Study on Microstructure and Properties of High-strength-toughness Al-9Si-xCu-yMg Alloy

Abstract The existing Al-Si-Cu-Mg alloys cannot meet the needs of new energy automobile parts with low cost and high performance due to difficulty in reconciling high strength and low plasticity. In this study, a systematic research method combining thermodynamic calculation and experiment was adopted, and alloy composition, microstructure and mechanical properties of the Al-9Si-2.5Cu-0.5Mg alloy were investigated by adjusting the content of Cu, Mg and the heat treatment process. The results show that, as Cu and Mg content increase, the strength of the alloy increases first and then decreases, but the elongation decreases significantly. When the Cu content is 2.5% and the Mg content is 0.5%, there exists an optimal combination between the strength and elongation, and the tensile strength of 387MPa, and elongation of 4.15% are achieved. The microstructure and mechanical properties of Al-9Si-2.5Cu-0.5Mg alloy can be improved by adding modifier Al-Sr, grain refiner Al-5Ti-B and appropriate heat treatment process, and the improvement of the comprehensive mechanical properties mainly benefits from the fine grain strengthening and the precipitation strengthening. The research work is expected to provide theoretical basis and practical guidance for the optimal design of high-strength-toughness Al-Si-Cu-Mg alloy.