Atomic structures of interfacial solute gateways to θ′ precipitates in Al-Cu alloys

M. F. Chisholm; D. Shin; G. Duscher; M. P. Oxley; L. F. Allard; J. D. Poplawsky; A. Shyam

doi:10.1016/j.actamat.2021.116891

Atomic structures of interfacial solute gateways to θ′ precipitates in Al-Cu alloys

M. F. Chisholm, D. Shin, G. Duscher, M. P. Oxley, L. F. Allard, J. D. Poplawsky, A. Shyam

Research output: Contribution to journal › Article › peer-review

23 Scopus citations

Abstract

Many materials employed in critical structural applications depend upon metastable strengthening precipitates that transform or dissolve at elevated temperatures. Herein, aberration-corrected scanning transmission electron microscopy and first-principles calculations are used to accurately determine the atomic structure of the highly mobile, semi-coherent precipitate interfaces that control this process in the classic θ′ (Al₂Cu) precipitate in the Al-Cu system. Semi-coherent {110} interfaces are found to be composed of an array of unexpected misfit dislocations that are arranged in two different structural units. Dislocations accommodate nearly all of the misfit between the Al matrix and strengthening phase. Cu is observed to segregate to the compressed edge of the dislocation cores at specific sites in this interface. First-principles calculations revealed the energetic landscape that facilitates these sites to become entry and exit gateways of Cu atoms in this semi-coherent interface. This investigation reveals critical features within semi-coherent interfaces that determine the thermal stability of precipitation-hardened alloys.

Original language	English
Article number	116891
Journal	Acta Materialia
Volume	212
DOIs	https://doi.org/10.1016/j.actamat.2021.116891
State	Published - Jun 15 2021

Funding

Research sponsored by Powertrain Materials Core Program, under the Propulsion Materials Program, Vehicle Technologies Office, U.S. Department of Energy (MFC, DS, LFA, JDP, AS) and the U.S. DOE Basic Energy Sciences, Materials Sciences, and Engineering Division (GD, MPO, MFC). The authors appreciate the support provided by the Oak Ridge Leadership Computing Facility at ORNL. The APT used in the analysis of the data was conducted at ORNL's Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility (JDP). Research sponsored by Powertrain Materials Core Program, under the Propulsion Materials Program, Vehicle Technologies Office, U.S. Department of Energy (MFC, DS, LFA, JDP, AS) and the U.S. DOE Basic Energy Sciences, Materials Sciences, and Engineering Division (GD, MPO, MFC). The authors appreciate the support provided by the Oak Ridge Leadership Computing Facility at ORNL. The APT used in the analysis of the data was conducted at ORNL's Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility (JDP).

Funders	Funder number
MFC
Powertrain Materials Core Program
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Oak Ridge National Laboratory
Division of Materials Sciences and Engineering

Keywords

Al alloys
Atomic structure
Interfacial segregation
Precipitates
STEM

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10.1016/j.actamat.2021.116891

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title = "Atomic structures of interfacial solute gateways to θ′ precipitates in Al-Cu alloys",

abstract = "Many materials employed in critical structural applications depend upon metastable strengthening precipitates that transform or dissolve at elevated temperatures. Herein, aberration-corrected scanning transmission electron microscopy and first-principles calculations are used to accurately determine the atomic structure of the highly mobile, semi-coherent precipitate interfaces that control this process in the classic θ′ (Al2Cu) precipitate in the Al-Cu system. Semi-coherent {110} interfaces are found to be composed of an array of unexpected misfit dislocations that are arranged in two different structural units. Dislocations accommodate nearly all of the misfit between the Al matrix and strengthening phase. Cu is observed to segregate to the compressed edge of the dislocation cores at specific sites in this interface. First-principles calculations revealed the energetic landscape that facilitates these sites to become entry and exit gateways of Cu atoms in this semi-coherent interface. This investigation reveals critical features within semi-coherent interfaces that determine the thermal stability of precipitation-hardened alloys.",

keywords = "Al alloys, Atomic structure, Interfacial segregation, Precipitates, STEM",

author = "Chisholm, {M. F.} and D. Shin and G. Duscher and Oxley, {M. P.} and Allard, {L. F.} and Poplawsky, {J. D.} and A. Shyam",

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AU - Chisholm, M. F.

AU - Shin, D.

AU - Duscher, G.

AU - Oxley, M. P.

AU - Allard, L. F.

AU - Poplawsky, J. D.

AU - Shyam, A.

PY - 2021/6/15

Y1 - 2021/6/15

N2 - Many materials employed in critical structural applications depend upon metastable strengthening precipitates that transform or dissolve at elevated temperatures. Herein, aberration-corrected scanning transmission electron microscopy and first-principles calculations are used to accurately determine the atomic structure of the highly mobile, semi-coherent precipitate interfaces that control this process in the classic θ′ (Al2Cu) precipitate in the Al-Cu system. Semi-coherent {110} interfaces are found to be composed of an array of unexpected misfit dislocations that are arranged in two different structural units. Dislocations accommodate nearly all of the misfit between the Al matrix and strengthening phase. Cu is observed to segregate to the compressed edge of the dislocation cores at specific sites in this interface. First-principles calculations revealed the energetic landscape that facilitates these sites to become entry and exit gateways of Cu atoms in this semi-coherent interface. This investigation reveals critical features within semi-coherent interfaces that determine the thermal stability of precipitation-hardened alloys.

AB - Many materials employed in critical structural applications depend upon metastable strengthening precipitates that transform or dissolve at elevated temperatures. Herein, aberration-corrected scanning transmission electron microscopy and first-principles calculations are used to accurately determine the atomic structure of the highly mobile, semi-coherent precipitate interfaces that control this process in the classic θ′ (Al2Cu) precipitate in the Al-Cu system. Semi-coherent {110} interfaces are found to be composed of an array of unexpected misfit dislocations that are arranged in two different structural units. Dislocations accommodate nearly all of the misfit between the Al matrix and strengthening phase. Cu is observed to segregate to the compressed edge of the dislocation cores at specific sites in this interface. First-principles calculations revealed the energetic landscape that facilitates these sites to become entry and exit gateways of Cu atoms in this semi-coherent interface. This investigation reveals critical features within semi-coherent interfaces that determine the thermal stability of precipitation-hardened alloys.

KW - Al alloys

KW - Atomic structure

KW - Interfacial segregation

KW - Precipitates

KW - STEM

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JO - Acta Materialia

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ER -

Atomic structures of interfacial solute gateways to θ′ precipitates in Al-Cu alloys

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