High-strength and high-toughness cast Al-Mg-Zn alloy and preparation method thereof

The invention relates to the technical field of metal material processing, and discloses a high-strength and high-toughness cast Al-Mg-Zn alloy and a preparation method thereof. The aluminum alloy comprises, by mass, 3%-6% of magnesium (Mg), 6%-9% of zinc (Zn), 0.6%-1.2% of manganese (Mn), not larger than 0.1% of inevitable impurity element iron (Fe), not larger than 0.25% of other inevitable impurity elements in total, and the balance pure aluminum. The morphology of impurity iron is regulated and controlled by adding the Mn element, the adverse effect of the impurity iron on plasticity is weakened, and the impurity iron is dissolved in an Al matrix to improve the mechanical property of the alloy. And extrusion casting waste heat is used for quenching treatment, so that the strength and ductility of the alloy are obviously improved, and the requirements of high strength and high toughness of the aluminum alloy for the automobile structural part are met. 本发明涉及金属材料加工技术领域，公开一种高强高韧的铸造Al-Mg-Zn合金及其制备方法。所述铝合金包括下述质量