Effect of Cu content and number of passes on evolution of microstructure and mechanical properties of ECAPed Al/Cu alloys

Equal channel angular pressing (ECAP) is a materials processing method that allows very high strains to be imposed, leading to extreme work hardening and microstructural refinement. Billets of pure aluminum and cast, homogenized Al-2, 3 and 5 wt.\%Cu alloys were successfully processed up to 10 passes at room temperature using ECAP in a die with an internal channel angle of 110 degrees. The imposed strain resulted in a large reduction in the grain size to a submicron level and breakdown of the hard theta phase to the nano size. The tensile test shows that the ultimate tensile and proof strengths increase with number of passes and with copper content while the \%elongation decreases with increase in the number of passes for both pure aluminum and Al-2\%Cu alloy. For Al-3 and 5 wt.\%Cu alloys, the \%elongation decreases after the first pass then increases with more passes. The homogeneity of deformation indicated by microhardness measurements was higher for route A compared with route Bc and increases with the increase of the ECAP number of passes. (C) 2009 Elsevier B.V. All rights reserved