Enhanced Mechanical and Electrical Properties of a Cu-Ni-Si Alloy by Thermo-mechanical Processing

Two different thermo-mechanical processing routes, single-cold-rolling and double-cold-rolling, are adopted to process a Cu-Ni-Si alloy, and their effects on the microstructure and properties of the alloys are investigated. While keeping identical aging treatments and equivalent total cold-rolling deformation, 45-minute final aging at 450 °C endows the double-cold-rolling-processed alloys with a tensile strength of 754 ± 12 MPa, higher than 691 ± 3 MPa for the single-cold-rolling-processed alloys, whereas their electrical conductivities are close (~ 39 pct IACS). The final aging at 450 °C for 4 hours, on the other hand, renders the double-cold-rolling-processed alloy an electrical conductivity of 52.6 pct IACS, greater than 43.7 pct IACS for the single-cold-rolling-processed alloy, whereas their strengths are approximately identical (~ 705 MPa). The superior mechanical and electrical properties in the double-cold-rolling-processed alloy with the final aging time from 45 minutes to 4 hours are attributed to the dissolution of large precipitates during the second cold rolling followed by the acceleration of fine and uniformly dispersed precipitates in the final aging. Finally, the effects of dislocations, grain boundaries, solute atoms, and precipitates on the mechanical and electrical properties of the examined Cu-Ni-Si alloy are discussed on the theoretical basis, which can provide guidelines to further processing optimization.