Stress aging of Al-xCu alloys: Experiments

Exposure of age-hardenable aluminum alloys to an elastic loading, either fo r "age-forming" and other manufacturing processes or during utilization at relatively high temperature, may lead to microstructural changes such as a stress-orienting effect of plate-like coherent or semi-coherent precipitate s in the alloys. preferentially oriented theta"/theta'-precipitate structur es were quantitatively examined in single-crystal Al-2.5Cu. Al-4Cu and cube -textured Al-5Cu alloys aged to peak strength under compressive stresses. T he dependence of the stress orienting of the theta"/theta'-precipitates on the applied stress, aging temperature and the copper content were determine d. The effect is discussed and explained within the frame of classical nucl eation and growth theories that incorporate the interaction energy between the external stress and the strain fields due to the lattice misfits betwee n the theta"/theta'-precipjtates and the Al matrix. (C) 2001 Acta Materiali a Inc. Published by Elsevier Science Ltd. All rights reserved.