AlCoCrCuFeNi-Based High-Entropy Alloys: Correlation Between Molar Density and Enthalpy of Mixing in the Liquid State
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RODUCTION
CONVENTIONAL alloys are mainly based on one principal element with different kinds of alloying elements added to improve their properties. These alloys form an alloy family based on the chosen principal element. However, the number of elements in the periodic table is limited, and thus the alloy families, which can be developed, are also limited. The new concept, first proposed in 1995, has been named a high-entropy alloy (HEA).[1,2] According to proposed definition, any multi-component alloy consisting of five or more principal elements, which have a concentration between 5 and 35 at. pct, belongs to the HEA family. Besides principal elements, HEAs could contain also minor elements with concentrations below 5 at. pct.
YURIY PLEVACHUK is with the Department of Metal Physics, Ivan Franko National University of Lviv, 79005 Lviv, Ukraine. Contact e-mail: [email protected] JU¨RGEN BRILLO is with the Institut fu¨r Materialphysik im Weltraum, Deutsches Zentrum fu¨r Luft- und Raumfahrt (DLR), 51170 Cologne, Germany. ANDRIY YAKYMOVYCH is with the Department of Metal Physics, Ivan Franko National University of Lviv and also with the Department of Inorganic Chemistry – Functional Materials, Faculty of Chemistry, University of Vienna, 1090 Vienna, Austria. Contact e-mail: [email protected] Manuscript submitted March 6, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
Compared to conventional alloys, these alloys have significantly higher mixing entropies, which lead to the formation of liquid or random solid solution states.[3,4] Thus, the effect of entropy is much more pronounced in HEAs than in conventional alloys. According to the Gibbs phase rule, a system of i components could contain maximum (i + 1) phases in the equilibrium state. The experimental results published in References 4 and 5 show that the high entropy of mixing in these alloys facilitates the formation of solid solution phases with simple structures. Thus, it reduces the number of phases formed in HEAs during solidification process. Such unique structural features caused by the effect of higher entropy are of paramount importance for further industrial application of these alloys.[6] Due to the unique multi-principal element composition, HEAs can possess extraordinary properties, including high strength/hardness, outstanding wear resistance, exceptional high-temperature strength, good structural stability, good corrosion, and oxidation resistance. Some of these properties are not seen in conventional alloys, making HEAs attractive in many fields. The fact that it can be used at high temperatures broadens its spectrum of applications even further. Moreover, a fabrication of HEAs does not require special processing techniques or equipment, which indicates that the mass production of HEAs can be easily implemented with existing equipment and technologies. According to Reference 4, more than 300 HEAs have been reported, which were prepared from more than 30 various elements. Based on the above
mentioned, we have a new rapidly developing c
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