AUTHOR=Röhrens Daniel , Navaeilavasani Niloofar , Stryzhyboroda Oleg , Swientek Fabian , Pavlov Paul , Meister Dirk , Genau Amber , Hecht Ulrike 

TITLE=Microstructure and Mechanical Properties of BCC-FCC Eutectics in Ternary, Quaternary and Quinary Alloys From the Al-Co-Cr-Fe-Ni System

JOURNAL=Frontiers in Materials

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.567793

DOI=10.3389/fmats.2020.567793

ISSN=2296-8016

ABSTRACT=<p>This study aimed at understanding the structure and properties of dual-phase eutectics in ternary, quaternary, and quinary alloys of the Al-Co-Cr-Fe-Ni system. The alloys at case were i) Ni<sub>48</sub>Fe<sub>34</sub>Al<sub>18</sub>, ii) Ni<sub>44</sub>Fe<sub>20</sub>Cr<sub>20</sub>Al<sub>16,</sub> and iii) Ni<sub>34.4</sub>Fe<sub>16.4</sub>Co<sub>16.4</sub>Cr<sub>16.4</sub>Al<sub>16.4</sub>. Samples in the form of cylindrical bars, diameter 10 mm × 150 mm, were produced by arc melting and suction casting from pure elements (&gt;99.9 wt%). Bridgman solidification at low growth velocity was used to produce additional samples with large eutectic spacing and lamellae thickness of the two phases body-centered cubic (BCC)-B2 and face-centered cubic (FCC) in order to facilitate phase characterization by energy-dispersive X-ray analysis (scanning electron microscopy/energy-dispersive spectroscopy) and nano-indentation. In agreement with thermodynamic calculations, each of the phases was found to be multi-component and contain all alloying elements in distinct amounts. The mechanical properties of the individual phases were analyzed in relation to their composition using nano-indentation experiments. These measurements revealed some insights into “high-entropy effects” and their contribution to the elastoplastic response to indentation loading. Further analysis focused on as-cast as well as heat-treated samples comprising phase fraction measurements, micro-indentation, and miniature testing in three-point bending configuration. For optimum heat treatment conditions, a good balance of strength and ductility was obtained for each of the investigated alloys. Further work is necessary in order to assess their capability as structural materials.</p>