Microstructure evolution and mechanical performance of copper processed by equal channel angular rolling

Ultrafine-grained (UFG) oxygen free high conductivity (OFHC) Cu samples were processed by severe plastic deformation (SPD) using the method of equal channel angular rolling (ECAR) up to 33 passes at room temperature. It was found that the grain size gradually decreased from similar to 40 mu m to similar to 250 nm with increasing the number of passes. A maximum dislocation density of similar to 21 x 10(14) m(-2) was achieved after 13 passes of ECAR. For large numbers of passes (between 23 and 33), the dislocation density decreased to similar to 14 x 10(14) m(-2). The proof stress was saturated at the value of about 400 MPa. The stored energy was measured by calorimetry and compared with the values calculated from the parameters of the microstructure. The reduction of the released heat after 13 and 33 passes suggested structural relaxation of the UFG microstructure. For these numbers of passes, the reduction of area in tensile testing was improved without decreasing the proof stress. The correlation between the microstructure and the mechanical behavior was discussed in detail. It was found that ECAR is capable for the mass-production of UFG metallic materials with high strength, therefore this method is a possible way of commercialization of SPD-processed materials.