Precipitation strengthening of stress-aged Al–xCu alloys

Effects of stress aging on yield strength and yield anisotropy of single crystal and cube-textured polycrystalline Al–xCu alloys were investigated. The resulting microstructures were correlated with the yield stress and analyzed with respect to continuum mechanic models and computer simulations. The yield stresses of the stress-aged specimens, were found to be lower than those of the stress-free-aged specimens whether the test direction was along or perpendicular to the aging-stress direction. This was attributed to the effect of stress-induced preferential orientation of the θ′{100}-plates as well as to their “detrimentally” different volume fraction and/or morphology in the stress-aged specimen subjected to the same thermal treatment as the stress-free-aged specimen. When compared with the continuum models, both of which account for only effects of the orientation and volume fraction of the θ′{100}-plates, the computer simulation of interaction between slip dislocation and unshearable plates, which additionally incorporates the effect of plate morphology, yields the closest results to those obtained experimentally.