Achieving dual improvement of microstructure and mechanical properties of 7449 alloy through homogenization annealing

As a representative heat-treatable aluminum alloy, the 7xxx series exhibits outstanding overall properties when subjected to heat treatment, making it a key structural material in aerospace applications. However, the dissolution and precipitation behavior of new generation 7449 alloy ingots during homogenization annealing remains underexplored. To facilitate its broader application, systematic research is necessary. This study investigates the homogenization annealing process of 7449 alloy ingots through an orthogonal experiment conducted within the 420–480 ℃ temperature range. It explores the influence of various homogenization parameters on the network eutectic phase and how the evolution of secondary phase precipitation affects the alloy's mechanical properties. SEM analysis shows that as the heating temperature increases, the dissolution rate of eutectic phases accelerates, enhancing the alloy's degree of homogenization. This improvement results in increased yield strength and hardness. After homogenization at 460 ℃ for 24 h, the content of secondary phase particles is significantly reduced, and their size is refined. This leads to a remarkable improvement in the alloy's room-temperature mechanical properties, with tensile strength, elongation, and hardness increasing by 216%, 176%, and 235%, respectively. The study reveals that during the homogenization annealing of 7449 alloy, the precipitation of a substantial amount of Al₃Zr dispersion phase. This is the primary mechanism responsible for the alloy's enhanced strength and toughness. This study effectively addresses the homogenization process design and second-phase regulation of 7449 alloy ingots, laying a solid foundation for the optimized application of this critical aerospace structural material.