J. KLIBER, I. MAMUZI] SELECTED NEW TECHNOLOGIES AND RESEARCH THEMES IN MATERIALS FORMING Received – Prispjelo: 2008-10-24 Accepted – Prihva}eno: 2009-07-10

Cyclic plastic deformation introduced by forging with a rotating lower anvil leads to materials with grain size between 20 and 200 nm, depending on various fac-tors. This severe plastic deformation process known as High Pressure Torsion (HPT) can be used for forming nanopowders in order to refine their microstructure. Me-chanical properties of such products are given by the amount of plastic deformation, i.e. by the total amount of strain 1. Understanding this relationship and the im-pact of repetitive deformation is crucial. It is not only the individual deformation cycles but the plasticity limit as well that play a role in this process. Software simulation is used for modelling laboratory or plant processing prior to its actual application. Figure 1 outlines the prin-ciples of the HTP process. The workpiece is held and compressed between the upper and lower anvils. The lower anvil rotates, thereby exerting shear forces through friction between its surface and the material. Development of the software model was based on dislo-cation structures