Analysis of Plastic Deformation and Sample Geometry during the Compression Stage in High-Pressure Torsion
The production of ultrafine-grained metals through severe plastic deformation (SPD) has attracted significant interest in the scientific community due to the improvement in mechanical properties. Among SPD methods, high pressure torsion (HPT) processing is most effective in producing exceptionally small grains in disc-shaped samples subjected to high hydrostatic pressures and concurrent torsional straining. The present paper analyzes the elastic distortions and plastic flow during the application of compressive pressure in samples during HPT. Simulations through finite element method reveal a distortion of the initial shape of the sample and a gradient in sample thickness between the center and the edge due to elastic distortions. Also, it is shown that significant plastic deformation takes place in this stage and this is before any torsional deformation is imposed on the sample.