Effects of texture and precipitates characteristics on anisotropic hardness evolution during artificial aging for an Al–Cu–Li alloy

Abstract

Anisotropy of mechanical properties has limited the further application of Al–Cu–Li alloys. Previous research efforts were mostly focused on the anisotropic tensile properties. In the present study, significant hardness anisotropy evolution, measured during artificial aging, was also established when loading in different directions. It was found that different amounts of inclined/face-on would be encountered when loading along different directions, resulting from the fiber texture and inhomogeneous distribution of T1 (Al2CuLi) variants along different directions for the samples without pre-stretching. The resistance to hardness loading is different between the face-on/inclined T1 and edge-on T1 due to its high aspect ratio, so the measured anisotropic hardness is obtained. Moreover, the characteristics of precipitates also play an important role in the anisotropic hardness evolution, the strong anisotropy of hardness only appears in the alloys that contained large diameters and a low density of T1 phase or θ' (Al2Cu) phase. After applying pre-stretching, the predominant T1 phase precipitates with small diameters and a high density, which helps to facilitate the isotropic hardness evolution during artificial aging. These findings provide a necessary supplement for the hardness evaluation where a high aspect ratio of precipitate is involved.

Keywords

• Al–Cu–Li alloy
• Aging hardening
• Anisotropy
• Texture
• Precipitate