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Title: In situ structural characterization of ageing kinetics in aluminum alloy 2024 across angstrom-to-micrometer length scales

Abstract

The precipitate structure and precipitation kinetics in an Al-Cu-Mg alloy (AA2024) aged at 190 °C, 208 °C, and 226 °C have been studied using ex situ Transmission Electron Microscopy (TEM) and in situ synchrotron-based, combined ultra-small angle X-ray scattering, small angle X-ray scattering (SAXS), and wide angle X-ray scattering (WAXS) across a length scale from sub-Angstrom to several micrometers. TEM brings information concerning the nature, morphology, and size of the precipitates while SAXS and WAXS provide qualitative and quantitative information concerning the time-dependent size and volume fraction evolution of the precipitates at different stages of the precipitation sequence. Within the experimental time resolution, precipitation at these ageing temperatures involves dissolution of nanometer-sized small clusters and formation of the planar S phase precipitates. Using a three-parameter scattering model constructed on the basis of TEM results, we established the temperature-dependent kinetics for the cluster-dissolution and S-phase formation processes simultaneously. These two processes are shown to have different kinetic rates, with the cluster-dissolution rate approximately double the S-phase formation rate. We identified a dissolution activation energy at (149.5 ± 14.6) kJ mol-1, which translates to (1.55 ± 0.15) eV/atom, as well as an activation energy for the formation of S precipitates at (129.2more » ± 5.4) kJ mol-1, i.e. (1.33 ± 0.06) eV/atom. Importantly, the SAXS/WAXS results show the absence of an intermediate Guinier-Preston Bagaryatsky 2 (GPB2)/S" phase in the samples under the experimental ageing conditions. These results are further validated by precipitation simulations that are based on Langer-Schwartz theory and a Kampmann-Wagner numerical method.« less

Authors:
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Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science - Office of Basic Energy Sciences - Scientific User Facilities Division; National Science Foundation (NSF); National Institute of Standards and Technology (NIST)
OSTI Identifier:
1267163
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Materialia; Journal Volume: 111
Country of Publication:
United States
Language:
English
Subject:
Al-Cu-Mg alloys; in situ; kinetics; precipitates; small angle x-ray scattering

Citation Formats

Zhang, Fan, Levine, Lyle E., Allen, Andrew J., Campbell, Carelyn E., Creuziger, Adam A., Kazantseva, Nataliya, and Ilavsky, Jan. In situ structural characterization of ageing kinetics in aluminum alloy 2024 across angstrom-to-micrometer length scales. United States: N. p., 2016. Web. doi:10.1016/j.actamat.2016.03.058.
Zhang, Fan, Levine, Lyle E., Allen, Andrew J., Campbell, Carelyn E., Creuziger, Adam A., Kazantseva, Nataliya, & Ilavsky, Jan. In situ structural characterization of ageing kinetics in aluminum alloy 2024 across angstrom-to-micrometer length scales. United States. doi:10.1016/j.actamat.2016.03.058.
Zhang, Fan, Levine, Lyle E., Allen, Andrew J., Campbell, Carelyn E., Creuziger, Adam A., Kazantseva, Nataliya, and Ilavsky, Jan. Wed . "In situ structural characterization of ageing kinetics in aluminum alloy 2024 across angstrom-to-micrometer length scales". United States. doi:10.1016/j.actamat.2016.03.058.
@article{osti_1267163,
title = {In situ structural characterization of ageing kinetics in aluminum alloy 2024 across angstrom-to-micrometer length scales},
author = {Zhang, Fan and Levine, Lyle E. and Allen, Andrew J. and Campbell, Carelyn E. and Creuziger, Adam A. and Kazantseva, Nataliya and Ilavsky, Jan},
abstractNote = {The precipitate structure and precipitation kinetics in an Al-Cu-Mg alloy (AA2024) aged at 190 °C, 208 °C, and 226 °C have been studied using ex situ Transmission Electron Microscopy (TEM) and in situ synchrotron-based, combined ultra-small angle X-ray scattering, small angle X-ray scattering (SAXS), and wide angle X-ray scattering (WAXS) across a length scale from sub-Angstrom to several micrometers. TEM brings information concerning the nature, morphology, and size of the precipitates while SAXS and WAXS provide qualitative and quantitative information concerning the time-dependent size and volume fraction evolution of the precipitates at different stages of the precipitation sequence. Within the experimental time resolution, precipitation at these ageing temperatures involves dissolution of nanometer-sized small clusters and formation of the planar S phase precipitates. Using a three-parameter scattering model constructed on the basis of TEM results, we established the temperature-dependent kinetics for the cluster-dissolution and S-phase formation processes simultaneously. These two processes are shown to have different kinetic rates, with the cluster-dissolution rate approximately double the S-phase formation rate. We identified a dissolution activation energy at (149.5 ± 14.6) kJ mol-1, which translates to (1.55 ± 0.15) eV/atom, as well as an activation energy for the formation of S precipitates at (129.2 ± 5.4) kJ mol-1, i.e. (1.33 ± 0.06) eV/atom. Importantly, the SAXS/WAXS results show the absence of an intermediate Guinier-Preston Bagaryatsky 2 (GPB2)/S" phase in the samples under the experimental ageing conditions. These results are further validated by precipitation simulations that are based on Langer-Schwartz theory and a Kampmann-Wagner numerical method.},
doi = {10.1016/j.actamat.2016.03.058},
journal = {Acta Materialia},
number = ,
volume = 111,
place = {United States},
year = {Wed Jun 01 00:00:00 EDT 2016},
month = {Wed Jun 01 00:00:00 EDT 2016}
}