To have an insight into the occurrence of inverse Hall-Petch relationship in ultrafine-grained (UFG) aluminum alloys produced by severe plastic deformation (SPD), ultra-SPD (i.e. inducing several ten thousand shear strains via high-pressure torsion, HPT) followed aging is applied to Al-La-Ce alloy. Average nanograin sizes 40 and 80 nm are successfully achieved together with strain-induced Lomer...