Nature Communications
Nature Communications
5 years ago

Polymorphism in a high-entropy alloy

Polymorphism in a high-entropy alloy
Vitali B. Prakapenka, John S. Okasinski, Eran Greenberg, Yong Liu, Yuan Wu, Yang Ren, Zhaoping Lu, Fei Zhang, Hongbo Lou, Jinyuan Yan, Zhidan Zeng, Qiaoshi Zeng, Xiongjun Liu
Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiation X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. As pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.

Publisher URL: http://www.nature.com/articles/ncomms15687

DOI: 10.1038/ncomms15687

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