Designing of ECAP parameters based on strain distribution uniformity

Equal Channel Angular Pressing (ECAP) is currently one of the most popular methods for fabricating Ultra-Fine Grained (UFG) materials. In this work, ECAP process has been performed on commercial pure aluminum up to 8 passes by route A. After verification of FEM work, the influences of four die channel angles, three outer corner angles and pass number up to 8 have been analyzed to investigate strain distribution behavior of ECAPed material. Two methods for quantifying the strain homogeneity namely inhomogeneity index (C_i) and standard deviation (S.D.) are compared. It is shown that C_i is not a good candidate for examining the strain distribution uniformity. Moreover, it is suggested that designing of ECAP die geometry to achieve optimum strain distribution homogeneity is more suitable than the optimum effective strain magnitude. The best strain distribution uniformity in the transverse plane is obtained with Φ=60° and Ψ=15° and for the bulk of the sample, Φ=120° and Ψ=15° or 60°, gives the highest strain dispersal uniformity.