Development of a high-strength high-conductivity Cu-Ni-P alloy. Part II: Processing by severe deformation

Deformation microstructures during large-strain plastic working were studied in the pure Cu and Cu-1.5%Ni-0.3%P alloy, the original microstructures of which have been detailed in our companion publication. Microstructural changes depended significantly on the initial structural state. Solution-treated and low-temperature (400°C) aged samples were characterized by rapid strain hardening with early deformation followed by steady-state-like behavior at large strains. Such a rapid increase in hardness might be responsible for the development of deformation twinning and microshear banding at relatively small strains. Deformation textures in these samples were associated with a large fraction of brass orientation, i.e., (011}〈211〉. On the other hand, the samples aged at elevated temperature (600°C) showed gradual continuous strain hardening upon cold working within the studied strain range. Twinning and microshearing were remarkably delayed, and the texture had no unique preferential orientation. After severe deformation, the samples aged at 600°C demonstrated hardness of ∼2500 MPa and electroconductivity >50% IACS.