Influence of Chromium on the Phase Composition and Specific Features of Hardening of the MnFeCoNiCu High-Entropy Alloy
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INFLUENCE OF CHROMIUM ON THE PHASE COMPOSITION AND SPECIFIC FEATURES OF HARDENING OF THE MnFeCoNiCu HIGH-ENTROPY ALLOY О. M. Myslyvchenko,1, 2 М. О. Krapivka,1 О. S. Tereshchenko,3 and М. I. Filep4 A six-component system of CoNiCuCrx high-entropy alloys with different contents of chromium (where x = 0, 0.5, 1.0, 2.0, and 3.0 mole) is obtained by the method of argon-arc melting in a МІFІ-9 study. By the methods of X-ray diffraction analysis, scanning-electron microscopy, and indentation, we investigate the influence of chromium on the crystalline structure, microstructure, and hardness of these alloys in the as-cast state. In their structure, depending on the chromium content, we detect a mixture of the following phase components: two face-centered cubes + a body-centered cube + an intermetallic σ -phase (FCC1 + FCC2 + BCC + σ ). It is also established that, as the chromium content increases, we observe the formation of the bcc structure and the σ -phase, which is the predominant factor of hardening of the alloy. Keywords: high-entropy alloys, phase composition, hardness.
Introduction Most alloys currently used in industry were developed on the basis of a single main element (metal), namely, Fe, Al, Cu, Ti, etc. A new class of alloys was created in [1]. These alloys were called high-entropy alloys (HEA) due to theirs high entropy of mixing in the liquid state as compared with traditional alloys. By definition, any HEA must have at least five components with a concentration of each component varying within the range 5–35 at.%. For some compositions, these alloys may have high characteristics of hardness, wear resistance, oxidation resistance, and corrosion resistance [2, 3]. During the last decade, high-entropy alloys of different compositions were obtained and investigated. Among them, we can especially mention a single-phase fcc MnFeCoNiCu alloy, which has been sufficiently well investigated and exhibits high strength and thermally stable mechanical properties [4, 5]. The aim of the present work is to study the influence of chromium on the structure, phase composition, and hardness of the MnFeCoNiCu HEA. This choice is determined by the fact that chromium is a relatively low-cost metal, which is commonly used as an alloying element in the compositions of steels and, moreover, according to the binary diagrams of state, may form the σ-phase with several components of the alloy. Procedure The alloys were obtained in a МІFІ-9 argon-arc furnace in the atmosphere of high-purity argon. The procedure of melting was performed with a nonconsumable tungsten electrode on a copper water-cooled hearth. 1 2 3 4
Frantsevych Institute for Problems in Materials Science, National Academy of Sciences of Ukraine, Kyiv, Ukraine. Corresponding author; e-mail: [email protected]. “MATERIALS LAB," LLC, Kyiv, Ukraine.
Research Institute of Solid-State Physics and Chemistry, Uzhhorod National University, Uzhhorod, Ukraine.
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 56, No. 3, pp. 81–85, May–June, 2020. Original article s
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