An experimental evaluation of a special ECAP die containing two equal arcs of curvature

Experiments were conducted to evaluate the potential for producing a high degree of homogeneity when processing by equal-channel angular pressing (ECAP) using a special split die having a channel angle of 90° but with two equal fillet radii at the outer and inner points of intersection of the two parts of the channel. Using high-purity aluminum, measurements of the Vickers microhardness were recorded over cross-sectional planes after pressing through 1–4 passes. It is shown that there is less homogeneity after 1 or 2 passes by comparison with a conventional ECAP die and after 3 and 4 passes there are narrow regions of higher hardness extending to depths of ∼1 mm along the upper surfaces of the billets. The results demonstrate a die with two equal arcs of curvature is less effective than a conventional ECAP die for producing homogeneity within the billets.

Research highlights
► An experimental ECAP die was constructed having two equal arcs of curvature.
► The experimental die produced less homogeneity than a conventional ECAP die.
► The experimental die led to regions of higher hardness near the upper surfaces.