Dislocation density within ultrafine grains in severely deformed aluminium was evaluated by the scanning transmission electron microscopy. The values were around 1014m2 in commercial pure aluminium samples with equivalent strain up to 10. The obtained dislocation densities values correspond to strength between 55 and 70MPa according to the Bailey–Hirsch relationship.

Quantification of Internal Dislocation Density using Scanning Transmission Electron Microscopy in Ultrafine Grained Pure Aluminium Fabricated by Severe Plastic Deformation. Y.Miyajima, M.Mitsuhara, S.Hata, H.Nakashima, N.Tsuji: Materials Science and Engineering A, 2010, 528[2], 776-9