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Entropy 2018, 20(7), 488; https://doi.org/10.3390/e20070488

The Effect of Scandium Ternary Intergrain Precipitates in Al-Containing High-Entropy Alloys

1
College of Engineering, Swansea University, Swansea SA1 8EN, Wales, UK
2
Faculty of Chemistry and Mineralogy, Institute for Mineralogy, Crystallography and Materials Science, Leipzig University, Scharnhorststr. 20, 04275 Leipzig, Germany
3
Institute of Solid State Chemistry, Pervomaiskaia str. 91, 620990 Ekaterinburg, Russia
*
Author to whom correspondence should be addressed.
Received: 4 June 2018 / Revised: 15 June 2018 / Accepted: 19 June 2018 / Published: 22 June 2018
(This article belongs to the Special Issue New Advances in High-Entropy Alloys)
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Abstract

We investigate the effect of alloying with scandium on microstructure, high-temperature phase stability, electron transport, and mechanical properties of the Al2CoCrFeNi, Al0.5CoCrCuFeNi, and AlCoCrCu0.5FeNi high-entropy alloys. Out of the three model alloys, Al2CoCrFeNi adopts a disordered CsCl structure type. Both of the six-component alloys contain a mixture of body-centered cubic (bcc) and face centered cubic (fcc) phases. The comparison between in situ high-temperature powder diffraction data and ex situ data from heat-treated samples highlights the presence of a reversible bcc to fcc transition. The precipitation of a MgZn2-type intermetallic phase along grain boundaries following scandium addition affects all systems differently, but especially enhances the properties of Al2CoCrFeNi. It causes grain refinement; hardness and electrical conductivity increases (up to 20% and 14% respectively) and affects the CsCl-type → fcc equilibrium by moving the transformation to sensibly higher temperatures. The maximum dimensionless thermoelectric figure of merit (ZT) of 0.014 is reached for Al2CoCrFeNi alloyed with 0.3 wt.% Sc at 650 °C. View Full-Text
Keywords: high-entropy alloys; in situ X-ray diffraction; grain refinement; thermoelectric properties; scandium effect high-entropy alloys; in situ X-ray diffraction; grain refinement; thermoelectric properties; scandium effect
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Riva, S.; Mehraban, S.; Lavery, N.P.; Schwarzmüller, S.; Oeckler, O.; Brown, S.G.R.; Yusenko, K.V. The Effect of Scandium Ternary Intergrain Precipitates in Al-Containing High-Entropy Alloys. Entropy 2018, 20, 488.

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