High strength and high conductivity nanoparticle-precipitated copper ally : optimizaiton of thermomechanical processing

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Crystallography and morphology of precipitate particles in Cu-Fe-Co, Cu-Co-Cr and Cu-Ni-Si alloys were investigated. From experiments using Cu-Fe-Co alloys, it has been found that fcc Fe-Co particles transform into bcc particles by applying magnetic field. Transformability of the particles strongly depends on the particle size, cooling rate and the composition of the particles. It has been found that the magnetic field is useful to control microstructures without any deformation of a specimen.Through extensive investigation using Cu-Ni-Si alloys, it has been found that the crystallographic orientation relationship between Ni_2Si precipitate particles and a Cu matrix, (110)_<Cu>//(001)_<Ni2Si>, [001]_<Cu>//[010] _<Ni2Si>, is satisfied. The Ni_2Si particles tend to grow along the invariant-line direction. The strength is strongly affected by not only the size but also the shape of particles. The elongated shape of the particles results in retarding the peak aging time. We concluded that we are able to obtain the optimum aging condition for the maximum strength with precise consideration of the shape of particles.