Aging behavior and strengthening mechanisms of coarsening resistant metastable θ' precipitates in an Al–Cu alloy

Sumit Bahl; Lianghua Xiong; Lawrence F. Allard; Richard A. Michi; Jonathan D. Poplawsky; Andrew Chihpin Chuang; Dileep Singh; Thomas R. Watkins; Dongwon Shin; J. Allen Haynes; Amit Shyam

doi:10.1016/j.matdes.2020.109378

Aging behavior and strengthening mechanisms of coarsening resistant metastable θ' precipitates in an Al–Cu alloy

Sumit Bahl, Lianghua Xiong, Lawrence F. Allard, Richard A. Michi, Jonathan D. Poplawsky, Andrew Chihpin Chuang, Dileep Singh, Thomas R. Watkins, Dongwon Shin, J. Allen Haynes, Amit Shyam

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86 Scopus citations

Abstract

An Al–Cu alloy micro-alloyed with Mn and Zr (ACMZ) was examined to understand the thermal stability and strengthening mechanism of metastable θ'-Al₂Cu precipitates with interfacial segregation after prolonged thermal exposure. The microstructure was characterized at multiple scales with techniques including synchrotron x-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy, and atom probe tomography. The θ' precipitates did not exhibit measurable coarsening after thermal exposure at 300°C for 5000 h. Kinetic effects of Mn and Zr interfacial segregation, which dominate over thermodynamic effects under these conditions, were necessary to understand the complete inhibition of precipitate coarsening. The θ' phase fraction was stable during the 5000 h exposure. This stable phase fraction was regarded as the metastable equilibrium value and was smaller than that predicted by the θ' solvus line of the ACMZ alloy. As expected from the observed phase stability, the alloy hardness also remained stable during the 5000 h exposure. An Orowan mechanism alone was inadequate to explain θ' precipitate strengthening. Additional strengthening mechanisms by θ' precipitates specifically related to the transformation strain may explain the observed hardness values.

Original language	English
Article number	109378
Journal	Materials and Design
Volume	198
DOIs	https://doi.org/10.1016/j.matdes.2020.109378
State	Published - Jan 15 2021

Funding

The research was sponsored by the Powertrain Materials Core Program, under the Propulsion Materials Program (managed by Jerry Gibbs), Vehicle Technologies Office, US Department of Energy (DOE). APT was conducted at ORNL's Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. Synchrotron x-ray measurements were performed at Advanced Photon Source, a US DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The authors thank Dana McClurg, Tom Geer, and James Burns for their technical assistance.

Funders	Funder number
Jerry Gibbs
US Department of Energy
U.S. Department of Energy
Office of Science
Argonne National Laboratory	DE-AC02-06CH11357

Keywords

Aging
Al–Cu alloys
Coarsening
Interfacial segregation
Strengthening mechanisms
θ'-AlCu

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10.1016/j.matdes.2020.109378

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title = "Aging behavior and strengthening mechanisms of coarsening resistant metastable θ' precipitates in an Al–Cu alloy",

abstract = "An Al–Cu alloy micro-alloyed with Mn and Zr (ACMZ) was examined to understand the thermal stability and strengthening mechanism of metastable θ'-Al2Cu precipitates with interfacial segregation after prolonged thermal exposure. The microstructure was characterized at multiple scales with techniques including synchrotron x-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy, and atom probe tomography. The θ' precipitates did not exhibit measurable coarsening after thermal exposure at 300°C for 5000 h. Kinetic effects of Mn and Zr interfacial segregation, which dominate over thermodynamic effects under these conditions, were necessary to understand the complete inhibition of precipitate coarsening. The θ' phase fraction was stable during the 5000 h exposure. This stable phase fraction was regarded as the metastable equilibrium value and was smaller than that predicted by the θ' solvus line of the ACMZ alloy. As expected from the observed phase stability, the alloy hardness also remained stable during the 5000 h exposure. An Orowan mechanism alone was inadequate to explain θ' precipitate strengthening. Additional strengthening mechanisms by θ' precipitates specifically related to the transformation strain may explain the observed hardness values.",

keywords = "Aging, Al–Cu alloys, Coarsening, Interfacial segregation, Strengthening mechanisms, θ'-AlCu",

author = "Sumit Bahl and Lianghua Xiong and Allard, {Lawrence F.} and Michi, {Richard A.} and Poplawsky, {Jonathan D.} and Chuang, {Andrew Chihpin} and Dileep Singh and Watkins, {Thomas R.} and Dongwon Shin and Haynes, {J. Allen} and Amit Shyam",

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year = "2021",

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doi = "10.1016/j.matdes.2020.109378",

language = "English",

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T1 - Aging behavior and strengthening mechanisms of coarsening resistant metastable θ' precipitates in an Al–Cu alloy

AU - Bahl, Sumit

AU - Xiong, Lianghua

AU - Allard, Lawrence F.

AU - Michi, Richard A.

AU - Poplawsky, Jonathan D.

AU - Chuang, Andrew Chihpin

AU - Singh, Dileep

AU - Watkins, Thomas R.

AU - Shin, Dongwon

AU - Haynes, J. Allen

AU - Shyam, Amit

PY - 2021/1/15

Y1 - 2021/1/15

N2 - An Al–Cu alloy micro-alloyed with Mn and Zr (ACMZ) was examined to understand the thermal stability and strengthening mechanism of metastable θ'-Al2Cu precipitates with interfacial segregation after prolonged thermal exposure. The microstructure was characterized at multiple scales with techniques including synchrotron x-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy, and atom probe tomography. The θ' precipitates did not exhibit measurable coarsening after thermal exposure at 300°C for 5000 h. Kinetic effects of Mn and Zr interfacial segregation, which dominate over thermodynamic effects under these conditions, were necessary to understand the complete inhibition of precipitate coarsening. The θ' phase fraction was stable during the 5000 h exposure. This stable phase fraction was regarded as the metastable equilibrium value and was smaller than that predicted by the θ' solvus line of the ACMZ alloy. As expected from the observed phase stability, the alloy hardness also remained stable during the 5000 h exposure. An Orowan mechanism alone was inadequate to explain θ' precipitate strengthening. Additional strengthening mechanisms by θ' precipitates specifically related to the transformation strain may explain the observed hardness values.

AB - An Al–Cu alloy micro-alloyed with Mn and Zr (ACMZ) was examined to understand the thermal stability and strengthening mechanism of metastable θ'-Al2Cu precipitates with interfacial segregation after prolonged thermal exposure. The microstructure was characterized at multiple scales with techniques including synchrotron x-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy, and atom probe tomography. The θ' precipitates did not exhibit measurable coarsening after thermal exposure at 300°C for 5000 h. Kinetic effects of Mn and Zr interfacial segregation, which dominate over thermodynamic effects under these conditions, were necessary to understand the complete inhibition of precipitate coarsening. The θ' phase fraction was stable during the 5000 h exposure. This stable phase fraction was regarded as the metastable equilibrium value and was smaller than that predicted by the θ' solvus line of the ACMZ alloy. As expected from the observed phase stability, the alloy hardness also remained stable during the 5000 h exposure. An Orowan mechanism alone was inadequate to explain θ' precipitate strengthening. Additional strengthening mechanisms by θ' precipitates specifically related to the transformation strain may explain the observed hardness values.

KW - Aging

KW - Al–Cu alloys

KW - Coarsening

KW - Interfacial segregation

KW - Strengthening mechanisms

KW - θ'-AlCu

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JO - Materials and Design

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Aging behavior and strengthening mechanisms of coarsening resistant metastable θ' precipitates in an Al–Cu alloy

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