Evolution of Microstructure and Mechanical Properties of a CoCrFeMnNi High-Entropy Alloy during High-Pressure Torsion at Room and Cryogenic Temperatures
Abstract
:1. Introduction
2. Materials and Methods
3. Results
4. Discussion
5. Conclusions
- (1)
- HPT processing at room temperature results in the formation of in inhomogeneous severely deformed microstructure with (sub)grains of ~50 nm already after the rotation for 180°. The microstructure evolution was associated with intensive deformation-induced twinning, and substructure development resulted in a gradual microstructure refinement.
- (2)
- HPT at 77 K produced more heterogeneous structure in comparison with the room-temperature deformation. The dislocation density was much higher after cryogenic deformation.
- (3)
- Tensile strength of the alloy after HPT at 293 K was found to be strongly dependent on HPT strain. The ultimate tensile strength increased from 981 to 2069 MPa when the rotation angle at HPT increased from 90° to 720°. In all examined conditions, the alloy exhibited limited ductility.
- (4)
- A decrease of HPT temperature from 293 to 77 K resulted in higher tensile strength. A rotation for 180° resulted in the ultimate tensile strength of 1193 MPa and 1596 MPa after processing at room and cryogenic temperature, respectively.
- (5)
- An increase of yield strength of the alloy with an increase of the angle of rotation can mostly be ascribed to a contribution of Hall–Petch strengthening. In turn, higher strength of the alloy after HPT at 77 K was attributed to substructure (dislocation) hardening.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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HPT Condition | YS, MPa | UTS, MPa | UE, % | TE, % | |
---|---|---|---|---|---|
Temperature, K | Rotation, ° | ||||
293 | 90 | 860 | 981 | 1.4 | 11.9 |
180 | 1134 | 1197 | 0.5 | 6.4 | |
720 | 1834 | 2069 | 1.4 | 7.4 | |
77 | 180 | 1442 | 1596 | 1.3 | 10.4 |
Strain, ° (Temperature, K) | Dislocation Density, m−2 | Calculated Grain Size, nm | σH−P, MPa | σρ, MPa | Predicted YS, MPa |
---|---|---|---|---|---|
90 (293) | 1.48 × 1015 | 2500 | 311 | 475 | 911 |
180 (293) | 9.14 × 1014 | 580 | 646 | 373 | 1144 |
720 (293) | 8.86 × 1014 | 140 | 1317 | 367 | 1809 |
180 (77) | 2.9 × 1015 | 625 | 625 | 664 | 1414 |
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Zherebtsov, S.; Stepanov, N.; Ivanisenko, Y.; Shaysultanov, D.; Yurchenko, N.; Klimova, M.; Salishchev, G. Evolution of Microstructure and Mechanical Properties of a CoCrFeMnNi High-Entropy Alloy during High-Pressure Torsion at Room and Cryogenic Temperatures. Metals 2018, 8, 123. https://doi.org/10.3390/met8020123
Zherebtsov S, Stepanov N, Ivanisenko Y, Shaysultanov D, Yurchenko N, Klimova M, Salishchev G. Evolution of Microstructure and Mechanical Properties of a CoCrFeMnNi High-Entropy Alloy during High-Pressure Torsion at Room and Cryogenic Temperatures. Metals. 2018; 8(2):123. https://doi.org/10.3390/met8020123
Chicago/Turabian StyleZherebtsov, Sergey, Nikita Stepanov, Yulia Ivanisenko, Dmitry Shaysultanov, Nikita Yurchenko, Margarita Klimova, and Gennady Salishchev. 2018. "Evolution of Microstructure and Mechanical Properties of a CoCrFeMnNi High-Entropy Alloy during High-Pressure Torsion at Room and Cryogenic Temperatures" Metals 8, no. 2: 123. https://doi.org/10.3390/met8020123
APA StyleZherebtsov, S., Stepanov, N., Ivanisenko, Y., Shaysultanov, D., Yurchenko, N., Klimova, M., & Salishchev, G. (2018). Evolution of Microstructure and Mechanical Properties of a CoCrFeMnNi High-Entropy Alloy during High-Pressure Torsion at Room and Cryogenic Temperatures. Metals, 8(2), 123. https://doi.org/10.3390/met8020123