Effects Of Cold Drawing And Heat Treatments On Microstructure And Properties Of Cu-Ag-Fe Microcomposites

Cu-Ag-Fe filamentary microcomposites were prepared by heavy cold drawing and different heat treatments. The characteristics and evolution of the microstructure during cold drawing were investigated. The effects of cold drawing, content of Fe and heat treatments on the microstructure and properties are discussed.The microstructure of as-cast Cu-Ag-Fe alloy mainly contains Cu matrix, Cu/Ag eutectics and primary Fe dendrites. After homogenizing, the fraction of Cu/Ag eutectics decreased and the primary Fe dendrites were refined. The solute segregation was removed and more secondary Ag and Fe particles could be found in Cu matrix.During cold drawing, the alloy developed a typical filamentary and ribbon microstructure. When strian is small, the filament has a cured morphology and not straight. As strian increased, the filaments and the interval of the internal interface between them decreased. Since there are three different interfaces exist in the alloys, the homogeneous deformation is difficult and the difference between different phase filaments is significant.The strength and hardness increase and the conductivity decreases with the increase in draw ratio. The strengthening mechanism changes from dislocation model to interface obstacle model. The decrease of conductivity is mainly due to the increased interface scattering.The strength increases and the conductivity decreases obviously with the increase of the content of Fe. The difference of strength becomes larger with the increase in the deformation. The decrease trend of electrical conductivity is_similar.Heat treatment before drawing strain facilitates the deformation of Fe dendrites and promotes the precipitation of Ag and Fe, which improves the strength and conductivity level during deformation. However the decrease of conductivity has a high ratio than the alloys without heat treatments before drawing strain.For the alloys annealed at 200℃, the tensile strength and conductivity show slight change. When the annealed temperature is higher than 200℃. the tensile strength decreases and the conductivity increases significantly. Annealed at higher temperature, the change trends of strength and conductivity slow down again.