Microstructure and mechanical properties of ultrafine grained complex copper alloy fabricated by accumulative roll-bonding process.

Accumulative roll-bonding (ARB) process using dissimilar copper alloys was performed up to six cycles (-an equivalent strain of 4.8) at ambient temperature without lubricant for fabrication of a new complex copper alloy. The dissimilar copper alloy sheets of oxygen free copper (OFC) and dioxide low-phosphorous copper (DLPC) with thickness of 1 mm were degreased and wire-brushed for the ARB process. The sheets were then stacked together and rolled by 50% reduction so that the thickness became 1 mm again. The sheet was then cut to the two pieces of same length and the same procedure was repeated up to six cycles. A new sound complex copper alloy sheet in which OFC and DLPC are combined each other was successfully fabricated by the ARB process. The tensile strength of the copper alloy increased with increasing the number of ARB cycles, reached 492 MPa after six cycles, which is about three times of the initial material. The average grain size was 12.6 μm after the 1st cycle, but it became 1.5 μm after six cycles. Microstructures and mechanical properties of the complex copper alloy fabricated by the ARB were investigated in detail.