Nanoscale phase separation in a fcc-based CoCrCuFeNiAl0.5 high-entropy alloy
Journal article, 2015

Nano-scale phase separation is reported in a nominal single-phase, high-entropy alloy (HEA), which was characterized using scanning transmission electron microscopy (STEM) combined with atom probe tomography (APT). Despite the fact that X-ray diffraction exhibits a single face-centered-cubic (fcc) phase feature of the as-cast alloy prepared by melt spinning, selected area electron diffraction reveals weak L12 ordering in the as-spun alloy. High-resolution STEM shows the presence of two coherent nanophases with distinct L12 and fcc structures, coupling with compositional segregations. The ordering of the L12 domains is enhanced after annealing at 500 °C. Electron energy loss spectroscopy and APT analyses reveal that the L12 nano-phase is enriched with Fe, Co, Cr and Ni, while the fcc domains are a Cu-rich phase. The nano-scale phase separation can effectively minimize the lattice distortions caused by the atomic size difference in the constituent elements, which may offer structural insights into the unusual mechanical behavior and phase stability of fcc HEA.

Atom probe tomography

Phase separation

Lattice distortion

High-entropy alloy

Cs-corrected TEM


X. Xu

Tohoku University

P. Liu

Tohoku University

Sheng Guo

Chalmers, Materials and Manufacturing Technology, Surface and Microstructure Engineering

A. Hirata

Tohoku University

T. Fujita

Tohoku University

T. Nieh

University of Tennessee

C.T. Liu

City University of Hong Kong

M. Chen

Shanghai Jiao Tong University

Tohoku University

Acta Materialia

1359-6454 (ISSN)

Vol. 84 145-152

Subject Categories

Metallurgy and Metallic Materials

Areas of Advance

Materials Science



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