Equal-Channel Angular Extrusion (ECAE): From a Laboratory Curiosity to an Industrial Technology

Abstract

This paper presents a state-of-the-art and a retrospective view of the critical stages in the evolution of equal-channel angular extrusion (ECAE) from the original idea to a cost-effective industrial technology. These stages include optimization of the structure modification and material processing, development of the special tools, process commercialization, and a large-scale validation of the semi-continuous ECAE at the industrial floor. All aspects are extensively summarized, based on the author’s experience in the field, which spans almost half of a century. Special attention is paid to the processing of large batch billets. Practical examples illustrate industrial applications of ECAE. The scope for future development is also discussed.

Effects of equal channel angular pressing and heat treatments on the microstructures and mechanical properties of selective laser melted and cast AlSi10Mg alloys

“…However, there is still limited information regarding the microstructural evolution and mechanical properties of SLM-fabricated parts subjected to equal channel angular pressing (ECAP). This technique is especially attractive because it is suitable for reasonably sized specimen and according to Segal's work [12] can be scaled-up relatively easily to produce bulk (plate billets of the size 610 × 610 × 100 mm and a weight of 100 kg) ultra-finegrained materials that can be used for a wide range of structural applications. According to Valiev and Langdon [13] during ECAP a sample is pressed through a die composed of two channels with identical cross sections, which intersect one another at a designated angle (typically 90° or 120°).…”

Facing the Issues of Sheet Metal Equal‐Channel Angular Pressing: A Modified Approach Using Stacks to Produce Ultrafine‐Grained High Ductility AA5083 Sheets

“…The die, described in greater detail in the study by Frint et al, [ 4 ] fulfills the criteria for optimum ECAP processing as defined by Segal. [ 2 ] For example, it allows for the application of a sufficient back pressure, which is a key requirement for the introduction of a homogeneous shear deformation in ECAP of bulk materials. Moreover, the die has a large channel cross section of 50 × 50 mm 2 , which in the context of this study facilitates processing of multiple sheets using the stacked sheets approach described above.…”

Large and Severe Plastic Deformation of Metals: Similarities and Differences in Flow Mechanics and Structure Formation

“…The complex loading processes leading to nonmonotonic deformation are characterized by the orientation of the principal axes of the stress and strain‐rate tensors varying with respect to the fibers of the material under deformation. To such processes refer, in addition to ECAP, [ 2,8 ] also such SPD processes as HPT, [ 1,11 ] twist extrusion, [ 12 ] etc. Their characteristic feature is cyclic recurrence, i.e., the dimensions of a billet almost return to their original values in the process.…”

“…As the channels intersect, the direction of the flow velocity vector changes. Segal in various studies [ 8,14,15 ] used the notion of the direct flow lines of material points, parallel to the axes of the intersecting channels. At the bisector of the channels’ intersection angle, the flow velocity varies in a jump‐like manner to a value of Δ V , but in this notion of flow, there will be singular growth of the angular rotation velocity at the bisector, Δ V / δ → ∞, as δ = 0, which would inevitably have a drastic effect on the metal's state.…”

“…It has an effect on grain boundary misorientations and makes a considerable contribution into the total strain of a rod, [ 7 ] which can be several times higher than the strain derived from the formula for simple shear. [ 8 ]…”