Precipitation strengthening of stress-aged Al-xCu alloys

Effects of stress aging on yield strength and yield anisotropy of single cr ystal and cube-textured polycrystalline Al-xCu alloys were investigated. Th e resulting microstructures were correlated with the yield stress and analy zed with respect to continuum mechanic models and computer simulations. The yield stresses of the stress-aged specimens, were found to be lower than t hose 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 theta{100}-plates as well as to their "detrimentally" different volume fraction and/or morph ology in the stress-aged specimen subjected to the same thermal treatment a s the stress-free-aged specimen. When compared with the continuum models, b oth of which account for only effects of the orientation and volume fractio n of the theta(100)-plates, the computer simulation of interaction between slip dislocation and unshearable plates, which additionally incorporates th e effect of plate morphology, yields the closest results to those obtained experimentally. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Scien ce Ltd. All rights reserved.