期刊
ACTA MATERIALIA
卷 199, 期 -, 页码 352-369出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2020.08.044
关键词
Lattice distortion; Chemical short-range order; Deformation; Medium entropy alloy
资金
- Office of Naval Research [N000141712810]
- Elings Prize Fellowship in Science by the California NanoSystems Institute on the UC Santa Barbara campus
- Office of Naval Research under contract ONR BRC Grant [N00014-18-1-2392]
- National Science Foundation [CNS-1725797]
- CNSI
- Materials Research Science and Engineering Center (MRSEC) at UC Santa Barbara [NSF DMR 1720256]
- National Science Foundation for Distinguished Young Scholars of China [11925203]
- Natural Science Foundation of China [11672110]
- U.S. Department of Defense (DOD) [N000141712810] Funding Source: U.S. Department of Defense (DOD)
As the numbers of medium- to high-entropy alloys being studied and impressive structural properties they exhibit increase rapidly, questions regarding the role played by their complex chemical fluctuations rise concomitantly. Here, using a combination of large-scale molecular dynamics (MD), a hybrid MD and Monte-Carlo simulation method, and crystal defect analysis, we investigate the role lattice distortion (LD) and chemical short-range order (CSRO) play in the nucleation and evolution of dislocations and nanotwins with straining in single crystal and nanocrystalline CoCrNi, a medium entropy alloy (MEA). LD and CSRO effects are elucidated by comparisons with responses from a hypothetical pure A-atom alloy, which bears the same bulk properties of the nominal MEA but no LD and no CSRO. The analysis reveals that yield strengths are determined by the strain to nucleate Shockley partial dislocations, and LD lowers this strain, while higher degrees of CSRO increase it. We show that while these partials prefer to nucleate in the CoCr clusters, regardless of their size, they find it increasingly difficult to propagate away from these sites as the level of CSRO increases. After yield, nanotwin nucleation occurs via reactions of mobile Shockley partials and is promoted in MEAs, due to the enhanced glide resistance resulting from LD and CSRO. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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