Effect of aging time on the microstructure evolution and mechanical property in an Al-Cu-Li alloy sheet

Abstract

Microstructure plays a crucial role on mechanical properties of materials. The as-prepared Al-Cu-Li alloy exhibits excellent thermal stability during longer aging treatment at 160 °C. Transmission electron microscopy, high angle annular dark field scanning transmission electron microscopy and first-principle energy calculations were used to evaluate the evolution of different phases in the alloy. The results show that the microstructure evolution goes as follows: SSS→δ′ θ′ T1→θ′ T1, cubic Al5Cu6Li2 phase. The cubic Al5Cu6Li2 phase was not precipitated from the matrix until 104 h aging, and the number density increased with prolonging of aging time. Its formation compensates the strength loss caused by the decreased number density and coarsening of θ′(Al2Cu) and T1(Al2CuLi) during longer aging treatment.