The role of orientation pinning in statically recrystallized oxygen-free high-conductivity copper wire

The role of orientation pinning by neighboring grains on migrating boundaries in a statically recrystallized oxygen-free high-conductivity (OFHC) copper was investigated. Two specimens of heavily drawn OFHC copper wires deformed to true strains of 2.31 and 3.56 were annealed at 170 °C and local orientations were mapped by means of the automated electron backscattered diffraction technique. Inverse pole figures, misorientation distribution functions, and grain boundary misorientations were calculated from local orientation data. In spite of annealing, the microstructure of the low-strain specimen was characterized by elongated grains, similar to the as-deformed structure, whereas the microstructure of the high-strain specimen showed a high fraction of well-defined recrystallized grains. The recrystallized grains consisted of type A grains, which mostly grew laterally with {hkl} 〈100〉 orientations, and type B grains, which generally grew axially with {hkl} 〈111〉 orientations. Type A grains were larger and of higher frequency than type B grains. The large size of Type A grains was attributed to the high frequency of the mobile boundaries with misorientations in the 40 to 50 deg range. Boundaries that were misoriented at 60 deg 〈111〉 (∑3) were found to exert the greatest pinning effect on the growing grains. This caused recrystallized grains to grow either laterally or axially, and sometime led to "branching." A detailed analysis of the influence of the next neighbor misorientations in the perimeter of the recrystallized grains is presented.