The inhibiting effect of dislocation helices on the stress-induced orientation of S' precipitates in Al-Cu-Mg alloy

The phenomenon of restrained stress-induced preferential orientation of S′ precipitates is investigated using a single-crystal of Al-1.23Cu-0.43 Mg alloy. Al-1.23Cu-0.43 Mg single-crystal specimens are subjected to stress aging, and the microstructure is analyzed by transmission electron microscopy (TEM). It is found that the stress-induced preferential orientation of S′ precipitates is restrained owing to the dislocations produced by a higher stress. The effect of dislocations on the oriented precipitates depends on the total length of the intersection lines for precipitate habit planes and dislocation glide planes. This investigation not only provides important insight into solving the anisotropy problem attributed to precipitation strengthening, but also offers a benchmark for choosing the appropriate stress range in manufacturing of Al-Cu-Mg alloys.