Abstract
We report the mechanical and microstructural characteristics of a medium-entropy alloy, Co17.5Cr12.5Fe55Ni10Mo5 (atomic percent, at%) at cryogenic temperatures, down to a record low temperature of 0.5 K. The alloy exhibits excellent strength and ductility combined with a high strain-hardening rate in the entire temperature range investigated. Its property profile, including the yield strength, ultimate tensile strength, strain hardening capability, and absorbed mechanical energy, is better than those of most alloys and HEAs used in cryogenics. Within the interval of extremely low temperatures considered (0.5–4.2 K), the alloy exhibits several unusual features, including anomalies of the temperature dependence of the yield strength and tensile ductility, discontinuous plastic deformation (DPF), and a change in the propensity for the deformation-induced martensitic transformation. While the occurrence of these effects in the same temperature interval may be fortuitous, we hypothesize that they are interrelated and provide a tentative explanation of the observed phenomena on this basis.
Original language | English |
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Pages (from-to) | 55-68 |
Number of pages | 14 |
Journal | Materials Today |
Volume | 50 |
DOIs | |
State | Published - Nov 2021 |
Externally published | Yes |
Funding
We are most grateful to the Editor and Reviewers for their excellent comments. The present work was supported by the Korea-Ukraine Bilateral Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and Information and Communication Technology (ICT) [NRF- 2018K1A3A1A13087775 ]. The research was also supported by (1) the Future Materials Discovery Program through the NRF funded by the Ministry of Science and ICT [ NRF-2016M3D1A1023384 ], and (2) the NRF grant funded by the Korea government (MSIP) [ NRF-2021R1A2C3006662 ]. P. K. L. acknowledges the support from (1) the U.S. Army Office Project [W911NF-13-1-0438 and W911NF-19-2-0049] with the program managers, Drs. Michael P. Bakas, David M. Stepp, and S. Mathaudhu, and (2) the National Science Foundation [DMR-1611180 and 1809640] with the program directors, Drs. Judith Yang, Gary Shiflet, and Diana Farkas.
Keywords
- Cryogenic temperatures
- Discontinuous plastic deformation
- Dislocation
- Martensitic phase transformation
- Medium-entropy alloy