期刊
ACTA MATERIALIA
卷 146, 期 -, 页码 265-272出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2017.12.049
关键词
Magnesium alloy; Dislocation dissociation; Slip systems; Generalized stacking fault energy; Density-functional theory
资金
- National Key R&D Program of China [2017YFA0204403]
- NSFC [51722102, 21773120]
- Fundamental Research Funds for the Central Universities [30917011201]
- Jiangsu Key Laboratory of Advanced Micro Nano Materials and Technology
- US Army Research Office [W911 NF-17-1-0350]
- [NSF-CMMI-1631873]
- [NSF-CMMI-1437327]
Alloying magnesium (Mg) with rare earth elements such as yttrium (Y) has been reported to activate the pyramidal slip systems and improve the plasticity of Mg at room temperature. However, the origins of such dislocations and their dissociation mechanisms remain poorly understood. Here, we systematically investigate these mechanisms using dispersion-inclusive density-functional theory, in combination with molecular dynamics simulations. We find that dislocations form more readily on the pyramidal 1 plane than on the pyramidal II plane in Mg. The addition of Y atoms in Mg facilitates the dissociation of dislocations on pyramidal II, leading to the easier formation of the pyramidal 11 than pyramidal 1 in Mg-Y alloy. Importantly, in pyramidal II slip plane, a flat potential-energy surface (PES) exists around the position of stable stacking fault energy (SFE), which allows cooperative movement of atoms within the slip plane. Alloying Mg with Y atoms increases the range of the PES, and ultimately promotes different sliding pathways in the Mg-Y alloy. These findings are consistent with experimentally observed activation of the pyramidal II slip system in Mg-Y alloys, and provide important insight into the relationship between dislocation structure and macroscopic enhancement of plasticity. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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