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The temperature dependence of the mechanical properties of the CoCrFeNi medium-entropy alloy (MEA) manufactured by laser-directed energy deposition (L-DED) and additionally annealed at 1200 °C for 24 h was studied. The microstructure of the as-deposited alloy was represented by a single-phase face-centered cubic structure with coarse columnar grains and a high density of dislocation. Annealing resulted in the development of recrystallization and a reduction in dislocation density. The CoCrFeNi alloy produced by L-DED demonstrated mechanical properties comparable with those of the fine-grained equiatomic CoCrFeMnNi alloy, produced by casting followed by thermomechanical processing. Namely, as-deposited CoCrFeNi had a yield strength (YS) and ultimate tensile strength (UTS) of YS = 370 MPa and UTS = 610 MPa at room temperature, and YS = 565 MPa and UTS = 965 MPa at cryogenic temperature, along with a ductility of ~60%. Annealing resulted in a decrease in strength to YS = 180/350 MPa at 293/77 K. A quantitative analysis of various strengthening mechanisms showed that some strength increment of the as-deposited alloy was ensured by the high dislocation density formed during L-DED.
Details
Medium entropy alloys;
Columnar structure;
Investigations;
Deposition;
Grain boundaries;
Thermomechanical treatment;
Room temperature;
Recrystallization;
Dislocation density;
Scientific imaging;
Energy;
Grain size;
Microstructure;
Entropy;
Annealing;
Solid solutions;
Temperature dependence;
Grain growth;
Ultimate tensile strength;
Cryogenic temperature;
Lasers;
Thermomechanical properties;
Temperature;
Ductility;
Deformation;
Alloys;
Yield strength
; Astakhov, Ilya 1
; Kovalenko, Ekaterina 2
; Kochura, Elizaveta 2 ; Semenyuk, Anastasia 1
; Zherebtsov, Sergey 1
; Klimova-Korsmik, Olga 2 ; Stepanov, Nikita 1
1 World-Class Research Center, “Advanced Digital Technologies”, Saint Petersburg State Marine Technical University, 190121 Saint Petersburg, Russia;
2 World-Class Research Center, “Advanced Digital Technologies”, Saint Petersburg State Marine Technical University, 190121 Saint Petersburg, Russia;