Equivalent strain distribution at high pressure torsion extrusion of pure copper: Finite element modeling and experimental validation

Results of finite element modeling of strain state of the sample were experimentally validated using copper samples with aluminum markers and analyzed for a deep understanding of the influence of processing parameters and materials properties on the strain distribution in the billets processed by high pressure torsion extrusion (HPTE). Calculations were carried out for pure copper for HPTE regimes with resulting strain in a range between 0.9 and 12.0 at deformation temperatures of 25 and 100 °C. It was established that the accumulated strain in HPTE can be as high as ∼1.5 even at the axis of the sample, which shows the high efficiency of HPTE as a method of severe plastic deformation. A comparison of the calculated strain distributions with experimentally measured ones in copper billets made it possible to reveal the spreading of the deformation zone along the height of the sample, caused by its slippage in the die. It was established that this slippage increases with increasing of deformation temperature and with the value of accumulated strain. X-ray tomography was used to visualize the change of the shape of wire markers inserted in the samples prior to HPTE processing.