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Microstructure development and hardening during high pressure torsion of commercially pure aluminium: strain reversal experiments and a dislocation based model

Zhang, Jiuwen, Gao, Nong and Starink, Marco J. (2011) Microstructure development and hardening during high pressure torsion of commercially pure aluminium: strain reversal experiments and a dislocation based model Materials Science and Engineering: A, 528, (6), pp. 2581-2591. (doi:10.1016/j.msea.2010.11.079).

Record type: Article

Abstract

The effect of strain reversal on hardening due to high pressure torsion (HPT) was investigated using commercially pure aluminium. Hardening is lower for cyclic HPT (c-HPT) as compared to monotonic HPT (m-HPT). When using a cycle consisting of a rotation of 90 degree per half cycle, there is only a small increase in hardness if the total amount of turns is increased from 1 to 16. Single reversal HPT (sr-HPT) processing involves torsion in one direction followed by a (smaller) torsion in the opposite direction. It is shown that a small reversal of 0.25 turn (90 degree) reduces hardness drastically, and that decrease is most marked for the centre region. These behaviours and other effects are interpreted in terms of the average density of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs). A model is presented that describes the experimental results well. A key element of the model is the assumption that at the very high strains developed in severe plastic deformation processes such as HPT, the dislocation density reaches a saturation value. The model indicates that the strength / hardness is predominantly due to GNDs and SSDs.

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Published date: 15 March 2011
Keywords: severe plastic deformation (spd), aluminium alloys, high pressure torsion, dislocation, hardness
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 168241
URI: http://eprints.soton.ac.uk/id/eprint/168241
ISSN: 0921-5093
PURE UUID: 431eda89-4bcb-4cea-aac8-4dadd28e823f

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Date deposited: 25 Nov 2010 14:29
Last modified: 18 Jul 2017 12:23

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Contributors

Author: Jiuwen Zhang
Author: Nong Gao

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