Annealing behavior and recrystallized texture in ARB processed copper

The recrystallization behavior and texture development in copper accumulative roll-bonding (ARB) processed by various cycles (2, 4 and 6 cycle) were studied by differential scanning calorimetry (DSC) analysis and SEM/EBSP method. The exothermic peaks caused by recrystallization appeared at 210 similar to 253 degrees C in each sample. The peak positions shifted to lower temperature as the number of ARB cycles increased. This result indicated that the evolution of finer microstructure with increasing number of the ARB cycles enhanced the occurrence of recrystallization at lower temperature. The stored energy calculated from the DSC curve of the ARB processed copper increased with the increasing strains. During an annealing, the preferential growth of cube-oriented grains ({100}< 001 >) occurred in each sample. The recystallization behavior of ARB processed copper having low stacking fault energies was distinguished from that of so-called "recovery type" materials, i.e. aluminum and low carbon steels, which shows rather continuous changes in microstructure during annealing. The accumulated strains provided the driving force for the preferential growth, which was the same mechanism as the preferential growth in normally rolled copper. The sharpest cube texture developed in ARB processed copper by 4 cycles. The difference of cube texture development between 2 cycles and 4 cycles was caused by the distribution of cube-oriented regions which corresponded to the nucleation sites of recrystallized grains before annealing. More nanocystalline layers in the vicinity of bonded interfaces were distributed in ARB processed copper by 6 cycles than 4cycles. The nanocystalline structure could grow faster than the cube-oriented grains and led to the inhibition of sharp cube texture in the ARB processed copper by 6 cycles.