The microstructure of f.c.c. metals (Al, Cu, Ni) and alloys (Al-Mg) processed by severe
plastic deformation (SPD) methods is studied by X-ray diffraction line profile analysis. It is
shown that the crystallite size and the dislocation density saturate with increasing strain.
Furthermore, the Mg addition promotes efficiently a reduction of the crystallite size and an
increase of the dislocation density in Al during the SPD process. The yield strength correlates
well with that calculated from the dislocation density using the Taylor equation, thereby
indicating that the main strengthening mechanism in both pure metals and alloys is the
interaction between dislocations