Cu-25Ag alloys

Our investigations with continuously cast Cu-Ag alloys showed that maximum strength at minimum drawing strain demands (i) a sufficient volume fraction of eutectic in order to suppress discontinuous precipitation (absence of grain boundaries) and (ii) a sufficiently rapid cooling after solidification in order to prevent pre-precipitation. With a continuously cast starting rod of 12 mm diameter a maximum tensile strength of 1.3 GPa was obtained after a drawing strain of only eta = 4.3. The diagram shows the ultimate tensile strength as a function of the conductivity of drawn Cu-25 wt.% Ag alloys (conditions: as-cast, solution treatment, aging and intermediate heat treatment) with initial billet diameters of 12 mm and 40 mm. The inverse dependence of electrical conductivity and tensile strength is confirmed. A strength level of 1.2 GPa is connected with a conductivity of 70% IACS. In addition, the diagram shows the increase of the conductivity by pre-precipitation and aging as a consequence of the depletion of the Cu solid solution.