Влияние температур ы интенсивной пластической деформации на механические свойства высокоэнтропийного сплава CoCrFeNiMn

Yuriy O. Shapovalov, Elena D. Tabachnikova, Mikhail A. Tikhonovsky, A.V. Levenets , Michael Zehetbauer, Erhard Schafler

High entropy alloy (HEA) CoCrFeNiMn was produced by arc melting of the components in high-purity argon atmosphere withconsequent multiple homogenization annealing. The disc-shaped samples with diameter 10 mm and thickness of ~ 1 mm were producedfrom the ingots obtained. These samples were subjected to severe plastic deformation by high pressure torsion (HPT) in Bridgmananvil at a hydrostatic pressure of 6 GPa and at temperature 77 K. Plungers have been rotated for 5 times at a speed of 0.2 rot/min thatallows to produce uniform nanocrystalline structural state with average grain size of less than 100 nm. Mechanical tests have beenprovided under conditions of uniaxial compression of rectangular samples with size 1.3×0.6×0.6 mm3. The samples were cut from thediscs after HPT at a distance of 3 mm form disc centre. The analysis of stress-strain curves have been made in the temperature rangeof 300-4.2 K for the obtained nanostructured state. It was found that yield stress value monotonically increasing from 1.44 GPa to 2.48GPa while the temperature decrease from 300 K to 4.2 K, which is typical for thermally activated character of plastic deformation.Anomalous decrease in yield strength values in comparison with the same values for nanostructured HEA after HPT at 300 K wasestablished in all the temperature range (300-4.2 K) for the structural state after HPT at 77 K.The conducted analysis have been shown that the observed anomalous behaviour of yield strength during active deformation is conditioned by peculiarities of microsturcture appearing after cryodeformation by HPT at 77 K, in particular by formation of martensite phase with hcp lattice and connected with this decrease in dislocation density. It was shown that peculiarities of microstructure after HPT at 77 K effect considerably not only on strength of the alloy in local areas, i.e. its microhardness value, but also on the acting stresses responsible for the plastic deformation process under conditions of active deformation of nanocrystalline HEA CoCrFeMnNi.

Physics of Nanostructured Materials
External organisation(s)
National Science Center Kharkiv Institute of Physics and Technology (KIPT), National Academy of Sciences of Ukraine (NASU)
Вісник Харківського національного університету імені В. Н. Каразіна Серія : Фізика = Kharkov University bulletin
No. of pages
Publication date
Austrian Fields of Science 2012
103018 Materials physics
Portal url