Copper specimens were severely deformed by equal channel angular pressing up to 8 passes. The microstructure was studied by X-ray diffraction peak profile analysis as a function of strain. It was found that the crystallite size was already reduced to a few tens of nm at a strain of 0.7 and it did not change significantly during further deformation. At the same time, the dislocation density increased gradually up to a strain of 4. The dipole character of the dislocation structure became stronger with increasing strain. The thermal stability of the microstructure was examined by differential scanning calorimetry. The temperature of the differential scanning calorimetry peak related to the recovery of the microstructure decreased with increasing strain. At the beginning of the heat release, a bimodal grain structure develops indicated by a special double-peak shape of the diffraction line profiles.

Dislocation Structure and Crystallite Size in Severely Deformed Copper by X-Ray Peak Profile Analysis. J.Gubicza, L.Balogh, R.J.Hellmig, Y.Estrin, T.Ungár: Materials Science and Engineering A, 2005, 400-401, 334-8