Fabrication of nanostructured deoxidized low-phosphorous copper processed by three-layer stack accumulative roll-bonding.

A nanostructured deoxidized low-phosphorous copper (DLPC) was fabricated by three-layer stack accumulative roll-bonding (ARB) process. The microstructural evolution and the variation of mechanical properties with three-layer stack ARB were investigated in detail. It was found that the microstructure has been evolved from a dislocation cell structure to ultrafine grained structure as the number of ARB cycles increases. In addition, the mean spacing of grain boundaries, which was 45 microm in initial material, reduced to 2.1 microm after 1 cycle, 360 nm after 3 cycles, 250 nm after 5 cycles, then 170 nm after 7 cycles, progressively. The fraction of high-angle grain boundaries after 1-cycle ARB was no more than 0.27, but it increased with the number of ARB cycles, and became surprisingly more than 0.7 after 7-cycle ARB. The tensile strength increased with the number of ARB cycles, and then after 7 cycles it reached about 600 MPa, which is about 2.5 times higher than that of the initial material. Therefore, the three-layer stack ARB is very effective for development of ultrafine grains and high strengthening of DLPC alloy.