Local chemical ordering in CoCrNi medium-entropy alloy (MEA) was directly observed by the use of atom probe tomography. It was found that the densities of Cr, Co, and Ni were almost the same along the [111] direction, while those along the [001] direction were modulated to take a slightly enhanced and depleted value alternately within approximately 10 atomic layers corresponding to about 2 nm. The degree of modulation of Co and Ni was stronger than that of Cr. It was suggested that Cr-rich {001} atomic layers and (Ni + Co)-rich {001} layers tended to align mutually in the face-centered-cubic CoCrNi solid solution alloy. The mechanical properties of the MEA was found not to be affected by the presence of the local chemical ordering.

• Received 28 April 2021
• Revised 23 July 2021
• Accepted 11 August 2021

DOI:https://doi.org/10.1103/PhysRevMaterials.5.085007