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°. The imposed strain resulted in a large reduction in the grain size to a submicron level and breakdown of the hard θ 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.