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Cu-2wt%Fe alloy, an inexpensive candidate for a high strength conductor, depends for its conductivity on the precipitation of Fe. We applied an external 12 T high magnetic field (HMF) during ageing treatment of this alloy in order to study the resulting γ-Fe precipitation on the electrical conductivity. When the alloy was aged at 450 °C for up to 16 hrs, coherent γ-Fe precipitates formed within the Cu matrix. Between the γ-Fe precipitates and the Cu matrix, the lattice misfit was 1.4%±0.7% and the angle between closed packed planes was about 0.3. These γ-Fe precipitates became semi-coherent with the surrounding Cu matrix in samples aged at 700 °C for over 0.5 h. HMF made insignificant contributions to both the morphology and the volume fraction of γ-Fe at 450 °C. At 700 °C, however, HMF promoted a transformation from coherent to semi-coherent γ-Fe precipitates. Applying HMF during ageing at 700 °C increased electrical conductivity. HMF had little influence on the nucleation of γ-Fe precipitation. We applied the Lifshitz-Slyozov-Wagner (LSW) formula to the coarsening data of the precipitates and determined that HMF increased the diffusion coefficient of Fe in Cu and promoted the growth of γ-Fe precipitation out of the Cu matrix.

a b s t r a c tUnderstanding the precipitate kinetics of Ag in proeutectic Cu is valuable to optimize the precipitation and morphology of Ag for high strength high conductivity hypoeutectic Cu-Ag alloys. The precipitation behaviors of as-solution treated Cu28 wt.%Ag alloys were analyzed by differential scanning calorimetric (DSC). The results indicated that the activation energies of Ag-rich phase formation and dissolution were 55.3 ± 22.4 kJ/mol and 129.1 ± 20.7 kJ/mol, respectively. The as-solution alloy was further aged at different temperatures for 2 h. Their microhardness and electrical resistivity were measured. The results demonstrated that at the ageing temperature of 405°C, less scattering effects reflected more Ag precipitations from Cu matrix than the rest of temperatures. At 475°C, however, Ag precipitates produced more strengthening effects. Above results were related to the competition between precipitation and dissolution of Ag in proeutectic Cu. This interpretation is supported by TEM observations on Ag precipitation.

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