An oxygen free high conductivity (OFHC) copper was subjected to maximum 13 ECAP passes to achieve a sufficiently high degree of deformation. Strength properties (yield stress and ultimate tensile strength) show obvious increase up to the 4 th pass. In the 6 th ECAP pass, the yield stress and ultimate tensile strength are stabilized at a maximum of 449 MPa. Microstructure studies showed that the 1 st ECAP pass caused a significant increase of dislocation density. These dislocations are arranged in cells, forming dense dislocation walls at low-angle subgrains. After the 5 th ECAP pass, well-defined equiaxed ultrafine grains of diameter approximately 500 nm had emerged forming high-angle grain boundaries. The defect density studies carried out by positron annihilation spectroscopy method revealed an increase in a defect density (vacancies, dislocations) up to the 4 th pass, consequently with number of ECAP passes increasing, decrease in defects density (seen by positrons) was observed.K e y w o r d s : dislocation, grain boundaries, equiaxed ultrafine grained microstructure, electron microscopy, Equal Channel Angular Pressing (ECAP)

In the paper, calculation of the ductile fracture criteria for experimental materials as HSLA (high strength low alloy) steel, aluminium alloy EN AW 6082 T6 and powder metallurgy material ALUMIX 321 was carried out. Using ring and compression tests, it was possible to determine friction coefficient, stress-strain curves, constants for the Hollomon's equation, material workability and nCL (normalized Cockcroft-Latham) criteria. Moreover, the results from the nCL criteria calculations obtained from compression tests and numerical simulations were compared and verified. Numerical simulations were done by the Deform 3D software. It was confirmed that both methods provide similar results.