Optimization design of 7A52/7A62/7A52 aluminum alloy laminated composite sheet by modifying layer thickness ratio and annealing treatment

High-strength 7xxx Al alloy laminated composites are promising for armor protection applications. However, achieving a superior synergy of strength, ductility, and impact toughness through systematic structural design and post-processing remains challenging. Hence, this work designed and developed a series of symmetrical 7A52/7A62/7A52 laminated composite sheets with different layer thickness ratios through the roll bonding method. Firstly, the optimal layer thickness ratio was determined through quasi-static tensile tests, three-point bending tests, and high-speed impact compression tests. Afterwards, a Johnson-Cook constitutive model was established to characterize the dynamic mechanical behavior under high strain rate conditions. Finally, the optimally designed composite sheet was selected to further perform different annealing treatments for modifying mechanical properties. The results showed that the multilayer structure can cause multiple crack deflections and crack blunting during propagation, resulting in the superior performance of composite sheets over the components. The composite sheet with a layer thickness ratio of 2:8:2 possesses the best strength-plasticity combination, demonstrating the UTS of 415.7 MPa and EL of 15.2%. Under high strain rate impact, this composite demonstrated excellent energy absorption, reaching 423.7 MJ/m 3 , which is 12.1% and 24.4% higher than those of the 7A52 and 7A62 monolayers, respectively. Besides, the indistinguishable interface indicates that a strong metallurgical bond between the constituent layers can be formed after annealing. Due to the occurrence of recrystallization and precipitation evolution, annealing treatments can lead to an enhanced ductility for the optimally designed sheet despite deteriorated strength.