Characterization of aging properties and precipitation of copper base alloys

This article describes recent progresses in the microstructural characterization of precipitates in several copper base alloys and the mechanical and electrical properties of the alloys. To improve the strength and electrical conductivity of Cu-Ti and Cu-Ni-Si alloys, the effects of composition and cold-work treatment prior to aging treatment on these properties are examined. The properties of the alloys are found to be improved by precipitation during aging. The small-angle X-ray scattering method and X-ray absorption fine structure analysis are used for characterizing the precipitates formed. Our results show that there is an optimum size of precipitates for obtaining high strength, although the electrical conductivity monotonically increases with aging time. We also show that cold rolling after solution treatment is effective in increasing the strength and electrical conductivity of the alloys. We discuss the precipitation mechanism in the cold-rolled alloys on the basis of the experimental results.