Microstructure evolution in copper under severe plastic deformation detected by in situ X-ray diffraction using monochromatic synchrotron light

Microstructure evolution in severely deformed Cu has been investigated using high-energy synchrotron light during in situ high-pressure torsion (HPT) at room temperature. Relative changes in broadening of Bragg peaks and crystal lattice expansion were studied in the loading-unloading regime of torsion straining. Experimental results revealed fast relaxation (on the order of hundred of seconds) that occurred due to annihilation of HPT-induced crystal lattice defects, which were generated directly during deformation. The kinetics of relaxation is probably diffusion-controlled; therefore, the enhanced diffusivity can be explained by extremely high excess vacancy concentration, which is usually achieved at thermal equilibrium near the melting point. (C) 2008 Elsevier B.V. All rights reserved.