Precipitates evolution during artificial aging and their influence on mechanical properties of a cast Al–Cu–Li alloy

Abstract

Al–Cu–Li cast alloy components also show a promising application in the aerospace industry due to their relatively good combination of density and performance. According to the conventional processing procedures for cast products, a novel cast Al–Cu–Li alloy was directly solution treated and aged after homogenization, then the aging precipitation behavior and its effect on the mechanical properties of the alloy were investigated in this article. It was found that the naturally aged precipitates are rapidly dissolved during artificial aging at 175 °C, and the cubic phase, θ′ phase, T1 phase, Ω phase, and S phase will precipitate successively. In the early stage of artificial aging, the cubic phase and θ′ phase are formed prior to the T1 phase. With the aging time increasing, numerous T1 phases also precipitate with relatively large diameters, so the hardness of the alloy keeps rising until to the peak value. The naturally aged specimens show good plasticity and relatively low strength. After artificial aging, the tensile strength of the cast alloy can be increased to 423 MPa, but the corresponding elongation has a significant reduction. Moreover, the predominant precipitates—T1 phase and cubic phase show excellent thermal stability during 175 °C aging, they still exist with a large population even aged for 40 days.

Keywords

• Al–Cu–Li alloy
• Artificial aging
• Precipitate evolution
• Mechanical property