| METALS AND METAL MATRIX COMPOSITES |
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| Effects of Zn on the Stability of the Aging Precipitates in Al-Mg-Si Alloys by First Principles Calculations |
| YU Rui1,2,3, ZHANG Yong'an1,2,3,*, LI Yanan1,2,3, LI Xiwu1,2,3, LI Zhihui1,3, YAN Lizhen1,2,3, WEN Kai1,2,3, XIONG Baiqing1,3
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1 State Key Laboratory of Non-ferrous Metals and Processes, GRINM Group Co., Ltd., Beijing 100088, China
2 GRIMAT Engineering Institute Co., Ltd., Beijing 101407, China
3 General Research Institute for Nonferrous Metals, Beijing 100088, China |
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Abstract Al-Mg-Si alloys are widely used in automobiles due totheir sufficient strength, high surface quality after welding and excellent corrosion resistance. As a series of heat-treatable alloys, Al-Mg-Si alloys' strength can be improved as much as possible by increasing the aging response rate. At present, Zn is generally added to the alloys to promote the aging precipitation, but the effects of Zn on the stability of the aging precipitates are still unclear. Thus, the lattice constants and formation enthalpies of possible Mg-Si phases (including Mg-Si GP zones, β″ phase) and Mg-Zn phases (including Mg-Zn GP zones, η′ phase) in Al-Mg-Si alloys with Zn added were calculated using first-principles calculation. The results reveal that the formation enthalpies of the four possible structures of Mg-Si GP-zones are in the order of Mg2Si1Al3> Mg2Si3Al6> AlMg4Si6> Mg1Si1, which are all lower than that of Mg-Zn phases, indicating that the Mg1Si1 structure is the most stable one, and it is difficult to form Mg-Zn phases in Al-Mg-Si alloys containing Zn element. Furthermore, the lattice constant, formation enthalpy, and electronic density of states of Zn atoms before and after doping in the Mg1Si1 GP region and the peak-aged precipitated phase β″ phase were calculated. The results showed that the doping of Zn can reduce the formation enthalpies of Mg-Si GP-zones and β″ phase, and increase the width of pseudoband gap. The formation of GP-zones and β″ phase during the aging stage of Al-Mg-Si alloys is promoted due to the improved stability of the structures. As a result, the aging hardening response of the alloys is improved.
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Published: 25 February 2023
Online: 2023-03-02
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| Fund:Key R&D Program of China (2016YFB0300802). |
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2023, Vol. 37 
