Effect of heat treatment on the microstructure and mechanical properties of rapidly solidified 7091 P/M aluminium alloy

The application of rapid solidification processing to aluminum alloys has led primarily to two important developments -- namely, microstructural refinement and extension of solid solubility. Cobalt, normally an insoluble element in aluminum, has thus been incorporated into the chemistry of the high-strength 7XXX alloys, giving rise to the first generation of Alcoa-make corrosion-resistant, rapidly solidified P/M 7090 and 7091 aluminum alloys. Specimens of the high-strength P/M 7091 aluminum alloy were subjected to different aging treatments. The effect of the microstructural changes, mainly the precipitation of particles at grain boundaries and within the grains, as well as the effect of the initial microstructure on the mechanical properties of the alloy were investigated by scanning electron microscopy and are discussed in this paper.