A new concept in metallic alloy design – called “high‐entropy alloys” – has yielded a multiple-element material that not only tests out as one of the toughest on record, but, unlike most materials, the toughness as well as the strength and ductility of this alloy actually improves at cryogenic temperatures. This multi-element alloy was synthesized and tested through a collaboration of researchers at the U.S. Department of Energy (DOE)’s Lawrence Berkeley and Oak Ridge National Laboratories (Berkeley Lab and ORNL).
“We examined CrMnFeCoNi, a high‐entropy alloy that contains five major elements rather than one dominant one,” says Robert Ritchie, a materials scientist with Berkeley Lab’s Materials Sciences Division. “Our tests showed that despite containing multiple elements with different crystal structures, this alloy crystalizes as a single phase, face‐centered cubic solid with exceptional damage tolerance, tensile strength above one gigapascal, and fracture toughness values that are off the charts, exceeding that of virtually all other metallic alloys.”
“High‐entropy alloys represent a radical departure from tradition,” Ritchie says, “in that they do not derive their properties from a single dominant constituent or from a second phase. The idea behind this concept is that configurational entropy increases with the number of alloying elements, counteracting the propensity for compound formation and stabilizing these alloys into a single phase like a pure metal.”