Effect of thermomechanical processing on microstructure and mechanical properties of the carbon-containing CoCrFeNiMn high entropy alloy

JOURNAL OF ALLOYS AND COMPOUNDS

卷:693

Article

Stepanov, N. D.¹  Shaysultanov, D. G.¹  Chernichenko, R. S.¹  Yurchenko, N. Yu¹  Zherebtsov, S. V.¹  Tikhonovsky, M. A.²  Salishchev, G. A.¹ 

[1] Belgorod State Univ, Lab Bulk Nanostruct Mat, Pobeda 85, Belgorod 308015, Russia

[2] NAS Ukraine, Natl Sci Ctr, Kharkov Inst Phys & Technol, UA-61108 Kharkov, Ukraine

关键词: High entropy alloys;    Carbon;    Microstructure;    Thermomechanical processing;    Mechanical properties;   

DOI  :  10.1016/j.jallcom.2016.09.208

来源: Elsevier

【 摘 要 】

Microstructural evolution during cold sheet rolling to 80% thickness strain and annealing at 600-1100 degrees 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 degrees 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 degrees 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 degrees 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. (C) 2016 Elsevier B.V. All rights reserved.

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