Influence of Al2O3 nanoparticles on the thermal stability of ultra-fine grained copper prepared by high pressure torsion

Ultra-fine grained (UFG) Cu (grain size 80 nm) containing 0.5 wt.% Al2O3 nanoparticles (size 20nm) was prepared by high pressure torsion (HPT). Positron lifetime spectroscopy was employed to characterize the microstructure of this material, especially with respect to types and concentration of lattice defects. The evolution of microstructure with increasing temperature was studied by positron lifetime spectroscopy and X-ray diffraction measurements. The thermal stability of the Cu + 0.5 wt.% Al2O3 nanocomposite was compared with that of pure UFG Cu prepared by the same technique. The processes taking place during thermal recovery of the initial nanoscale structure in both studied materials are described.