Abstract
This paper describes a new modification of equal-channel angular extrusion for the “pass-by-pass” semi-continuous (sc-ECAE) processing of lightweight alloys. Sc-ECAE leads to a multifold increase in productivity and decrease in costs, providing a technical basis for the commercialization of severe plastic deformation (SPD) on a large scale with massive volume production. The evolution of the structure and properties are analyzed for an aluminum alloy (AA) 5083 and a magnesium alloy AZ31 as model materials representing, respectively, the structural refinement under severe plastic deformation (SPD) via strain-induced formation of new grain boundaries and via dynamic recrystallization. For the first alloy, the microstructure after sc-ECAE is formed via ultrafine sub-grains, which are further transformed into sub-micrometer grains during post-ECAE rolling. The preliminary solution treatment of AA5083 is an important stabilizing factor for the achievement of high mechanical properties. For the second alloy, optimized sc-ECAE results in a remarkable structural refinement, and a good balance of properties is obtained with a low number of passes. However, additional rolling in the latter case leads to a degradation of the structure and properties.
Highlights
Among the numerous severe plastic deformation (SPD) techniques available [1], equal-channel angular extrusion (ECAE) is the most developed and promising for the fabrication of ultrafine-grained and bulk nanostructured materials
The solution-treated material was naturally aged for 10 days
The main advantage of multi-step semi-continuous ECAE is processing “pass-by-pass” without the need for billet reshaping and reheating. It provides a multifold increase in productivity and decrease in associated costs
Summary
Among the numerous severe plastic deformation (SPD) techniques available [1], equal-channel angular extrusion (ECAE) is the most developed and promising for the fabrication of ultrafine-grained and bulk nanostructured materials. Despite the sufficiently long history of its development, a few shortcomings still remain in the transformation of ECAE into an effective technique for mass production of bulk ultrafine-grained materials. These issues relate to material handling, including billet insertion into the tool, ejection from tool, reshaping, lubrication, and preheating between passes during multi-pass ECAE at room or elevated temperatures. All of these operations are performed in a discontinuous manner, which are both time- and labor-intensive. Known versions of Metals 2019, 9, 1035; doi:10.3390/met9101035 www.mdpi.com/journal/metals
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