INFLUENCE OF COMPOSITION AND MICROSTRUCTURE ON THE FEATURES OF MECHANICAL PROPERTIES OF Co-Cr-Fe-Mn-Ni HIGH ENTROPY ALLOYS

doi:10.26565/2312-4334-2017-1-06

A. V. Levenets Department of Physics and Technology, V.N. Karazin Kharkiv National University Svobody Sq.4, 61022 Kharkiv, Ukraine https://orcid.org/0000-0003-2102-3482
I. V. Kolodiy NSC «Kharkiv Institute of Physics and Technology»,Academicheskaya Str.1, 61108 Kharkiv, Ukraine https://orcid.org/0000-0001-8598-9732
N. V. Berezhnaya NSC «Kharkiv Institute of Physics and Technology», Academicheskaya Str.1, 61108 Kharkiv, Ukraine
Y. S. Lipovskaya NSC «Kharkiv Institute of Physics and Technology», Academicheskaya Str.1, 61108 Kharkiv, Ukraine

DOI: https://doi.org/10.26565/2312-4334-2017-1-06

Keywords: high-entropy alloys, Co-Cr-Fe-Mn-Ni alloys, stacking-fault energy, mechanical properties, deformation mechanism

Abstract

The structure and mechanical properties of high-entropy CoCrFeMnNi (equiatomic) and Co20Cr26Fe20Mn20Ni14 alloys, which differ significantly in the stacking-fault energy, are studied. The structure of the alloys was investigated in three states – as-cast, after homogenizing annealing at T = 1000 °C for 24h and after annealing at T = 850 °C. It was found that in the cast state and after homogenizing annealing at 1000 °C both alloys are single-phase solid solutions with a FCC lattice. Annealing at 850 °C preserves the single-phase state in the equiatomic CoCrFeMnNi alloy, but leads to the appearance of a σ-phase in the Co20Cr26Fe20Mn20Ni14 alloy. The mechanical properties of these alloys were studied in a single-phase state by uniaxial compression tests and hardness measurements. It was discovered, that both alloys in a single-phase state had high plasticity and tendency to force strain hardening. The behavior of hardening coefficients in the area of true strains e = 0.05 – 0.17 vary considerably. This may be due to a significant difference in the stacking-fault energy of the investigated alloys. As a result, in Co20Cr26Fe20Mn20Ni14 alloy along with dislocation deformation mechanism there is a high probability of implementation the twinning mechanism.

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