Early stage phase separation of AlCoCr0.75Cu0.5FeNi high-entropy powder at the nanoscale

Peter, Nicolas J and Duarte, Maria J and Liebscher, Christian H and Srivastava, V C and Uhlenwinkel, Volker and Jägle, Eric A and Dehm, Gerhard (2020) Early stage phase separation of AlCoCr0.75Cu0.5FeNi high-entropy powder at the nanoscale. Journal of Alloys and Compounds, 820 . p. 153149.

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High entropy alloys are generally considered to be single phase material. This state is, however, typically a non-equilibrium state after fabrication at high cooling rates. Phase constitution after fabrication or heat treatment is mostly known for isothermal annealing only and for casts as well as rapidly quenched alloys. Knowledge on early phase separation stages of high entropy alloys and their mechanisms are missing so far. Here, we present results on phase separation at intermediate cooling rates, by characterization of gas atomized powder of the AlCoCr0.75Cu0.5FeNi alloy. Although investigation by X-ray diffraction and Electron Backscatter Diffraction indicates a single-phase nature of the powder particles, aberration-corrected scanning transmission electron microscopy and atom probe tomography reveal a nanoscale phase separation into Ni–Al-rich B2 and Fe–Cr-rich A2 regions as well as a high number density of 3.1 × 1024 Cu-rich clusters per m3 in the B2 matrix. The observed phase separation and cluster formation are linked to spinodal decomposition and nucleation processes, respectively. The study highlights that adequate characterization techniques need to be chosen when making statements about phase stability and structural evolution in compositionally complex alloys.

Item Type:Article
Official URL/DOI:https://www.sciencedirect.com/science/article/pii/...
Uncontrolled Keywords:High entropy alloys; Microstructure; 3D-characterization; Phase composition; Spinodal decomposition
Divisions:Material Science and Technology
ID Code:8294
Deposited By:Dr. A K Sahu
Deposited On:09 Feb 2021 15:12
Last Modified:09 Feb 2021 15:12
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