The microstructure of plastically deformed Al-5.9%Mg-0.3%Sc-0.18%Zr alloy has been
investigated. The severe plastic deformation has been performed by high pressure torsion
straining (HPT) up to 15 revolutions at room temperature. The microstructure as a function of
the number of revolutions is studied by X-ray diffraction peak profile analysis. It is concluded
that the HPT technique results in nanostructure even after 0.5 turn with very high dislocation
density. The crystallite size decreases and the dislocation density increases with the number of
revolutions, however, after five turns they go into saturation. The edge and the dipole
character of the dislocation structure becomes stronger with the increase of the number of
revolutions. The value of the crystallite size determined by X-ray peak profile analysis is a bit
smaller than the grain size obtained by transmission electron microscopy (TEM)
