High pressure synthesis of a hexagonal close-packed phase of the high-entropy alloy CrMnFeCoNi

摘要

High-entropy alloys, near-equiatomic solid solutions of five or moreelements, represent a new strategy for the design of materials with propertiessuperior to those of conventional alloys. However, their phase space remainsconstrained, with transition metal high-entropy alloys exhibiting only face- orbody-centered cubic structures. Here, we report the high-pressure synthesis ofa hexagonal close-packed phase of the prototypical high-entropy alloyCrMnFeCoNi. This martensitic transformation begins at 14 GPa and is attributedto suppression of the local magnetic moments, destabilizing the initial fccstructure. Similar to fcc-to-hcp transformations in Al and the noble gases, thetransformation is sluggish, occurring over a range of >40 GPa. However, thebehaviour of CrMnFeCoNi is unique in that the hcp phase is retained followingdecompression to ambient pressure, yielding metastable fcc-hcp mixtures. Thisdemonstrates a means of tuning the structures and properties of high-entropyalloys in a manner not achievable by conventional processing techniques.