Thermal and Oxidation Behavior of CoCrFeMnNi Alloy with and Without Yttrium Oxide Particle Dispersion
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The equiatomic CoCrFeMnNi alloy is currently one of the most studied high-entropy alloys. In our previous work, a new grade of CoCrFeMnNi high-entropy alloy with yttria-based particle dispersion was introduced showing improved mechanical properties, especially high-temperature strength and creep rate. In this study, a detailed analysis of room to high-temperature thermal properties was performed, as it is important for defining the future application of the alloy and opening the discussion on tailoring the thermal response. Thermal properties are not well known for the original CoCrFeMnNi alloy or for CoCrFeMnNi with yttria dispersion. As a result of the analysis, thermal properties of both alloys and the effect of the oxide dispersion are discussed. Most of the thermal properties remain unchanged. However, it was found that the presence of 0.3% yttria influences the oxidation rate of CoCrFeMnNi alloy at the initial and intermediate oxidation times. The onset of the oxidation is described in detail. Yttria nano-oxide dispersion and related grain refinement also reduce the microstructural degradation caused by the formation of voids due to outward Mn diffusion.
Keywordshigh-entropy alloys oxidation particle dispersion thermal conductivity thermal expansion thermal properties
This work was financially supported by Czech Science Foundation through project no. 17-23964S and partially supported by the Czech Academy of Sciences within the New materials program of the Strategy AV21. The authors would like to acknowledge prof. RNDr. Antonín Dlouhý, CSc. for TEM analysis and Ing. Pavla Roupcová, Ph.D. for XRD analysis.
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