Deformation-Processed Cu-Fe In-situ Composites

Deformation-processed Cu-Fe in-situ composite was manufactured by inductive melting, casting, swaging, rolling and wire drawing. Microstructural observations were carried by optical microscope, SEM, TEM and XRD. The Cu-Fe alloy consisted of Cu phase and a-Fe phase. The Fe dendrites were randomly distributed in the as-cast samples and were aligned parallel to the wire axis at the begin of deformation. During deformation the Fe phase elongated into ribbons and the microstructure refined. After small amounts of deformation the Fe morphology appeared quiet inhomogeneous, and the deformation began at the end of Fe dendrites. Atfer higher amounts of deformation the Fe ribbons had more uniform shape. The intermediate heat treatment can accelerate this process. The relationship between the thickness of Cu phase, Fe ribbons and the strain can be described by expression t=ae^-cη, and it was influenced by Fe content and intermediate heat treatment.The strength of deformation-processed Cu-Fe in-situ composite was measured by MTS. The results were shown to be anomalously higher than those predicted by rule of mixture equations. The strength increased with increasing of the deformation. However, the strength follows a Hall-Petch type relationship with the Fe ribbon spacings. The strengthening mechanism was discussed. The analysis indicated that the substructural especially phase boundary strengthening plays the crucial role. The experimental data are in good accord with the predictions of the geometrically-necessary dislocation model and interface as dislocation source model.The electrical resistivity of the composites wires was experimentally investigated by four-point measure. The electrical resistivity of these composites increased with the deformation, Fe content in alloy and Fe solubility in Cu matrix. The observed increase in resistivity with increasing wire strain is interpreted in terms of inelastic electron scattering at internal phase boundaries. Fe dissolved in the Cu matrix will make an great impurity scattering contribution to the resistivity. A series of intermediate heat treatment was done at various stages of the wire-drawn to promote precipitation of the Fe from the Cu matrix, and improved the electrical conductivity. The relationship of electrical resistivity and microstructural scales was discussed. The experimental data are in good accord with the predictions of an analytical size-effect model.The shape changes of Fe ribbons in deformation-processed Cu-Fe in-situ composite during annealing were observed by optical microscopy and SEM. The results found that the instability of Fe ribbons has three processes: direct cylinderization plus Rayleigh perturbation, edge spheroidization, longitudinal splitting plus cylinderization plus Rayleigh perturbation. The breakup kinetics of Fe filaments were monitored by quantitative metallography. Experimental results were compared with existing models and the appropriate physical model for breakup of filaments was provided.A curve of optimum tensile strength against electrical conductivity was determined. It is suggested that further improvements may be possible in Cu-Fe alloys by improved thermal mechanism processing.