Aging Temperature-Dependent Precipitation Characteristic and Strengthening Mechanisms in a Zn-Modified Al-Cu-Li Alloy with Multi-Alloying (Mg, Ag, Zr)

Promising Al-Cu-Li alloys with 1 wt.% Zn content and multi-alloying elements (Mg, Ag, Zr) represent an optimal compositional design. However, studies on the influence of aging temperature on their precipitation behavior and strengthening mechanisms remain limited. This study systematically investigates the aging temperature-dependent precipitation characteristics and strengthening mechanisms in a novel Zn-modified Al-Cu-Li alloy. Aging kinetics accelerate with temperature, and peak tensile properties (yield strength: 607 MPa, ultimate tensile strength: 636 MPa) are achieved at 180 °C/12 h, representing a 29% yield strength improvement over the Zn‑free counterpart. Crucially, Zn addition triggers exclusive nucleation of blocky T B (Al₇Cu₄Li) and an unidentified X phase at ≥180°C, both enriched in Cu, Zn, Mg and Ag. Moreover, Zn maximizes the T₁ (Al₂CuLi) volume fraction (2.08%) and increases its average diameter (137 nm vs. 93 nm in Zn-free alloy). The superior strengthening is attributed to synergistic effects from T₁, T B , X, and θ′ (Al₂Cu) phases. These findings provide critical insights for optimizing aging parameters and compositional design of high-performance Al-Cu-Li alloys.