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First-Principles Study of Mechanical and Electronic Properties of η and η' Phases Present in 7xxx Alloys

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Abstract

The η' and η strengthening precipitates in Al–Zn–Mg alloys were investigated by the first principle calculations. Results of the heat of formation and cohesive energy indicates that the model of η′ with \(P{{\bar {6}}}\) and space group of No. 174 is the energy favored model. The structure, elastic constants and electronic properties of the energy favored η′ and η (MgZn2) were compared and discussed. The obtained negative heat of formation and cohesive energy indicates that both η′ and MgZn2 have good alloying ability and structural stability, while MgZn2 particles exhibit a higher structural stability compared to η′, for MgZn2 has a lower density of states (DOS) at the Fermi level, which was verified by the experiments that η′ is not as stable as MgZn2. In addition, the obtained elastic constants Cij of MgZn2 and η′ were calculated, from which were derived the elastic modulus such as bulk modulus (B), shear modulus (G), Poisson ration (ν), Young’s modulus (E), and anisotropy (A) of these two precipitates. It is suggested that MgZn2 is stronger than η' for the higher elastic constants but with a better isotropy. Finally, the electronic density of states of η' and MgZn2, together with their influences to the mechanical performance of Al–Zn–Mg alloys were furtherly discussed.

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Funding

The work is financially supported by the National Natural Science Foundation of China (nos. U1637601, U1837207). Special thanks for the helpful discussions with Dolya Shieh and senior scientist Alf Zhu from University of Virginia!

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Authors and Affiliations

  1. Institute of Advanced Structure Technology, Beijing Institute of Technology, 100081, Beijing, China

    Yunlong Ma

  2. Beijing Institute of Astronautical Systems Engineering, 100076, Beijing, China

    Yunlong Ma

  3. China Academy of Launch Vehicle Technology, 100076, Beijing, China

    Ben Lin

  4. Central South University, 410000, Changsha, China

    Zhengbing Xiao & Yuanchun Huang

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  1. Yunlong Ma
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Correspondence to Yunlong Ma.

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Yunlong Ma, Ben Lin, Xiao, Z. et al. First-Principles Study of Mechanical and Electronic Properties of η and η' Phases Present in 7xxx Alloys. Phys. Metals Metallogr. 122, 1257–1263 (2021). https://doi.org/10.1134/S0031918X20140112

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