The magic thicknesses of θ′ precipitates in Sn-microalloyed Al-Cu

Laure Bourgeois, Christian Dwyer, Matthew Weyland, Jian Feng Nie, Barrington C. Muddle

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

θ′ is an effective strengthening precipitate phase in high-strength Al alloys; unfortunately its nucleation is difficult and usually requires assistance, such as that provided by Sn in Sn-microalloyed Al-Cu. In order to clarify the mechanisms by which Sn promotes the nucleation of θ′, we investigated the structure and thickness of θ′ precipitates in a Al-1.7 at.% Cu alloy with trace additions of Sn (0.01 at.%). Scanning transmission electron microscopy imaging reveals that θ′ platelets recently nucleated at 160 and 200 °C exhibit a discrete distribution of specific, or "magic", thicknesses, corresponding to minima in the residual volumetric and shape misfit strain. This observation is unique to the Sn-assisted nucleation of θ′: θ′ platelets that undergo growth or form in the Sn-free alloy do not display this discrete distribution, although preference for the magic thicknesses persists. Direct evidence is presented that Sn does not accommodate volumetric misfit strain. Instead, it is shown that Sn in its solute form reduces either the interfacial energy of θ′ and/or the transformation shape strain associated with thicknesses intermediate to the magic thicknesses.

Original languageEnglish (US)
Pages (from-to)633-644
Number of pages12
JournalActa Materialia
Volume60
Issue number2
DOIs
StatePublished - Jan 2012
Externally publishedYes

Fingerprint

Precipitates
Nucleation
Platelets
High strength alloys
Strengthening (metal)
Interfacial energy
Transmission electron microscopy
Imaging techniques
Scanning electron microscopy

Keywords

  • Aluminium alloys
  • Heterogeneous nucleation
  • High-angle annular dark field (HAADF)
  • Precipitation

ASJC Scopus subject areas

  • Ceramics and Composites
  • Metals and Alloys
  • Polymers and Plastics
  • Electronic, Optical and Magnetic Materials

Cite this

The magic thicknesses of θ′ precipitates in Sn-microalloyed Al-Cu. / Bourgeois, Laure; Dwyer, Christian; Weyland, Matthew; Nie, Jian Feng; Muddle, Barrington C.

In: Acta Materialia, Vol. 60, No. 2, 01.2012, p. 633-644.

Research output: Contribution to journalArticle

Bourgeois, Laure ; Dwyer, Christian ; Weyland, Matthew ; Nie, Jian Feng ; Muddle, Barrington C. / The magic thicknesses of θ′ precipitates in Sn-microalloyed Al-Cu. In: Acta Materialia. 2012 ; Vol. 60, No. 2. pp. 633-644.
@article{291b4b5775a24863a8e5cd4f47f45c29,
title = "The magic thicknesses of θ′ precipitates in Sn-microalloyed Al-Cu",
abstract = "θ′ is an effective strengthening precipitate phase in high-strength Al alloys; unfortunately its nucleation is difficult and usually requires assistance, such as that provided by Sn in Sn-microalloyed Al-Cu. In order to clarify the mechanisms by which Sn promotes the nucleation of θ′, we investigated the structure and thickness of θ′ precipitates in a Al-1.7 at.{\%} Cu alloy with trace additions of Sn (0.01 at.{\%}). Scanning transmission electron microscopy imaging reveals that θ′ platelets recently nucleated at 160 and 200 °C exhibit a discrete distribution of specific, or {"}magic{"}, thicknesses, corresponding to minima in the residual volumetric and shape misfit strain. This observation is unique to the Sn-assisted nucleation of θ′: θ′ platelets that undergo growth or form in the Sn-free alloy do not display this discrete distribution, although preference for the magic thicknesses persists. Direct evidence is presented that Sn does not accommodate volumetric misfit strain. Instead, it is shown that Sn in its solute form reduces either the interfacial energy of θ′ and/or the transformation shape strain associated with thicknesses intermediate to the magic thicknesses.",
keywords = "Aluminium alloys, Heterogeneous nucleation, High-angle annular dark field (HAADF), Precipitation",
author = "Laure Bourgeois and Christian Dwyer and Matthew Weyland and Nie, {Jian Feng} and Muddle, {Barrington C.}",
year = "2012",
month = "1",
doi = "10.1016/j.actamat.2011.10.015",
language = "English (US)",
volume = "60",
pages = "633--644",
journal = "Acta Materialia",
issn = "1359-6454",
publisher = "Elsevier Limited",
number = "2",

}

TY - JOUR

T1 - The magic thicknesses of θ′ precipitates in Sn-microalloyed Al-Cu

AU - Bourgeois, Laure

AU - Dwyer, Christian

AU - Weyland, Matthew

AU - Nie, Jian Feng

AU - Muddle, Barrington C.

PY - 2012/1

Y1 - 2012/1

N2 - θ′ is an effective strengthening precipitate phase in high-strength Al alloys; unfortunately its nucleation is difficult and usually requires assistance, such as that provided by Sn in Sn-microalloyed Al-Cu. In order to clarify the mechanisms by which Sn promotes the nucleation of θ′, we investigated the structure and thickness of θ′ precipitates in a Al-1.7 at.% Cu alloy with trace additions of Sn (0.01 at.%). Scanning transmission electron microscopy imaging reveals that θ′ platelets recently nucleated at 160 and 200 °C exhibit a discrete distribution of specific, or "magic", thicknesses, corresponding to minima in the residual volumetric and shape misfit strain. This observation is unique to the Sn-assisted nucleation of θ′: θ′ platelets that undergo growth or form in the Sn-free alloy do not display this discrete distribution, although preference for the magic thicknesses persists. Direct evidence is presented that Sn does not accommodate volumetric misfit strain. Instead, it is shown that Sn in its solute form reduces either the interfacial energy of θ′ and/or the transformation shape strain associated with thicknesses intermediate to the magic thicknesses.

AB - θ′ is an effective strengthening precipitate phase in high-strength Al alloys; unfortunately its nucleation is difficult and usually requires assistance, such as that provided by Sn in Sn-microalloyed Al-Cu. In order to clarify the mechanisms by which Sn promotes the nucleation of θ′, we investigated the structure and thickness of θ′ precipitates in a Al-1.7 at.% Cu alloy with trace additions of Sn (0.01 at.%). Scanning transmission electron microscopy imaging reveals that θ′ platelets recently nucleated at 160 and 200 °C exhibit a discrete distribution of specific, or "magic", thicknesses, corresponding to minima in the residual volumetric and shape misfit strain. This observation is unique to the Sn-assisted nucleation of θ′: θ′ platelets that undergo growth or form in the Sn-free alloy do not display this discrete distribution, although preference for the magic thicknesses persists. Direct evidence is presented that Sn does not accommodate volumetric misfit strain. Instead, it is shown that Sn in its solute form reduces either the interfacial energy of θ′ and/or the transformation shape strain associated with thicknesses intermediate to the magic thicknesses.

KW - Aluminium alloys

KW - Heterogeneous nucleation

KW - High-angle annular dark field (HAADF)

KW - Precipitation

UR - http://www.scopus.com/inward/record.url?scp=81355161030&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=81355161030&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2011.10.015

DO - 10.1016/j.actamat.2011.10.015

M3 - Article

AN - SCOPUS:81355161030

VL - 60

SP - 633

EP - 644

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

IS - 2

ER -