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Parallel tubular channel angular pressing (PTCAP) is a recently developed novel intense plastic deformation method appropriate for fabrication ultrafine-grained and nanostructured cylindrical tubes. In the present work a commercially pure copper was processed via multi-pass PTCAP and the effects of number of passes on grain refinement and the dislocation density were studied. TEM analysis showed that after first pass elongated subgrains with interior tangled dislocations were formed. After pass number two the density of interior dislocations through the elongated grains was decreased. In the next stages of deformation, at pass number three, elongated grains almost disappeared and equiaxed grains with grain size about 150nm are formed as a result of dynamic recovery. The dislocation densities were measured by hardness indentation size effect using the Nix–Gao model. The results showed that increase in …