The bulk and interfacial structures of the η (Al2Au) precipitate phase

Laure Bourgeois, Zezhong Zhang, Jiehua Li, Nikhil V. Medhekar

Research output: Contribution to journalArticleResearchpeer-review

3 Citations (Scopus)

Abstract

The atomic structure of the Al2Au η precipitate phase in an Al-0.2 at. %Au alloy is investigated using high-resolution scanning transmission electron microscopy together with first principles and elasticity theory calculations. We find experimentally that precipitates above a certain thickness exhibit the cubic crystal structure of the equilibrium phase η. However below that thickness precipitates adopt a tetragonal distortion of the cubic structure of η, which can be regarded as an intermediate η′ phase and allows full two-dimensional coherence for very thin precipitates (up to two unit cells' thick). Despite the structural similarities of the bulk structures of η and θ′ (Al2Cu) precipitate phases, the former displays interfacial structures that differ markedly from those recently observed in θ′. This can be attributed to the much lower defect energy in aluminium of solute Au compared with solute Cu. Both first-principles and elasticity theory calculations are in good agreement with our experimental observations.

Original languageEnglish
Pages (from-to)284-293
Number of pages10
JournalActa Materialia
Volume105
DOIs
Publication statusPublished - 2016

Keywords

  • Aluminium alloys
  • Atomic structure
  • Precipitation
  • Scanning transmission electron microscopy (STEM)

Cite this

@article{04ab95ecb48740a19c6524bd65b731b0,
title = "The bulk and interfacial structures of the η (Al2Au) precipitate phase",
abstract = "The atomic structure of the Al2Au η precipitate phase in an Al-0.2 at. {\%}Au alloy is investigated using high-resolution scanning transmission electron microscopy together with first principles and elasticity theory calculations. We find experimentally that precipitates above a certain thickness exhibit the cubic crystal structure of the equilibrium phase η. However below that thickness precipitates adopt a tetragonal distortion of the cubic structure of η, which can be regarded as an intermediate η′ phase and allows full two-dimensional coherence for very thin precipitates (up to two unit cells' thick). Despite the structural similarities of the bulk structures of η and θ′ (Al2Cu) precipitate phases, the former displays interfacial structures that differ markedly from those recently observed in θ′. This can be attributed to the much lower defect energy in aluminium of solute Au compared with solute Cu. Both first-principles and elasticity theory calculations are in good agreement with our experimental observations.",
keywords = "Aluminium alloys, Atomic structure, Precipitation, Scanning transmission electron microscopy (STEM)",
author = "Laure Bourgeois and Zezhong Zhang and Jiehua Li and Medhekar, {Nikhil V.}",
year = "2016",
doi = "10.1016/j.actamat.2015.12.035",
language = "English",
volume = "105",
pages = "284--293",
journal = "Acta Materialia",
issn = "1359-6454",
publisher = "Elsevier",

}

The bulk and interfacial structures of the η (Al2Au) precipitate phase. / Bourgeois, Laure; Zhang, Zezhong; Li, Jiehua; Medhekar, Nikhil V.

In: Acta Materialia, Vol. 105, 2016, p. 284-293.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - The bulk and interfacial structures of the η (Al2Au) precipitate phase

AU - Bourgeois, Laure

AU - Zhang, Zezhong

AU - Li, Jiehua

AU - Medhekar, Nikhil V.

PY - 2016

Y1 - 2016

N2 - The atomic structure of the Al2Au η precipitate phase in an Al-0.2 at. %Au alloy is investigated using high-resolution scanning transmission electron microscopy together with first principles and elasticity theory calculations. We find experimentally that precipitates above a certain thickness exhibit the cubic crystal structure of the equilibrium phase η. However below that thickness precipitates adopt a tetragonal distortion of the cubic structure of η, which can be regarded as an intermediate η′ phase and allows full two-dimensional coherence for very thin precipitates (up to two unit cells' thick). Despite the structural similarities of the bulk structures of η and θ′ (Al2Cu) precipitate phases, the former displays interfacial structures that differ markedly from those recently observed in θ′. This can be attributed to the much lower defect energy in aluminium of solute Au compared with solute Cu. Both first-principles and elasticity theory calculations are in good agreement with our experimental observations.

AB - The atomic structure of the Al2Au η precipitate phase in an Al-0.2 at. %Au alloy is investigated using high-resolution scanning transmission electron microscopy together with first principles and elasticity theory calculations. We find experimentally that precipitates above a certain thickness exhibit the cubic crystal structure of the equilibrium phase η. However below that thickness precipitates adopt a tetragonal distortion of the cubic structure of η, which can be regarded as an intermediate η′ phase and allows full two-dimensional coherence for very thin precipitates (up to two unit cells' thick). Despite the structural similarities of the bulk structures of η and θ′ (Al2Cu) precipitate phases, the former displays interfacial structures that differ markedly from those recently observed in θ′. This can be attributed to the much lower defect energy in aluminium of solute Au compared with solute Cu. Both first-principles and elasticity theory calculations are in good agreement with our experimental observations.

KW - Aluminium alloys

KW - Atomic structure

KW - Precipitation

KW - Scanning transmission electron microscopy (STEM)

UR - http://www.scopus.com/inward/record.url?scp=84953791142&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2015.12.035

DO - 10.1016/j.actamat.2015.12.035

M3 - Article

VL - 105

SP - 284

EP - 293

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

ER -