Anisotropy in creep ageing behavior of textured Al-Cu alloy under different stress states

Deformation and properties are both important factors in understanding creep ageing behavior, especially for textured alloys subjected to a complex stress-state. Creep deformation and tensile properties of a textured Al-Cu alloy after tension and compression creep tests were evaluated at different orientations with respect to the rolling directions. From these observations, the in-planar anisotropy (IPA) of creep deformation and yield strength were calculated and correlated with textures and microstructures of the alloy. It has been found that the creep strain after tension and compression creep tests are largest when the applied stress is along the rolling direction (RD) and smallest when the applied stress is along the transverse direction (TD). The as-received alloy has obvious in-planar anisotropy of yield strength, but this anisotropy basically disappeared after ageing. The different stress states cause different creep mechanisms and also affect the evolution of dislocation density. It was found that the dislocation density is highest when the tensile stress is applied along the TD, while the dislocation density in different stress orientations is basically the same under compressive stress. This should be the main reason that the IPA of creep strain after compression creep test (25.4%) is greater than that after tension creep test (15.0%).