Defects in Al-3wt%Cu after High-pressure Torsion Studied by Two-dimensional Doppler Broadening Spectroscopy

High-pressure torsion (HPT) was applied to the structural refinement of an age-hardenable Al-Cu alloy. HPT deformation gives rise to a grain refinement down to sizes of 100 nm and introduces various types of open volume defects. Positron annihilation spectroscopy (PAS), especially the chemical sensitive method of two-dimensional Doppler-broadening spectroscopy (2d-DB), was used for a detailed analysis of the deformation-induced vacancy-type defects and the vacancy-solute interaction. The correlation between microstructure and thermal annealing is discussed. HPT-deformed Al-3wt%Cu shows predominantly deformation-induced positron traps with a strongly reduced copper environment in comparison with the undeformed sample.