Influence of the pre-homogenization treatment on the microstructure evolution and the mechanical properties of Al-Cu alloys processed by ECAP

Equal channel angular pressing (ECAP) is a material processing method that allows very high strains to be imposed, leading to extreme work hardening and microstructural refinement. Billets of nonhomogenized (ascast) and homogenized Al-2 and 3. wt.%Cu alloys were successfully processed by ECAP up to different number of passes at room temperature. The microstructure was evaluated into ultrafine grained (UFG) microstructure with high grain boundary misorientation angle in the case of Al-Cu homogenized and nonhomogenized alloys due to imposed strain resulted. It was observed that more homogenized microstructures with smaller grain sizes and higher values of high grain boundary misorientation angle were obtained in the case of homogenized alloys. Higher improvement in the tensile properties and the microhardness values was noted in the case of Al-Cu homogenized alloys. The elongation% and uniform elongation% were observed to decrease with increase of the number of passes for all of the Al-Cu alloys except in the case of Al-3%Cu homogenized alloy. In the case of Al-3. wt.%Cu alloy, the elongation% and uniform elongation% were decrease after the second pass then it increases with the addition of more passes. The microhardness distribution and the deformation homogeneity across the transverse direction of the billet were measured. The homogeneity of deformation was observed to increase with the increase of the ECAP number of passes and the copper content. Higher degree of the homogeneity of deformation was observed in the case of the homogenized alloys comparing to that in the case of the nonhomogenized alloys.