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Structure and mechanical properties of the AlNbTiVZr x (x = 0; 0.1; 0.25; 0.5; 1; 1.5) refractory high-entropy alloys were investigated after arc melting and annealing at 1200°C for 24 h. The AlNbTiV alloy had a B2 ordered single phase structure. Alloying with Zr resulted in (i) change of the degree of order of the B2 phase; and (ii) precipitation of the Zr 5 Al 3 and C14 Laves ZrAlV phases. The density of the AlNbTiVZr x alloys varied from 5590 kg m −3 for the AlNbTiV alloy to 5870 kg m −3 for the AlNbTiVZr 1.5 alloy. The compression yield strength at 22°C increased with an increase in the Zr content from 1000 MPa for the AlNbTiV alloy to 1535 MPa for the AlNbTiVZr 1.5 alloy. The plasticity raised from 6% for the AlNbTiV alloy to > 50% for the AlNbTiVZr 0.5 alloy and then dropped to 0.4% for the AlNbTiVZr 1.5 alloy. At 600°C, the strongest alloy was also the AlNbTiVZr 1.5 , whereas, at 800°C, the AlNbTiVZr 0.1 alloy demonstrated the maximum strength. The plasticity of the AlNbTiV alloy at 600°C increased up to 14.3%, while the Zr-containing alloys had lower plasticity. At 800°C, all the AlNbTiVZr x alloys could be plastically deformed up to 50% of strain without fracture. Ordering in the alloys and the reasons of a complicated dependence of mechanical properties of the AlNbTiVZr x alloys on the Zr content and temperature were discussed.

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a b s t r a c tMicrostructural evolution during cold sheet rolling to 80% thickness strain and annealing at 600e1100 C for 30 min of the CoCrFeNiMn high entropy alloy doped with 1 at.% of C and resulting mechanical properties of the alloy are reported. It is shown that in the initial homogenized (24 h at 1000 C) condition the alloy has single fcc phase structure. Cold rolling is accompanied by dislocation slip, deformation twinning and formation of shear bands. Annealing at 600 C after 80% cold rolling results only in partial recrystallization of cold-deformed structure, while an increase of the annealing temperature produces fully recrystallized microstructure. Comparison with the data on undoped CoCrFeNiMn alloy demonstrates that the addition of carbon pronouncedly increases dislocation activity simultaneously retarding deformation twinning during rolling and decreases the fraction of twin boundaries in the annealed condition. The effect of carbon can be attributed to an increase of stacking fault energy of the carbon-containing alloy. Cold rolling results in a substantial strengthening of the alloy; its ultimate tensile strength approaches 1500 MPa, but at the expense of low ductility. Good combination of strength and ductility can be obtained after annealing. For example, after annealing at 800 C, the alloy has yield strength of 720 MPa, ultimate tensile strength of 980 MPa, uniform elongation of 21% and elongation to fracture of 37%. It is shown that the high strength of the annealed alloy can be attributed to (i) strong grain boundary strengthening; (ii) solid solution strengthening by carbon.