The competition between metastable and equilibrium S (Al2CuMg) phase during the decomposition of Al-Cu-Mg alloys

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dc.contributor.authorStyles, MJen_AU
dc.contributor.authorMarceau, RKWen_AU
dc.contributor.authorBastow, TJen_AU
dc.contributor.authorBrand, HEAen_AU
dc.contributor.authorGibson, MAen_AU
dc.contributor.authorHutchinson, CRen_AU
dc.date.accessioned2021-12-08T20:37:58Zen_AU
dc.date.available2021-12-08T20:37:58Zen_AU
dc.date.issued2015-10-01en_AU
dc.date.statistics2021-11-12en_AU
dc.description.abstractThe decomposition sequence of the supersaturated solid solution leading to the formation of the equilibrium S (Al2CuMg) phase in Alsingle bondCusingle bondMg alloys has long been the subject of ambiguity and debate. Recent high-resolution synchrotron powder diffraction experiments have shown that the decomposition sequence does involve a metastable variant of the S phase (denoted S1), which has lattice parameters that are distinctly different to those of the equilibrium S phase (denoted S2). In this paper, the difference between these two phases is resolved using high-resolution synchrotron and neutron powder diffraction and atom probe tomography, and the transformation from S1 to S2 is characterised in detail by in situ synchrotron powder diffraction. The results of these experiments confirm that there are no significant differences between the crystal structures of S1 and S2, however, the powder diffraction and atom probe measurements both indicate that the S1 phase forms with a slight deficiency in Cu. The in situ isothermal aging experiments show that S1 forms rapidly, reaching its maximum concentration in only a few minutes at high temperatures, while complete conversion to the S2 phase can take thousands of hours at low temperature. The kinetics of S phase precipitation have been quantitatively analysed for the first time and it is shown that S1 phase forms with an average activation energy of 75 kJ/mol, which is much lower than the activation energy for Cu and Mg diffusion in an Al matrix (136 kJ/mol and 131 kJ/mol, respectively). The mechanism of the replacement of S1 with the equilibrium S2 phase is discussed. © Crown Copyright 2015 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.en_AU
dc.description.sponsorshipThis research was undertaken on the Powder Diffraction beamline at the Australian Synchrotron, Victoria, Australia (Experiments 5321 and 7230). Experiments at the ISIS Pulsed Neutron and Muon Source were supported by a beamtime allocation from the Science and Technology Facilities Council (Experiment RB1320197). The authors wish to thank beamline scientist Dr Aziz Daoud-Aladine for his assistance in setting up the HRPD instrument at ISIS, and Dr Santiago Corujeira Gallo for assistance with the in situ synchrotron data collection. Atom probe tomography measurements were carried out with the support of the Deakin University Advanced Characterisation Facility. MJS and MAG acknowledge the support of CSIRO through the Office of the Chief Executive (OCE) Science Program. TJB gratefully acknowledges the support of CSIRO’s OCE Science Leader program and the Advanced Materials transformational capability platform for this work.en_AU
dc.identifier.citationStyles, M. J., Marceau, R. K. W., Bastow, T. J., Brand, H. E. A., Gibson, M. A., & Hutchinson, C. R. (2015). The competition between metastable and equilibrium S (Al2CuMg) phase during the decomposition of Al-Cu-Mg alloys. Acta Materialia, 98, 64-80. doi:10.1016/j.actamat.2015.07.011en_AU
dc.identifier.issn1359-6454en_AU
dc.identifier.journaltitleActa Materialiaen_AU
dc.identifier.pagination64-80en_AU
dc.identifier.urihttps://doi.org/10.1016/j.actamat.2015.07.011en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/12393en_AU
dc.identifier.volume98en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectPrecipitationen_AU
dc.subjectX-ray diffractionen_AU
dc.subjectTomographyen_AU
dc.subjectAluminium alloysen_AU
dc.subjectAlloysen_AU
dc.subjectSynchrotronsen_AU
dc.titleThe competition between metastable and equilibrium S (Al2CuMg) phase during the decomposition of Al-Cu-Mg alloysen_AU
dc.typeJournal Articleen_AU
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