Analysis of the billet deformation behaviour in equal channel angular extrusion

Jacob R. Bowen, A. Gholinia, S.M. Roberts, P.B. Prangnell

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Equal channel angular extrusion is a relatively novel method for deforming materials to very high plastic strains, with no net
change in the billet’s shape. However, before the technique can be exploited it is important to understand the deformation
behaviour within the die and its relationship to the tooling configuration and friction conditions. Billets containing scribed grids,
simple finite element analysis, and microstructural evidence have been used to investigate this issue. It has been found that the
strain achieved is sensitive to the die angle, friction conditions, and the application of a back-pressure, all of which can have a
large effect on the microstructure and strain inhomogeneity within the processed billet. The distribution of strain is most uniform,
and approximates most closely to a simple shear, if the deformation zone is constrained to be as narrow as possible. The best
processing conditions appear to be obtained with a sharp die corner, low friction, and a constraining back-pressure. Embedded
marker wire experiments have shown that on repeatedly extruding a billet with a constant strain path rotation of material occurs
around the billet’s ends. This results in the sheared billet wrapping around on itself during the process and thus maintaining the
billet’s shape, despite the increasing shear strain in each extrusion cycle. © 2000 Elsevier Science S.A. All rights reserved.
Original languageEnglish
JournalMaterials Science and Engineering: A - Structural Materials: Properties, Microstructure and Processing
Volume287
Pages (from-to)87-99
ISSN0921-5093
DOIs
Publication statusPublished - 2000
Externally publishedYes

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