Microstructure and property of stress aged Al-Cu single crystal under various applied stresses

The stress aging behavior of Al-Cu alloy under various applied stresses, i.e., elastic stress, yield stress and plastic deformation stress, was investigated using single crystals. The resulting microstructures and the yield strength were examined by transmission electron microscopy (TEM) and compression tests, respectively. The results indicate that an elastic stress of 15 MPa is high enough to influence the precipitation distribution of θ′ during aging at 180 °C. The applied stress loading along direction results in increased number density of θ′ on (001)Al habit planes. This result becomes more significant with increasing applied stress and leads to lower yield strength of Al-Cu single crystals during aging. Moreover, the generation of the preferential orientation of θ′ was discussed by the effect of the dislocation induced by applied stress as well as the role of the misfit between the θ′-precipitate and Al matrix. The results are in agreement with the effect of the latter one.