AL-Zn-Mg-Cu (7xxx series) alloy as an ultra high strength aluminum alloy is widely used in the aerospace industry due to its excellent mechanical properties. In order to further improve the comprehensive mechanical properties of alloys, different solid solution aging processes are often adopted. Solid solution treatment can affect the grain size and morphology of the alloy and the solid solution degree of strengthened elements. The purpose of aging is to precipitate a large amount of fine and dispersed second phase from the supersaturated solid solution so as to strengthen the alloy matrix. The most important factors affecting solid solution and aging precipitation are temperature and time. Because the single-stage solid solution process cannot make the alloying elements fully soluble in the matrix, and the transition liquid phase is easily generated in the alloy, thus weakening the grain boundary [6]. Therefore, the solid solution degree of the alloy can be effectively improved by adopting multi-stage solid solution and gradually increasing the solid solution temperature to above the melting point of polyphase eutectic, which has a positive effect on the subsequent aging precipitation degree.

Recently, the research team of Professor Xiaojing Xu innovated the design concept of ultra high strength aluminum alloy and found a AL-Zn-Mg-Cu (7xxx series) alloy with excellent processing performance, high strength, and toughness.The aluminum alloy extrusion materials were treated by multi-stage solution aging, and the microstructure and mechanical properties were characterized and tested. the aluminum alloy has excellent comprehensive properties, with a strength of 828.0 MPa and elongation of 8.1%.

The paper links: https://www.sciencedirect.com/science/article/pii/S0167577X19310687