DEFORMATION-PROCESSED COPPER-CHROMIUM ALLOYS - ROLE OF AGE-HARDENING

A processing technique was developed previously to optimize strength and electrical conductivity in deformation-processed copper-chromium wires. It consists of deformation treatments alternated with a solution plus quench treatment and then with an aging treatment. In the present study, samples were examined by transmission electron microscopy at each stage of the optimized process to follow the evolution of microstructure. It was shown that this type of processing develops maximum reduction in size of the chromium dendrite phase without breakage and that the deformation produces a strong precipitation of the chromium from solid solution. The aging treatment does not produce an age-hardening effect. Rather, it produces precipitation of chromium on the existing chromium filaments and relieves the strain in them so that additional reduction by deformation is possible. Additional experiments on copper-niobium alloys, which are not expected to show age hardening, also support these conclusions.