Improving homogeneity of ultrafine-grained/nanostructured materials produced by ECAP using a bevel-edge punch

A new geometrical parameter, lambda (λ) angle, was introduced in the equal-channel angular pressing (ECAP) process. The clockwise angle between the theoretical shear plane and the punch/billet interface was defined as λ. Microhardness homogeneity was increased employing λ = 90° compared to the conventional technique with the horizontal punch tip (λ = 45°). The main reason was reducing the width of the plastic deformation zone (PDZ) and occurring the deformation in the immediate vicinity of the shear plane. The imposed shear strain became uniform by decreasing the width of PDZ, leading to homogeneous microstructure and properties. In addition, microstructural assessment showed that the second phase particles and constitutive elements were uniformly distributed in case of λ = 90°. More uniform microstructure was also achieved in this case. Furthermore, tensile tests showed that ductility of the billets after one and two ECAP passes using λ = 90° was increased by around 36 and 21 %, respectively.