Composition of β″ precipitates in Al–Mg–Si alloys by atom probe tomography and first principles calculations

Hasting, H. S.; Frøseth, A. G.; Andersen, Sigmund Jarle; Vissers, R.; Walmsley, John C.; Marioara, Calin Daniel; Danoix, F.; Lefebvre, W.; Holmestad, Randi

doi:10.1063/1.3269714

Cited by 201 publications

(136 citation statements)

References 37 publications

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“…The model of the S phase is consistent with the Perlitz-Westgren model with composition Al 2 MgCu and space group (Perlitz and Westgren, 1943). The β'' phase matches well with the model of Hasting et al, having composition Al 2 Mg 5 Si 4 and space group 2/ (Hasting et al, 2009). The results were consistent between EELS and EDS, although atomic columns were not visible in the Si-K EELS map.…”

Section: Chemistry In the Mapped Precipitatessupporting

confidence: 84%

“…Other structures are still disputed after aberration-corrected ADF imaging due to a content of elements with similar atomic numbers: The β'' phase in Al-Mg-Si alloys was first well established as Mg 5 Si 6 (Zandbergen et al, 1997;Chen et al, 2006), then proposed as both Al 2 Mg 5 Si 4 (Hasting et al, 2009) and Al 3 Mg 4 Si 4 (Ninive et al, 2014). The Q' phase in Al-Mg-Si-Cu alloys has been suggested as Al 3 Mg 9 Si 7 Cu 2 on the basis of density functional theory calculations (Wolverton, 2001), with no decisive experimental evidence.…”

Section: Introductionmentioning

confidence: 99%

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Atomic-resolution chemical mapping of ordered precipitates in Al alloys using energy-dispersive X-ray spectroscopy

Wenner

Jones

Marioara

et al. 2017

Micron

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Scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDS) is a common technique for chemical mapping in thin samples. Obtaining high-resolution elemental maps in the STEM is jointly dependent on stepping the sharply focused electron probe in a precise raster, on collecting a significant number of characteristic X-rays over time, and on avoiding damage to the sample. In this work, 80 kV aberration-corrected STEM-EDS mapping was performed on ordered precipitates in aluminium alloys. Probe and sample instability problems are handled by acquiring series of annular dark-field (ADF) images and simultaneous EDS volumes, which are aligned and non-rigidly registered after acquisition. The summed EDS volumes yield elemental maps of Al, Mg, Si, and Cu, with sufficient resolution and signal-to-noise ratio to determine the elemental species of each atomic column in a periodic structure, and in some cases the species of single atomic columns. Within the uncertainty of the technique, S and β'' phases were found to have pure elemental atomic columns with compositions Al 2 CuMg and Al 2 Mg 5 Si 4 , respectively. The Q' phase showed some variation in chemistry across a single precipitate, although the majority of unit cells had a composition Al 6 Mg 6 Si 7.2 Cu 2 .

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Section: Chemistry In the Mapped Precipitatessupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Atomic-resolution chemical mapping of ordered precipitates in Al alloys using energy-dispersive X-ray spectroscopy

Wenner

Jones

Marioara

et al. 2017

Micron

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“…This is largely due to the poor statistics of only few precipitates detected in previous atom probe measurements. Recent first-principle calculations suggest that the lowest formation enthalpy configuration of β″ has a Mg:Si ratio of 1.25 [35], which is consistent with 1.2 detected among the large β″ precipitates in the alloy.…”

Section: The Partitioning Of Solutes During Precipitation Of the Allosupporting

confidence: 63%

Solute nanostructures and their strengthening effects in Al–7Si–0.6Mg alloy F357

et al. 2012

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The solute-nanostructures formed in the primary α-Al grains of a Semi-Solid Metal cast Al-7Si-0.6Mg alloy (F357) during ageing at 180°C, and the age-hardening response of the alloy have been systematically investigated using transmission electron microscopy, atom probe tomography and hardness testing. A 120-h natural pre-ageing led to the formation of solute clusters and GP zones. The natural pre-ageing slowed down the precipitation kinetics six-fold during 1 h ageing at 180°C, but this effect diminished after 4 h when the sample reached the same hardness as that without the pre-ageing treatment. It reduced the number density of β″-needles to approximately half of that formed in samples without the treatment, and postponed the peak hardness occurrence to 4 h, 4 times that of the as-quenched sample. A hardness plateau developed in the as-quenched sample between 1 h and 4 h ageing corresponds to the growth of 2 the β″ precipitates and a significant concurrent decrease of solute clusters and GP zones. The average Mg:Si ratio of early solute clusters is < 0.7 while that of GP zones changes from 0.8 to 0.9 with increasing in their size, and that of β″-needles increases from 0.9 to 1.2. β″-needles, GP zones and solute clusters are important strengthening solute nanostructures of the alloy. The partitioning of solutes and precipitation kinetics of the alloy are discussed in detail.

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“…The precipitate needles obstruct dislocations, consequently increasing the material strength. The needles in 6xxx alloys mainly consist of Mg and Si in addition to Al itself [1] [2] [3], but other added elements may enter the precipitates as well. Elements like Li, Cu, Zn, Ag and Ge have proven to be beneficial for the nucleation and growth of precipitates, and they have consequently been added in multiple combinations and amounts [4] [5] [6] [7] [8].…”

Section: Introductionmentioning

confidence: 99%

Atomistic details of precipitates in lean Al–Mg–Si alloys with trace additions of Ag and Ge studied by HAADF-STEM and DFT

Mørtsell

Andersen

Friis

et al. 2017

Philosophical Magazine

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Bonding energies and volume misfits for alloying elements and vacancies in multicomponent Al-Mg-Si alloys have been calculated using density functional theory and the results have been compared with numbers obtained by atomic scale precipitate structure analysis, using high angle annular dark-field scanning transmission electron microscopy. The techniques in combination provide new insight into precipitation in these alloys. In the Ge containing alloy were found two new stacking configurations of the well-known strengthening phase β". In the alloy with Ag a new Q'/C -like local configuration containing Ag was discovered, and a model has been proposed. The experimental results are justified by simulations.

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Composition of β″ precipitates in Al–Mg–Si alloys by atom probe tomography and first principles calculations

Cited by 201 publications

References 37 publications

Atomic-resolution chemical mapping of ordered precipitates in Al alloys using energy-dispersive X-ray spectroscopy

Atomic-resolution chemical mapping of ordered precipitates in Al alloys using energy-dispersive X-ray spectroscopy

Solute nanostructures and their strengthening effects in Al–7Si–0.6Mg alloy F357

Atomistic details of precipitates in lean Al–Mg–Si alloys with trace additions of Ag and Ge studied by HAADF-STEM and DFT

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