| CHEN Jing-chang,LIU Jian-guo,LU Shao-min,ZHONG Li-hui,CHEN Li-ping,WANG Yuan.First-principles Calculations of Stability, Electronic Structure and Mechanical Properties of Y-doped MgZn2[J],52(8):444-450 |
| First-principles Calculations of Stability, Electronic Structure and Mechanical Properties of Y-doped MgZn2 |
| Received:July 20, 2022 Revised:February 16, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.08.040 |
| KeyWord:MgZn2 Y doping electronic structure mechanical properties first principles calculation |
| Author | Institution |
| CHEN Jing-chang |
Southwest Forestry University, Kunming , China |
| LIU Jian-guo |
YYCIN No.7 Construction Co., Ltd., Kunming , China |
| LU Shao-min |
Southwest Forestry University, Kunming , China |
| ZHONG Li-hui |
Southwest Forestry University, Kunming , China |
| CHEN Li-ping |
Southwest Forestry University, Kunming , China |
| WANG Yuan |
Southwest Forestry University, Kunming , China |
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| Abstract: |
| Micro-alloying of rare earth element Y is an important way to strengthen the fracture toughness of 7xxx series aluminum alloys, but it is hard to determine the effect of Y doping on the precipitated phase and toughness mechanism of 7xxx series aluminum alloys in experiments because the doping amount of Y is very small, which limits the further development of 7xxx series aluminum alloys. Therefore, the influence mechanism of Y doping on the important precipitation phase MgZn2 in 7xxx series aluminum alloys was analyzed by the first principles calculation method in this paper, in order to provide a theoretical basis for study of the strengthening and toughening mechanism of 7xxx series aluminum alloys by micro-alloying elements. A crystal model with the atomic ratio of Mg/Zn=1∶2, which was suitable for first-principles calculation, was built in this paper, then Mg or Zn atoms were replaced with Y atoms by orderly substitution doping and the influence mechanism of Y doping on the energy stability, electronic structure and mechanical properties of MgZn2 was analyzed by energy calculations, electronic calculations and elastic constant calculations. The results showed that after Y doping, the formation heat of Mg3Zn8Y, Mg4Zn7Y-1 and Mg4Zn7Y-2 was −19.998, −7.14 and −3.916 kJ/mol respectively, so the three solid solutions could spontaneously form and exist stably. It could be found that the structural stability of MgZn2 could be enhanced by Y doping, and the formed solid solution Mg3Zn8Y with Y substituting for Mg had the most stable structure and the formed solid solution Mg4Zn7Y-2 with Y substituting for had the worst stability, since the binding energy of MgZn2, Mg3Zn8Y, Mg4Zn7Y-1 and Mg4Zn7Y-2 were −132.664, −163.584, −153.648 and −150.424 kJ/mol, respectively, obtained from the computation of binding energy. The solid solution Mg4Zn7Y-2 hardly formed with Y doping due to their poor formation ability and structural stability, so the electronic structure and mechanical property analysis didn’t be considered in this paper. Secondly, it was discovered that Mg-Zn atom formed an ionic bond and the main covalent bond in MgZn2 came from Zn-Zn atom without Y doping from the analysis of electronic structure. When Y atoms were doped, the main covalent bond in the system came from the bonding between Y, Zn or Mg atoms, the covalent bond of Zn-Zn atoms was converted into a stronger ionic bond, and the ionic bond between Mg-Zn atoms was likewise considerably strengthened. The doped Y atoms formed a strong covalent bond with other atoms, which promoted the stability of the system. It could be concluded that the metallic character of the system increased and the Mg4Zn7Y possessed the strongest metallic character from the analysis of the gross density of states. Finally, the mechanical property calculation showed that the hardness of MgZn2 decreased and the toughness increased after Y doping, i.e., Y doping enhanced the toughness of the important dispersed precipitation phase MgZn2 in 7xxx series aluminum alloys, and consequently increased the fracture toughness and anti-fatigue ability of 7xxx series aluminum alloys. Based on the above calculation and analysis, the doped Y can improve the stability, bond strength and fracture toughness of MgZn2 phase. In addition, relevant calculation and analysis can provide a guidance for experimental analysis on enhancing the fracture toughness of 7xxx series aluminum alloys by a little Y doping. |
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