Evolution of microstructures and texture in the surface layer of copper during burnishing process

The evolution of microstructures and texture subjected to a burnishing process in pure copper was investigated by transmission electron microscopy and electron backscattered diffraction. The grains of the top surface underwent significant refinement with a minimum grain size of ∼100 nm. The grain refinement was dominated by dislocation activities, including formation of dislocation cells, transformation of cell walls into sub-grain boundaries, development of highly disoriented sub-boundaries and generation of equiaxed grains. Shear strain induced by friction affected the strain state at the first pass of burnishing, resulting in a {001}<110> shear texture. Brass orientation developed well at the early stage of burnishing. Then, with a further increase in plastic strain, Brass orientation decreased, while the Goss orientation was observed, which mainly owing to the transformation from Brass to Goss orientation by rotation along the α-fibre. Moreover, dynamic recrystallisation occurred as the strain increased.