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The strength–grain size relationship in ultrafine-grained metals

The strength–grain size relationship in ultrafine-grained metals
The strength–grain size relationship in ultrafine-grained metals
Metals processed by severe plastic deformation (SPD) techniques, such as equal-channel angular pressing (ECAP) and high-pressure torsion (HPT), generally have submicrometer grain sizes. Consequently, they exhibit high strength as expected on the basis of the Hall–Petch (H–P) relationship. Examples of this behavior are discussed using experimental data for Ti, Al, and Ni. These materials typically have grain sizes greater than ~50 nm where softening is not expected. An increase in strength is usually accompanied by a decrease in ductility. However, both high strength and high ductility may be achieved simultaneously by imposing high strain to obtain ultrafine-grain sizes and high fractions of high-angle grain boundaries. This facilitates grain boundary sliding, and an example is presented for a cast Al-7 pct Si alloy processed by HPT. In some materials, SPD may result in a weakening even with a very fine grain size, and this is due to microstructural changes during processing. Examples are presented for an Al-7034 alloy processed by ECAP and a Zn-22 pct Al alloy processed by HPT. In some SPD-processed materials, it is possible that grain boundary segregation and other features are present leading to higher strengths than predicted by the H–P relationship
1073-5623
5827-5838
Balasubramanian, N.
eb9290dd-f0f0-4237-86d1-ff2f46e396af
Langdon, Terence G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Balasubramanian, N.
eb9290dd-f0f0-4237-86d1-ff2f46e396af
Langdon, Terence G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86

Balasubramanian, N. and Langdon, Terence G. (2016) The strength–grain size relationship in ultrafine-grained metals. Metallurgical and Materials Transactions A, 47 (12), 5827-5838. (doi:10.1007/s11661-016-3499-2).

Record type: Article

Abstract

Metals processed by severe plastic deformation (SPD) techniques, such as equal-channel angular pressing (ECAP) and high-pressure torsion (HPT), generally have submicrometer grain sizes. Consequently, they exhibit high strength as expected on the basis of the Hall–Petch (H–P) relationship. Examples of this behavior are discussed using experimental data for Ti, Al, and Ni. These materials typically have grain sizes greater than ~50 nm where softening is not expected. An increase in strength is usually accompanied by a decrease in ductility. However, both high strength and high ductility may be achieved simultaneously by imposing high strain to obtain ultrafine-grain sizes and high fractions of high-angle grain boundaries. This facilitates grain boundary sliding, and an example is presented for a cast Al-7 pct Si alloy processed by HPT. In some materials, SPD may result in a weakening even with a very fine grain size, and this is due to microstructural changes during processing. Examples are presented for an Al-7034 alloy processed by ECAP and a Zn-22 pct Al alloy processed by HPT. In some SPD-processed materials, it is possible that grain boundary segregation and other features are present leading to higher strengths than predicted by the H–P relationship

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Accepted/In Press date: 11 March 2016
e-pub ahead of print date: 11 April 2016
Published date: 1 December 2016
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 402790
URI: https://eprints.soton.ac.uk/id/eprint/402790
ISSN: 1073-5623
PURE UUID: 9cb47567-572b-42b4-8c64-7ca162f30762
ORCID for Terence G. Langdon: ORCID iD orcid.org/0000-0003-3541-9250

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Date deposited: 15 Nov 2016 14:52
Last modified: 15 Aug 2019 05:14

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