toughness ever measured on a material. A metal alloy of chromium, cobaltcobalt and nickel (CrCoNi). Even more surprisingly, this material is not only extreme ductileductile – understand malleable – and tough, but these properties improve at low temperatures. The opposite of what happens for most known materials.
Note that this strange alloy corresponds to what scientists call a high alloy. entropyentropy (HEA). It consists of an equal mixture of each of these elements. It is undoubtedly precisely this composition that gives it its character resistanceresistance. Specifically, the researchers identified the underlying reasons for the tremendous toughness of this alloy. On the side of linear defects in its crystalline structure, which tend to cause sliding on parallel planes and thus form kind of obstacles to the initial crack. If the applied force is increased further, the face-centered cubic arrangement breaks off atomsatoms chromium, cobalt and nickel form a compact hexagonal arrangement.
Not yet in the real world
These mechanisms are already known. But this is the first time they appear in one “magic sequence” leading to extraordinary properties. Berkeley Lab physicists measured the toughness of their alloy at about -250 °C – something like the temperature of helium liquidliquid — at about 500 MPa m1/2. In comparison, that ofaluminumaluminum employed in the manufacture of aircraft is of the order of 35 and the best of metalsmetals is between 100 and 200.
This type of alloy can be particularly useful in extreme conditions. As in the extremely cold temperatures of space. Because so far the manufacturing processes are still expensive. And the rare elements – the battery industry causes shortages of cobalt and nickel. The researchers hope to be able to replace them. But it probably won’t be tomorrow that we get to enjoy this most resistant material in the world.