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Microstructural evolution and superplasticity in an Mg–Gd–Y–Zr alloy after processing by different SPD techniques

Microstructural evolution and superplasticity in an Mg–Gd–Y–Zr alloy after processing by different SPD techniques
Microstructural evolution and superplasticity in an Mg–Gd–Y–Zr alloy after processing by different SPD techniques
Mg–Gd–Y–Zr alloys have attracted much attention recently due to their ability to exhibit stable fine-grained microstructures and their potential superplastic behavior. However, the microstructure and superplasticity of these alloys processed by severe plastic deformation (SPD) methods remain less understood. In this work, the microstructure and superplastic behavior of an Mg–5Gd–4Y–0.4Zr (GW54) alloy were investigated after processing using extrusion and the SPD processes of equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). Microstructural characterization by transmission electron microscopy and electron backscattered diffraction showed that nano-sized grains of ~72±5 nm were obtained after 8 HPT turns whereas the grain sizes were about ~4.6±0.2 and ~2.2±0.2 µm after extrusion and 4 ECAP passes, respectively. Shear punch tests revealed that the optimum temperature for superplasticity is 623 K for the HPT samples and 723 K for the ECAP and extrusion samples, at which the strain rate sensitivities were measured as about 0.42±0.05, 0.46±0.05 and 0.50±0.05 for the extrusion, ECAP and HPT samples, respectively, and the corresponding activation energies were about 117, 101 and 110 kJ/mol for these three processing conditions. These results suggest that grain boundary sliding controlled by grain boundary diffusion is the dominant mechanism of deformation at the optimum temperatures for superplastic flow.
0921-5093
577-585
Alizadeh, R.
8452d2d2-68c1-4a95-840f-8e19855799af
Mahmudi, R.
1e661235-7596-4004-9ace-4c81e6fe9b21
Pereira, P.H.R.
9ee129fd-0e06-482d-990c-971aaf83b1d0
Huang, Y.
9f4df815-51c1-4ee8-ad63-a92bf997103e
Langdon, T.G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Alizadeh, R.
8452d2d2-68c1-4a95-840f-8e19855799af
Mahmudi, R.
1e661235-7596-4004-9ace-4c81e6fe9b21
Pereira, P.H.R.
9ee129fd-0e06-482d-990c-971aaf83b1d0
Huang, Y.
9f4df815-51c1-4ee8-ad63-a92bf997103e
Langdon, T.G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86

Alizadeh, R., Mahmudi, R., Pereira, P.H.R., Huang, Y. and Langdon, T.G. (2017) Microstructural evolution and superplasticity in an Mg–Gd–Y–Zr alloy after processing by different SPD techniques Materials Science and Engineering: A, 682, pp. 577-585. (doi:10.1016/j.msea.2016.11.080).

Record type: Article

Abstract

Mg–Gd–Y–Zr alloys have attracted much attention recently due to their ability to exhibit stable fine-grained microstructures and their potential superplastic behavior. However, the microstructure and superplasticity of these alloys processed by severe plastic deformation (SPD) methods remain less understood. In this work, the microstructure and superplastic behavior of an Mg–5Gd–4Y–0.4Zr (GW54) alloy were investigated after processing using extrusion and the SPD processes of equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). Microstructural characterization by transmission electron microscopy and electron backscattered diffraction showed that nano-sized grains of ~72±5 nm were obtained after 8 HPT turns whereas the grain sizes were about ~4.6±0.2 and ~2.2±0.2 µm after extrusion and 4 ECAP passes, respectively. Shear punch tests revealed that the optimum temperature for superplasticity is 623 K for the HPT samples and 723 K for the ECAP and extrusion samples, at which the strain rate sensitivities were measured as about 0.42±0.05, 0.46±0.05 and 0.50±0.05 for the extrusion, ECAP and HPT samples, respectively, and the corresponding activation energies were about 117, 101 and 110 kJ/mol for these three processing conditions. These results suggest that grain boundary sliding controlled by grain boundary diffusion is the dominant mechanism of deformation at the optimum temperatures for superplastic flow.

Text __filestore.soton.ac.uk_users_yh2a10_mydocuments_Reza-MSE 2017 accepted manuscript.pdf - Accepted Manuscript
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Accepted/In Press date: 23 November 2016
e-pub ahead of print date: 24 November 2016
Published date: 13 January 2017
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 403291
URI: http://eprints.soton.ac.uk/id/eprint/403291
ISSN: 0921-5093
PURE UUID: 5e48179b-4d20-4d14-a0d5-09f3a5572d78
ORCID for Y. Huang: ORCID iD orcid.org/0000-0001-9259-8123
ORCID for T.G. Langdon: ORCID iD orcid.org/0000-0003-3541-9250

Catalogue record

Date deposited: 29 Nov 2016 15:05
Last modified: 03 Oct 2017 16:33

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Contributors

Author: R. Alizadeh
Author: R. Mahmudi
Author: P.H.R. Pereira
Author: Y. Huang ORCID iD
Author: T.G. Langdon ORCID iD

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