Parameters influencing the electrical conductivity of CuCr alloys

Copper-Chromium alloys are commonly used as contact materials for energy distribution. One of the major requirements is a good electrical conductivity for non-dissipative conduction of the nominal current. Since Cu and Cr are mutually nearly insoluble, CuCr alloys are two-phase composites, usually consisting of chromium particles embedded in a copper matrix. A decrease in electrical conductivity following e.g. a change in process parameters may be caused by (a) the geometry of the Cr phase, (b) phase boundaries between Cr particles and Cu matrix, or (c) diffusion of impurities into the Cu matrix. In the present work the influences of these different factors on the electrical conductivity of powder metallurgically produced CuCr25 material will be investigated. Regarding microstructure, several theoretical (analytical) models are available in literature, which do, however, not explicitly consider measurable features of the microstructure. We tackle this problem by combining quantitative microstructural analyses with an empirical relationship generated from FEM simulations based on simplified microstructures to obtain a prediction of the electrical conductivity of the composite. The electrical conductivities determined show considerable deviation from experiment, which is ascribed to the above mentioned factors (b) and (c) having not been incorporated into the model yet. However, the comparison of longitudinal and transverse conductivity measurements enables the separation and quantification of the effects arising by phase boundaries and impurities.