Stress aging of Al–xCu alloys: experiments Original Research Article

Exposure of age-hardenable aluminum alloys to an elastic loading, either for “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 precipitates in the alloys. Preferentially oriented θ″/θ′-precipitate structures were quantitatively examined in single-crystal Al–2.5Cu, Al–4Cu and cube-textured Al–5Cu alloys aged to peak strength under compressive stresses. The dependence of the stress orienting of the θ″/θ′-precipitates on the applied stress, aging temperature and the copper content were determined. The effect is discussed and explained within the frame of classical nucleation and growth theories that incorporate the interaction energy between the external stress and the strain fields due to the lattice misfits between the θ″/θ′-precipitates and the Al matrix.