Abstract: The 2024 Al-Cu-Mg alloys are critical metallic materials in high-performance aerospace applications. During homogenization, the dissolution/decomposition of intermetallic phases and the precipitation of dispersoids dynamically coexist, governed by the homogenization regimes and can significantly influence the subsequent thermal processing. In this work, we investigated the effects of homogenization temperatures on microstructural evolution and mechanical properties of 2024 alloy through advanced characterization, kinetic analysis, and tensile tests. Results indicate that homogenization at 495 °C for 12 h can dissolve most intermetallic compounds and eliminate micro-segregation, leaving only the AlCuFeMn phase and a small fraction of the S phase distributed along grain boundaries. This process could be well described by an exponential constitutive equation. In this case, the yield strength of the homogenized sample is 288 MPa and the ultimate strength reaches 365 MPa. Based on systematic transmission electron microscope results, the AlCuFeMn phase in the as-cast state was confirmed to be the tetragonal Al₇Cu₂(Fe, Mn), and homogenization heat treatment above the critical temperature of 470 °C could induce the decomposition into tetragonal Al₇Cu₂Fe and cubic Al₂₀Cu₂Mn₃ phases with the OR of [011]_Al20Cu2Mn3//[021]_Al7Cu2Fe, (11)_Al20Cu2Mn3//(100)_Al7Cu2Fe. In addition, atom probe tomography results show the compositional inhomogeneity within decomposed phases, suggesting that adequate solute diffusion is accomplished later than crystallographic structure change. This study reveals in-depth information on microstructural evolution during homogenization and could provide critical reference information for the optimization of homogenization regimes for 2024 alloys.

Key words: 2024 alloy, Homogenization, Intermetallic particles, Phase transition, Mechanical properties