Characterization of defect microstructure in MgRE (RE=Ce, Nd) alloys after processing by high-pressure torsion using positron annihilation spectroscopy and a high resolution X-ray diffraction
Characterization of defect microstructure in MgRE (RE=Ce, Nd) alloys after processing by high-pressure torsion using positron annihilation spectroscopy and a high resolution X-ray diffraction
Two MgRE (RE=Ce, Nd) alloys with ultrafine-grain (UFG) microstructures were prepared by high-pressure torsion (HPT) at room temperature. The in-depth distribution of defects was characterized by Doppler broadening –variable energy positron annihilation spectroscopy (DBVEPAS). The characteristic S parameter increases in bulk after HPT processing relative to an as-received sample and shows a relative stability between ½ and 10 turns, which suggests a rise in the open volume defect density. However, a theoretical analysis of the S(E) depth profile reveals an increase in the positron diffusion length from ~115 nm for the as-received state to ~207 nm after 10 HPT turns. Almost all the open volume defect consisted of dislocations (positron lifetime of τ = 260 ps). The dislocation density deduced from high-resolution X-ray diffraction in the HPT disc radial direction was reasonably homogeneous (around 4-6 ×1014m-2).
HPT, MG, dislocations, positron, rare earth, spectroscopy, Spectroscopy, Mg, Rare earth, Dislocations, Positron
Bibimounea, I.
73fc0fe0-8029-487d-a726-57fe552d127a
Bourezg, Yousf Islem
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Abib, Khadidja
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Liedke, M.O.
673c17f4-2c76-4863-8f62-bb1c34833e69
Wagner, A.
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Matej, Z.
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Huang, Y.I.
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Langdon, Terence G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Bradai, D.
dfc10bba-9e86-4e1d-b8fe-17c109d5f9fd
15 August 2023
Bibimounea, I.
73fc0fe0-8029-487d-a726-57fe552d127a
Bourezg, Yousf Islem
aab04bbc-d0f1-4ef4-8bef-2471dbbca4f0
Abib, Khadidja
9cba6ab2-87e6-449f-88c1-2ee212117066
Liedke, M.O.
673c17f4-2c76-4863-8f62-bb1c34833e69
Wagner, A.
8437011e-aa5e-4bde-8d31-1c39a1b1179b
Matej, Z.
71d23cc1-ca80-4fd0-8311-343892bf6788
Huang, Y.I.
9f4df815-51c1-4ee8-ad63-a92bf997103e
Langdon, Terence G.
86e69b4f-e16d-4830-bf8a-5a9c11f0de86
Bradai, D.
dfc10bba-9e86-4e1d-b8fe-17c109d5f9fd
Bibimounea, I., Bourezg, Yousf Islem, Abib, Khadidja, Liedke, M.O., Wagner, A., Matej, Z., Huang, Y.I., Langdon, Terence G. and Bradai, D.
(2023)
Characterization of defect microstructure in MgRE (RE=Ce, Nd) alloys after processing by high-pressure torsion using positron annihilation spectroscopy and a high resolution X-ray diffraction.
Physica B: Condensed Matter, 663, [414963].
(doi:10.1016/j.physb.2023.414963).
Abstract
Two MgRE (RE=Ce, Nd) alloys with ultrafine-grain (UFG) microstructures were prepared by high-pressure torsion (HPT) at room temperature. The in-depth distribution of defects was characterized by Doppler broadening –variable energy positron annihilation spectroscopy (DBVEPAS). The characteristic S parameter increases in bulk after HPT processing relative to an as-received sample and shows a relative stability between ½ and 10 turns, which suggests a rise in the open volume defect density. However, a theoretical analysis of the S(E) depth profile reveals an increase in the positron diffusion length from ~115 nm for the as-received state to ~207 nm after 10 HPT turns. Almost all the open volume defect consisted of dislocations (positron lifetime of τ = 260 ps). The dislocation density deduced from high-resolution X-ray diffraction in the HPT disc radial direction was reasonably homogeneous (around 4-6 ×1014m-2).
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Djamel-Bibimoune _PHYSB-D-23-00606_accepted
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Accepted/In Press date: 7 May 2023
e-pub ahead of print date: 19 May 2023
Published date: 15 August 2023
Additional Information:
Funding Information:
The PAS measurements were conducted at the Institute of Radiation Physics at Helmholtz-Zentrum Dresden Rossendorf (HZDR). The SPONSOR (Slow POsitroN System Of Rossendorf) at HZDR [15] and a conventional lifetime spectrometer were used. Positron energies E from the SPONSOR beam varied between 0.03 and 35 keV.
Publisher Copyright:
© 2023 Elsevier B.V.
Keywords:
HPT, MG, dislocations, positron, rare earth, spectroscopy, Spectroscopy, Mg, Rare earth, Dislocations, Positron
Identifiers
Local EPrints ID: 477348
URI: http://eprints.soton.ac.uk/id/eprint/477348
ISSN: 0921-4526
PURE UUID: 005d9c8a-cc03-4c79-bc56-8a7f90c4e052
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Date deposited: 05 Jun 2023 16:41
Last modified: 17 Mar 2024 03:25
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Contributors
Author:
I. Bibimounea
Author:
Yousf Islem Bourezg
Author:
Khadidja Abib
Author:
M.O. Liedke
Author:
A. Wagner
Author:
Z. Matej
Author:
Y.I. Huang
Author:
D. Bradai
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