期刊
出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2021.141446
关键词
High-entropy alloys; Dislocation; Stacking fault; Phase transformation; Mechanical properties
类别
资金
- Special Fund for Research on National Major Research Instrument [51927801]
- National Key Research and Development Program of China [2017YFA0403803, 2019YFA0209901, 2018YFA0702901]
- fund of the State Key Laboratory of Solidification Processing in NWPU [SKLSP201902]
- Liao Ning Revitalization Talents Program [XLYC1807047]
- Fund of Science and Technology on Reactor Fuel and Materials Laboratory [STRFML-2020-04]
- U.S. National Science Foundation [DMR-1611180, 1809640]
- Army Office Project [W911NF-13-1-0438, W911NF-19-2-0049]
The non-equiatomic Co29Cr29Fe29Ni12.5W0.5 high-entropy alloy exhibited exceptional strength-ductility synergy at cryogenic temperatures, with significant increase in yield strength and outstanding ductility. The microstructure transformed to a hexagonal-close packed phase at low temperatures, contributing to the high mechanical properties observed.
A non-equiatomic Co29Cr29Fe29Ni12.5W0.5 high-entropy alloy (HEA) strengthened by two-step rolling was fabricated, and its microstructure evolution and tensile behavior at cryogenic temperatures were investigated. When the temperature decreases from 293 K to 173 K, the yield strength increases from 640 MPa to 1017 MPa. At 77 K, an outstanding strength-ductility synergy can be observed, with a yield strength of 1.33 GPa and an excellent ductility of 46%. Prior to tensile testing, the annealed alloy largely has a single face-centered cubic (FCC) structure, while a hexagonal-close packed (HCP) phase is formed in the cryogenically tensile-fractured alloy along the {111} planes. Such high yield strength and tensile plasticity values at cryogenic temperatures are extremely rare in HEAs and even in metal alloys. The deformation micro-mechanism was carefully investigated by a transmission electron microscope, and the results indicated that the cryogenic-temperature properties could be attributed to stacking faults (SFs) and the phase having a hexagonal-close-packed (HCP) structure. The densities of the SFs and the HCP laths have a considerable influence on the work-hardening behavior.
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