The enhancement of strength of a Cu-1.4 mass%Ni-0.25 mass%P-0.1 mass%Zr alloy, in which the Ni and P contents are about twice larger than those in commercial Cu-Ni-P alloys, has been tried by means of combining accumulative roll-bonding (ARB) process by 7 cycles and aging treatment at 350 to 450°C. For the sake of comparison, the mechanical properties of the alloy conventionally cold-rolled to a reduction of 50% and 90% and aged at 350 to 450°C have also been examined. The grain sizes of the Cu-Ni-P-Zr specimens deformed by 7-cycle ARB process and 90% cold-rolling were refined down to about 0.4 μm and 4 μm, respectively, and the fractions of high angle grain-boundaries in the specimens were nearly the same, about 45%. Initial aging, subsequent ARB process or 90% cold-rolling and re-aging at 400°C produced the Cu-Ni-P-Zr alloy highly strengthened. The alloy, initially aged, then ARB-processed and re-aged, had a tensile strength of 780 MPa, an elongation of 6% up to failure and an electrical conductivity of 56% IACS. The differences in yield strength among the re-aged specimens after 50% and 90% cold-rolling and ARB process are explained by the differences among the dislocation density, grain size and inter-precipitate spacing.
