Modulation of precipitation behavior by dislocations and alloying for superior strength-ductility balance in Al-Cu-Li alloys

Conventional T8 heat treatment makes it difficult to achieve the strength and ductility trade-off of Al-Cu-Li alloys, and a feasible strategy to overcome this challenge in this work. Analyzing the microstructures and properties of different aging treatments shows that the transition of sliding dislocation from shear to difficult shear precipitates with increasing T₁ phase size is a major factor in reducing ductility. Effective control of the size of the T₁ phase was achieved by utilizing high dislocation density-assisted heterogeneous nucleation and simultaneous assisted diffusion means combined with precipitation competition between the S' and T₁ phases. Dislocation and alloying to tightly control precipitation after aging, the yield strength (650 MPa) is significantly higher than that of T6 and T85 heat-treated alloys (150 MPa and 30 MPa), and most notably, the elongation reaches 13%. As a consequence, this study is of great significance for the development of high-performance Al-Cu-Li alloys for aerospace applications.