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Microhardness and corrosion properties of hypoeutectic Al-7Si alloy processed by high-pressure torsion

Microhardness and corrosion properties of hypoeutectic Al-7Si alloy processed by high-pressure torsion
Microhardness and corrosion properties of hypoeutectic Al-7Si alloy processed by high-pressure torsion
High-pressure torsion (HPT) was used to produce hypoeutectic Al-7Si alloy samples having a range of microstructures to investigate the effect of the grain refinement on its corrosion behaviour in 3.5 wt. % NaCl solution for the first time. Optical microscopy measurements reveal that with the HPT processing increased from 1/4 to 10 revolutions under an applied pressure of 6.0 GPa, brittle coarse silicon particles and intermetallic phases were effectively broken into ultrafine-grained particles and redistributed homogeneously into the Al-rich matrix. Open-circuit potential and polarization curves results exhibit that corrosion resistance of the Al-7Si alloy in NaCl solution was significantly enhanced upon high torsion strains, with corrosion rate reduced from 7.41 ?m y–1 for the as-received sample to 1.68 ?m y–1 for the 10-turn processed sample. Electrochemical impedance spectroscopy analysis combined with characterization of the corroded samples using scanning electron microscopy and energy dispersive X-ray spectroscopy indicates that the enhancement in corrosion performance of the Al-7Si alloy is due to the breakage of coarse silicon particles and intermetallic phases, the microstructure homogeneity and the increased HPT-induced active sites. It is demonstrated that microstructure refinement through HPT processing can significantly improve both microhardness and corrosion properties of the Al-7Si alloy.
Al–7Si alloys, high-pressure torsion, grain refinement, corrosion resistance, microhardness, electrochemical impedance spectroscopy
0261-3069
193-202
Wang, Xue
e67fe3f0-e4a6-46d5-abc4-101b266b1d07
Nie, Mengyan
a8613738-d74a-40fb-8881-08069fb0a34b
Wang, Chuan Ting
80ad9adf-a9df-49ed-934d-fa64505b920d
Wang, S.C.
8a390e2d-6552-4c7c-a88f-25bf9d6986a6
Gao, Nong
9c1370f7-f4a9-4109-8a3a-4089b3baec21
Wang, Xue
e67fe3f0-e4a6-46d5-abc4-101b266b1d07
Nie, Mengyan
a8613738-d74a-40fb-8881-08069fb0a34b
Wang, Chuan Ting
80ad9adf-a9df-49ed-934d-fa64505b920d
Wang, S.C.
8a390e2d-6552-4c7c-a88f-25bf9d6986a6
Gao, Nong
9c1370f7-f4a9-4109-8a3a-4089b3baec21

Wang, Xue, Nie, Mengyan, Wang, Chuan Ting, Wang, S.C. and Gao, Nong (2015) Microhardness and corrosion properties of hypoeutectic Al-7Si alloy processed by high-pressure torsion. Materials & Design, 83, 193-202. (doi:10.1016/j.matdes.2015.06.018).

Record type: Article

Abstract

High-pressure torsion (HPT) was used to produce hypoeutectic Al-7Si alloy samples having a range of microstructures to investigate the effect of the grain refinement on its corrosion behaviour in 3.5 wt. % NaCl solution for the first time. Optical microscopy measurements reveal that with the HPT processing increased from 1/4 to 10 revolutions under an applied pressure of 6.0 GPa, brittle coarse silicon particles and intermetallic phases were effectively broken into ultrafine-grained particles and redistributed homogeneously into the Al-rich matrix. Open-circuit potential and polarization curves results exhibit that corrosion resistance of the Al-7Si alloy in NaCl solution was significantly enhanced upon high torsion strains, with corrosion rate reduced from 7.41 ?m y–1 for the as-received sample to 1.68 ?m y–1 for the 10-turn processed sample. Electrochemical impedance spectroscopy analysis combined with characterization of the corroded samples using scanning electron microscopy and energy dispersive X-ray spectroscopy indicates that the enhancement in corrosion performance of the Al-7Si alloy is due to the breakage of coarse silicon particles and intermetallic phases, the microstructure homogeneity and the increased HPT-induced active sites. It is demonstrated that microstructure refinement through HPT processing can significantly improve both microhardness and corrosion properties of the Al-7Si alloy.

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Accepted/In Press date: 5 June 2015
e-pub ahead of print date: 29 June 2015
Published date: 15 October 2015
Keywords: Al–7Si alloys, high-pressure torsion, grain refinement, corrosion resistance, microhardness, electrochemical impedance spectroscopy
Organisations: nCATS Group

Identifiers

Local EPrints ID: 377785
URI: http://eprints.soton.ac.uk/id/eprint/377785
ISSN: 0261-3069
PURE UUID: af3a4d04-7e06-4ec5-a808-9a36e4b662b1
ORCID for Mengyan Nie: ORCID iD orcid.org/0000-0002-7758-760X
ORCID for Nong Gao: ORCID iD orcid.org/0000-0002-7430-0319

Catalogue record

Date deposited: 18 Jun 2015 11:10
Last modified: 15 Mar 2024 03:10

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Contributors

Author: Xue Wang
Author: Mengyan Nie ORCID iD
Author: Chuan Ting Wang
Author: S.C. Wang
Author: Nong Gao ORCID iD

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