Plastic Deformation of Cr Phase in Cu-Cr Composite during Cold Rolling

A heavily deformed Cu-Cr in situ composite is quite promising as a material with high strength and high conductivity, while polycrystalline Cr itself is well known to be brittle at room temperature. In order to make clear why the Cr phase in the composite is ductile, texture formation of the Cr phase and the microstructural features are examined during cold rolling. The results are summarized as follows.(1) The dendritic Cr phase in the as-cast Cu-Cr alloy is monocrystal with the 〈110〉 growth direction of dendrite.(2) Each Cr dendrite in the Cu matrix deforms by primary slip probably under the hydrostatic compression stress, and thus the {001} 〈110〉 rolling texture, being typical of bcc monocrystal metals, is formed by the deformation.(3) Cr fibers do not exhibit extensive areas with virtually tangled dislocations, which may be responsible for keeping the ductility of the Cr phase even in the heavily deformed composite (up to rolling strain η=4.51).(4) With increasing η, the Cu matrix spacing decreases faster than that of Cr. However detachment of the Cu matrix from the Cr fiber is not confirmed during cold rolling, with microstructural observations. Thus, the discrepancy between Cu and Cr spacing suggests that plastic flow occurs in the Cu matrix and Cr deformation is promoted under the hydrostatic compression stress.