Abstract: Achieving a balance between strength and ductility in aluminum alloys remains a significant challenge. The design of heterogeneous structures is considered a promising strategy to address this issue. This study proposes a novel thermomechanical processing route to develop Al-4.8Cu-0.65Mn-0.45Mg-0.43Ag alloys with heterogeneous structures. The multi-step processing, which includes hot rolling, cold rolling, annealing, solution, and aging treatments, results in a bimodal grain structure (7.9 µm fine grains and 35.6 µm coarse grains) with multiscale precipitates (127.1 nm T_Mn-Al₂₀Cu₂Mn₃ phase and 89.7 nm Ω-Al₂Cu phase). The resulting alloy demonstrates exceptional mechanical properties, with an ultimate tensile strength of 508.1 MPa, a yield strength of 443.3 MPa, and an elongation of 14.2 %. Microstructural analysis reveals that the hot rolling temperature affects grain size distribution and precipitation behavior. The strength is enhanced by a trade-off in hierarchical features, particularly through a high density of nano-sized phases, which compensate for strength loss caused by grain coarsening. Ductility is enhanced by fine grains surrounding the coarse grains, which coordinate local strain incompatibility at the hetero-interfaces through local reorientations and dislocation slips. This study provides a feasible approach for the controllable design of Al-Cu-Mn-Mg-Ag alloys with heterogeneous structures that exhibit superior strength-ductility synergy.

Key words: Aluminum alloy, Heterogeneous structures, Mechanical properties, HDI strengthening, Ductility