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An investigation of microstructures and grain-boundary evolution during ECA pressing of pure aluminum

An investigation of microstructures and grain-boundary evolution during ECA pressing of pure aluminum
An investigation of microstructures and grain-boundary evolution during ECA pressing of pure aluminum
High-purity aluminum (99.99 pct) was processed by equal-channel angular pressing (ECAP) at room temperature through a die with a 90 deg angle between the die channels. Samples were examined by transmission electron microscopy (TEM) and orientation imaging microscopy (OIM) methods after one, four, and 12 passes through the die. Repetitively pressed samples were rotated by 90 deg in the same sense between successive pressing operations (route BC). After one pressing, TEM showed a subgrain structure which was elongated in the shearing direction. Corresponding OIM data illustrated an inhomogeneous microstructure in which bandlike features were also aligned with the shearing direction. The lattice orientation varied from location to location in the material. The boundary disorientation distribution determined from the OIM data exhibited a peak at 2 to 5 deg, in agreement with a predominance of subgrains in the microstructure. After four pressings, the microstructure data obtained by TEM and OIM were mutually consistent. The disorientation data revealed a decrease in the population of 2 to 5 deg boundaries accompanied by an overall upward shift in the distribution. Two orientations were generally apparent in the texture, although specific orientations varied with location. Often, a 111 orientation tended to align with the shear direction. Following 12 ECA passes, the grain size was reduced further to about 1.0 ?m. The populations of high-angle boundaries (15 deg) increased in the disorientation distribution. A texture characteristic of shear deformation of fcc metals became apparent, although the orientations and particular components varied with location. Microstructural refinement during severe straining includes the development of large fractions of high-angle boundaries.
1073-5623
2173-2184
Terhune, S.D.
8f5260dc-a493-4776-88b9-3b82766a79c2
Swisher, D.L.
2fcb5129-ce40-4e4c-8930-ec12bf64cd1c
Oh-ishi, K.
35ea2a6a-7c9d-470e-b443-53b60e41dc62
Horita, Z.
84a80017-cbaf-4713-8346-6f69ac7ea63e
Langdon, T.G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
McNelley, T.R.
86e07e47-8710-46a6-bbe9-b34bcd66383b
Terhune, S.D.
8f5260dc-a493-4776-88b9-3b82766a79c2
Swisher, D.L.
2fcb5129-ce40-4e4c-8930-ec12bf64cd1c
Oh-ishi, K.
35ea2a6a-7c9d-470e-b443-53b60e41dc62
Horita, Z.
84a80017-cbaf-4713-8346-6f69ac7ea63e
Langdon, T.G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
McNelley, T.R.
86e07e47-8710-46a6-bbe9-b34bcd66383b

Terhune, S.D., Swisher, D.L., Oh-ishi, K., Horita, Z., Langdon, T.G. and McNelley, T.R. (2002) An investigation of microstructures and grain-boundary evolution during ECA pressing of pure aluminum. Metallurgical and Materials Transactions A, 33 (7), 2173-2184.

Record type: Article

Abstract

High-purity aluminum (99.99 pct) was processed by equal-channel angular pressing (ECAP) at room temperature through a die with a 90 deg angle between the die channels. Samples were examined by transmission electron microscopy (TEM) and orientation imaging microscopy (OIM) methods after one, four, and 12 passes through the die. Repetitively pressed samples were rotated by 90 deg in the same sense between successive pressing operations (route BC). After one pressing, TEM showed a subgrain structure which was elongated in the shearing direction. Corresponding OIM data illustrated an inhomogeneous microstructure in which bandlike features were also aligned with the shearing direction. The lattice orientation varied from location to location in the material. The boundary disorientation distribution determined from the OIM data exhibited a peak at 2 to 5 deg, in agreement with a predominance of subgrains in the microstructure. After four pressings, the microstructure data obtained by TEM and OIM were mutually consistent. The disorientation data revealed a decrease in the population of 2 to 5 deg boundaries accompanied by an overall upward shift in the distribution. Two orientations were generally apparent in the texture, although specific orientations varied with location. Often, a 111 orientation tended to align with the shear direction. Following 12 ECA passes, the grain size was reduced further to about 1.0 ?m. The populations of high-angle boundaries (15 deg) increased in the disorientation distribution. A texture characteristic of shear deformation of fcc metals became apparent, although the orientations and particular components varied with location. Microstructural refinement during severe straining includes the development of large fractions of high-angle boundaries.

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Published date: 2002

Identifiers

Local EPrints ID: 23797
URI: http://eprints.soton.ac.uk/id/eprint/23797
ISSN: 1073-5623
PURE UUID: 3db2ef5f-bf69-4f9b-9bd1-37b45f314eab
ORCID for T.G. Langdon: ORCID iD orcid.org/0000-0003-3541-9250

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Date deposited: 28 Mar 2006
Last modified: 17 Dec 2019 01:49

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Contributors

Author: S.D. Terhune
Author: D.L. Swisher
Author: K. Oh-ishi
Author: Z. Horita
Author: T.G. Langdon ORCID iD
Author: T.R. McNelley

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