Solute segregation induced sandwich structure in Al-Cu(-Au) alloys

Yunhe Zheng, Yixian Liu, Nick Wilson, Shiqi Liu, Xiaojun Zhao, Houwen Chen, Jinfeng Li, Ziqiao Zheng, Laure Bourgeois, Jian Feng Nie

Research output: Contribution to journalArticleResearchpeer-review

Abstract

In this work atomic-resolution techniques of high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDXS)-STEM and first-principles calculations have been combined to study a hitherto unreported sandwich structure formed in aged samples of Al-Cu and Al-Cu-Au alloys. This sandwich structure comprises a stack of regularly spaced plates of metastable precipitate phases of GP zones, θ″ and θ′. Within the sandwich structure, the separation between the broad surface of θ′ and its adjacent GP zone, as well as that between two neighbouring GP zones, is always three {002}α planes. This sandwich structure is observed for θ′ precipitates of various thicknesses. Based on experimental results and calculations, it is inferred that the formation of the sandwich structure is induced by the θ′/Al interfacial segregation of Cu atoms, rather than the misfit associated with θ′ formation. In the sandwich structure formed in the ternary alloy, Au atoms distribute mainly in the central part of θ′ plate, but not at the θ′/Al interface or in the GP zone. Calculations confirm the experimental observations and further indicate that, energetically, Au atoms prefer to substitute for Cu, rather than Al, atoms within θ′.

Original languageEnglish
Pages (from-to)17-29
Number of pages13
JournalActa Materialia
Volume184
DOIs
Publication statusPublished - 1 Feb 2020

Keywords

  • Aluminium alloys
  • Density functional theory
  • Precipitation
  • Scanning transmission electron microscopy

Cite this

Zheng, Yunhe ; Liu, Yixian ; Wilson, Nick ; Liu, Shiqi ; Zhao, Xiaojun ; Chen, Houwen ; Li, Jinfeng ; Zheng, Ziqiao ; Bourgeois, Laure ; Nie, Jian Feng. / Solute segregation induced sandwich structure in Al-Cu(-Au) alloys. In: Acta Materialia. 2020 ; Vol. 184. pp. 17-29.
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abstract = "In this work atomic-resolution techniques of high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDXS)-STEM and first-principles calculations have been combined to study a hitherto unreported sandwich structure formed in aged samples of Al-Cu and Al-Cu-Au alloys. This sandwich structure comprises a stack of regularly spaced plates of metastable precipitate phases of GP zones, θ″ and θ′. Within the sandwich structure, the separation between the broad surface of θ′ and its adjacent GP zone, as well as that between two neighbouring GP zones, is always three {002}α planes. This sandwich structure is observed for θ′ precipitates of various thicknesses. Based on experimental results and calculations, it is inferred that the formation of the sandwich structure is induced by the θ′/Al interfacial segregation of Cu atoms, rather than the misfit associated with θ′ formation. In the sandwich structure formed in the ternary alloy, Au atoms distribute mainly in the central part of θ′ plate, but not at the θ′/Al interface or in the GP zone. Calculations confirm the experimental observations and further indicate that, energetically, Au atoms prefer to substitute for Cu, rather than Al, atoms within θ′.",
keywords = "Aluminium alloys, Density functional theory, Precipitation, Scanning transmission electron microscopy",
author = "Yunhe Zheng and Yixian Liu and Nick Wilson and Shiqi Liu and Xiaojun Zhao and Houwen Chen and Jinfeng Li and Ziqiao Zheng and Laure Bourgeois and Nie, {Jian Feng}",
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Zheng, Y, Liu, Y, Wilson, N, Liu, S, Zhao, X, Chen, H, Li, J, Zheng, Z, Bourgeois, L & Nie, JF 2020, 'Solute segregation induced sandwich structure in Al-Cu(-Au) alloys', Acta Materialia, vol. 184, pp. 17-29. https://doi.org/10.1016/j.actamat.2019.11.011

Solute segregation induced sandwich structure in Al-Cu(-Au) alloys. / Zheng, Yunhe; Liu, Yixian; Wilson, Nick; Liu, Shiqi; Zhao, Xiaojun; Chen, Houwen; Li, Jinfeng; Zheng, Ziqiao; Bourgeois, Laure; Nie, Jian Feng.

In: Acta Materialia, Vol. 184, 01.02.2020, p. 17-29.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Solute segregation induced sandwich structure in Al-Cu(-Au) alloys

AU - Zheng, Yunhe

AU - Liu, Yixian

AU - Wilson, Nick

AU - Liu, Shiqi

AU - Zhao, Xiaojun

AU - Chen, Houwen

AU - Li, Jinfeng

AU - Zheng, Ziqiao

AU - Bourgeois, Laure

AU - Nie, Jian Feng

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AB - In this work atomic-resolution techniques of high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDXS)-STEM and first-principles calculations have been combined to study a hitherto unreported sandwich structure formed in aged samples of Al-Cu and Al-Cu-Au alloys. This sandwich structure comprises a stack of regularly spaced plates of metastable precipitate phases of GP zones, θ″ and θ′. Within the sandwich structure, the separation between the broad surface of θ′ and its adjacent GP zone, as well as that between two neighbouring GP zones, is always three {002}α planes. This sandwich structure is observed for θ′ precipitates of various thicknesses. Based on experimental results and calculations, it is inferred that the formation of the sandwich structure is induced by the θ′/Al interfacial segregation of Cu atoms, rather than the misfit associated with θ′ formation. In the sandwich structure formed in the ternary alloy, Au atoms distribute mainly in the central part of θ′ plate, but not at the θ′/Al interface or in the GP zone. Calculations confirm the experimental observations and further indicate that, energetically, Au atoms prefer to substitute for Cu, rather than Al, atoms within θ′.

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KW - Density functional theory

KW - Precipitation

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