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Materials 2018, 11(2), 175; https://doi.org/10.3390/ma11020175

Microstructural Evolution and Phase Formation in 2nd-Generation Refractory-Based High Entropy Alloys

1
Israel Institute of Metals, Haifa 3200003, Israel
2
Institute of Metals Physics Ural Branch of RAS, 620041 Ekaterinburg, Russia
*
Author to whom correspondence should be addressed.
Received: 27 December 2017 / Revised: 16 January 2018 / Accepted: 22 January 2018 / Published: 23 January 2018
(This article belongs to the Special Issue High Entropy Alloys)
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Abstract

Refractory-based high entropy alloys (HEAs) of the 2nd-generation type are new intensively-studied materials with a high potential for structural high-temperature applications. This paper presents investigation results on microstructural evolution and phase formation in as-cast and subsequently heat-treated HEAs at various temperature-time regimes. Microstructural examination was performed by means of scanning electron microscopy (SEM) combined with the energy dispersive spectroscopy (EDS) mode of electron probe microanalysis (EPMA) and qualitative X-ray diffraction (XRD). The primary evolutionary trend observed was the tendency of Zr to gradually segregate as the temperature rises, while all the other elements eventually dissolve in the BCC solid solution phase once the onset of Laves phase complex decomposition is reached. The performed thermodynamic modelling was based on the Calculation of Phase Diagrams method (CALPHAD). The BCC A2 solid solution phase is predicted by the model to contain increasing amounts of Cr as the temperature rises, which is in perfect agreement with the actual results obtained by SEM. However, the model was not able to predict the existence of the Zr-rich phase or the tendency of Zr to segregate and form its own solid solution—most likely as a result of the Zr segregation trend not being an equilibrium phenomenon. View Full-Text
Keywords: high-entropy; refractory; thermodynamics; solid solution; intermetallic phase high-entropy; refractory; thermodynamics; solid solution; intermetallic phase
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Eshed, E.; Larianovsky, N.; Kovalevsky, A.; Popov Jr., V.; Gorbachev, I.; Popov, V.; Katz-Demyanetz, A. Microstructural Evolution and Phase Formation in 2nd-Generation Refractory-Based High Entropy Alloys. Materials 2018, 11, 175.

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