EFFECT OF HEAVILY DRAWING ON THE MICROSTRUCTURE AND PROPERTIES OF Cu-Cr ALLOYS

Cu-Cr alloy is a kind of promising materials used as conductor due to its good strength and high conductivity. Heavy cold deformation could increase the strength effectively. Most of Cu and Cr phase are elongated into filaments during cold drawing. There exits plenty of Cu/Cr interface and the structure of Cu/Cr interface is thought to play an essential role in the properties of the Cu-Cr alloy. In this work, Cu-Cr wires were prepared by cold drawing method. The evolution of the microstructure and the structural change of phase interface during cold drawing have been investigated and the relationship between properties and microstructure also established. The microstructure consists of Cu matrix and Cr particles before cold drawing. As the drawing strain increases, both of Cu and Cr phases evolve into filamentary structure. Some residual Cr particles are still found in the alloy even at high drawing ratio. There is a relationship of (111)(Cu)//(110)(Cr) between Cu fibers and Cr fibers at high strain levels. The Cu/Cr interface is non-coherent before cold drawing and gradually evolves into the coherent interface at high drawing strains. The inter-solution ability of Cu and Cr elements across the Cu/Cr interface is enhanced with the increase in the drawing strain. The coherent Cu/Cr interface and the increasing of interface density should be responsible for the strength rising to an almost constant value and the increase in electrical resistivity of Cu-Cr alloys at high strain levels.