Residual resistivity and aging-clustering effects of Cu-rich Cu-Ni alloys

The residual resistivities of copper-nickel alloys with nickel concentrations ranging from 20 ppm to 44 at.% and the observation of Ni-cluster growth at room temperature on one sample are reported. From samples arc-melted over a Cu hearth, wires 1 mm in diameter were drawn, annealed at 800 °C for 3 days, and quenched in ice water. Pieces of wire adjacent to the samples were used for chemical analysis on the 3-44-at.% samples and parts of the samples were used for spectrophotometric analysis on the dilute alloys. Results show that the resistivity at 4.2 °K over the concentration range studied is given by $\rho -{\rho }_{\mathrm{Cu}}\left(4.2\mathrm{} °\mathrm{K}\right)=1.112x$ (μΩ cm/at.% Ni), where $x$ is the nickel concentration in at.%. By chance the electrical resistivity from 1.3 to 300 °K of samples of ${\mathrm{Cu}}_{1-x}{\mathrm{Ni}}_x$ ($x=0.32\mathrm{} \mathrm{and} 0.44$) were remeasured after they had been on the shelf at room temperature for 3 years. The new results showed that the electrical resistivity of the $x=0.44\mathrm{}$ sample had changed quite markedly. The sample was then reannealed at 800 °C and quenched in ice water, and the resistivity was measured for the third time. The sample again took on nearly the same character it had originally displayed. The nature of the change of resistivity with shelf time suggests that Ni-cluster growth at room temperature occurred.