Effects of solution and aging treatments on the microstructure and mechanical properties of cold rolled 2024 Al alloy sheet

Abstract The effects of solution and aging on the microstructure evolution, mechanical properties and conductivity of cold rolled 2024 Al sheet were clarified. The results showed that the 2024 Al sheet mainly had the second phases of Al7Cu2Fe, S (Al2CuMg) and θ (Al2Cu). During the solution stage, S and θ phases gradually dissolved into Al matrix, resulting in a great improvement of mechanical properties and conductivity. The static recrystallization and grain growth also occurred during solution, while the grain growth was inhibited by T (Al20CuMn3) particles. GPB zones and S phases precipitated during artificial aging, which acted as the main strengthening phases. Before peak-aging, the amount of GPB zones and S phases increased, and the strengthening effect was enhanced. The precipitates reduced the number of electron scattering sources in the matrix and thus enhanced the conductivity. The optimal solution condition was determined as 500 °C × 70 min and the optimal aging condition was determined as 180 °C × 16 h, by which the excellent ultimate tensile strength of 527 MPa, yield strength of 411 MPa, elongation of 12.5%, hardness of 148.9 HV and conductivity of 37.4%IACS were achieved.