Nucleation and growth of γ-Fe precipitate in Cu-2%Fe alloy aged under high magnetic field

• HMF promoted semi-coherency from coherency in γ-Fe.
• HMF increased the electrical conductivity at 700 °C.
• HMF increased the diffusion coefficient of Fe in Cu.

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 h, 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.

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