Abstract
The effect of the Mg/Si ratio of Al-2.5Li-1Cu-0.8Mg-0.8Si, Al-2.5Li-1Cu-1.6Mg-0.8Si, and Al-2.5Li-1Cu-2.4Mg-0.8Si alloys on the microstructure evolution and mechanical properties was investigated. The results show that the primary phases and their morphologies in the as-cast alloys are found to vary with the Mg/Si ratio. The improvement of Mg/Si ratio of as-cast alloys promotes the formation of Mg2Si primary phase at the expense of the AlLiSi primary phase. Moreover, a tiny amount of TB-Al7.5Cu4Li phase transforms into S-Al2CuMg phase with the increase of Mg content. In addition, the increase of Mg/Si ratio also causes the Cu-rich intergranular phase distributed along crystal boundary to Si-rich intergranular phase. After ageing treatment, the precipitation sequence as a function of Mg/Si ratio is as follows: δ/δ′+AlLiSi (Mg/Si is ∼1) → δ/δ′+β′-Mg2Si+AlLiSi (Mg/Si is ∼2) → δ/δ′+β′-Mg2Si (Mg/Si is ∼3). A good combination of strength and ductility can be obtained in Al-2.5Li-1Cu-2.4Mg-0.8Si alloy after solution and ageing. The rod-like β′-Mg2Si precipitate has a positive influence on the comprehensive mechanical properties of the alloy.
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This research was financially supported by the National Natural Science Foundation of China (51774105) and Touyan Innovation Team Program (XNAUEA5640208420).
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Zun-jie Wei Ph. D., Professor, Secretary General of Heilongjiang Province Foundry Association. His research interests mainly focus on the solidification theory of nonferrous alloys (Al-base, Mg-base and TiAl alloys) under high pressure, and structural superalloys (Ti-base and Ni-base alloys) advanced casting processes.
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Zhang, Xj., Wang, Hw., Ye, Fb. et al. Regulative effect of Mg/Si ratio on microstructure evolution and mechanical properties of cast Al-Li-Mg-Si alloys. China Foundry 19, 81–88 (2022). https://doi.org/10.1007/s41230-022-1105-3
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DOI: https://doi.org/10.1007/s41230-022-1105-3