Micro-structural evolution subjected to combined tension–torsion deformation for pure copper

A finite element simulation and experiment were conducted to investigate the characteristics of combined tension–torsion (CCT) deformation. According to the simulation results, a very obvious strain gradient distribution develops on the cross-sections of specimens. The equivalent strains obtained by simulation and the incremental theory of plasticity are in good agreement. The experimental results indicate that the micro-structural evolution on the cross-section and longitudinal section act similarly; grains at the edge suffer a higher degree of refinement compared to those in the center, which is consistent with the simulated results. The micro-voids proliferate and grow as the torsion turns increase, but the volume of the voids decreases, and voids tends to aggregate when a critical torsion strain is reached. The EBSD investigation indicates that grains in the processed specimens are mainly small-angle grain boundaries, and the misorientations concentrate between 2° and 10°.