A comparative study of precipitate composition and volume fraction in an Al–Zn–Mg alloy using tomographic atom probe and small-angle X-ray scattering

Deschamps, A.; Bigot, A.; Livet, F.; Auger, Pierre; Bréchet, Y.; Blavette, D.

doi:10.1080/01418610108217154

Cited by 68 publications

(35 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, we will approximate the precipitation by assuming that the precipitation in the grain is exclusively η′ phase. Some controversy exists concerning the composition of the η′ phase, with atom-probe data suggesting a Zn:Mg ratio of about 1.2-1.5 with very low Cu content (Cu:Zn=0.1) [42,43,44], and small angle X-ray scattering (SAXS) a suggesting a much higher Zn content [44], closer to the Zn:Mg ratio of 2.5 in the suggested structure of η′ phase based on an analysis of selected area diffraction data [45]. We will assume that the Zn:Mg ratio can be approximated to equal 2, and that in good approximation η′ does not contain Cu.…”

Section: Precipitation and Coarseningmentioning

confidence: 99%

A model for the electrical conductivity of peak-aged and overaged Al-Zn-Mg-Cu alloys

Starink

2003

Metall Mater Trans A

113

View full text Add to dashboard Cite

A physically-based model for the electrical conductivity of peak aged and overaged Al-Zn-Mg-Cu (7xxx series) alloys is presented. The model includes calculations of the η and the S phase solvus (using a regular solution model), taking account of the capillary effect and η coarsening. It takes account of the conductivity of grains (incorporating dissolved alloying elements, undissolved particles and precipitates) and solute depleted areas at the grain boundaries. Data from optical microscopy, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) along with energy dispersive X-ray spectrometry (EDS), and transmission electron microscopy (TEM) are consistent with the model and its predictions. The model has been successfully used to fit and predict the conductivity data of a set of 7xxx alloys including both Zr containing alloys and Cr containing alloys under various ageing conditions, achieving an accuracy of about 1% in predicting unseen conductivity data from this set of alloys.

show abstract

Section: Precipitation and Coarseningmentioning

confidence: 99%

A model for the electrical conductivity of peak-aged and overaged Al-Zn-Mg-Cu alloys

Starink

2003

Metall Mater Trans A

113

View full text Add to dashboard Cite

show abstract

“…when all alloying elements would precipitate. In calculating f max for the Al-Zn-Mg-Cu alloys we take account of Al in the precipitate by taking the Al fraction m/(a+b+c) equal to the one experimentally determined from APFIM for an Al-6.1Zn-2.35Mg-0.1Zr alloy aged 10h at 160°C: m/(a+b+c)=0.29 [34]. As the atomic density of η is equal to that of FCC Al, the atomic fraction of precipitate is equal to the volume fraction [34].…”

Section: The (Semi-) Equilibrium Statementioning

confidence: 99%

A model for the yield strength of overaged Al–Zn–Mg–Cu alloys

2003

View full text Add to dashboard Cite

A model for the yield strength of multi-component alloys is presented and applied to overaged Al-Zn-Mg-Cu alloys (7xxx series). The model is based on an approximation of the strengthening due to precipitate by-passing during precipitate coarsening and takes account of ternary and higher order systems. It takes account of the influence of supersaturation on precipitation rates and of volume fraction on coarsening rates, as well crystallographic texture and recrystallisation. The model has been successfully used to fit and predict the yield strength data of 21 Al-Zn-Mg-Cu alloys, with compositions spread over the whole range of commercial alloying compositions, and which were aged for a range of times and temperatures to produce yield strengths ranging from 400 to 600 MPa. All but one of the microstructural and reaction rate parameters in the model are determined on the basis of microstructural data, with one parameter fitted to yield strength data.The resulting accuracy in predicting unseen proof strength data is 14 MPa. In support of the model, microstructures and phase transformations of 7xxx alloys were studied by a range of techniques, including differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD) in an SEM with a field emission gun (FEG-SEM). Published as: Acta Mater., 2003, Vol. 51, pp. 5131-5150 IntroductionSince the 1940s significant progress has been made in quantitatively predicting the individual strengthening effects in simple metallic alloy systems, such as solution strengthening, strengthening due to coherent particles, dispersion strengthening, grain boundary strengthening, etc. In complex heat treatable commercial alloys, a superposition of a multitude of strengthening effects occurs, and the prediction of the yield strength as a function of composition, thermo-mechanical processing, and heat treatment attracts great interests, both from commercial and academic perspective. Recent published literature on modelling of the yield strength of Al based alloys [1,2,3,4,5,6,7] Published as : Acta Mater., 2003, Vol. 51, pp. 5131-5150 Most commercial 7xxx alloys can be categorized in two groups depending on the type of grain structure controlling element that is added. Zr containing alloys will contain β′ phase (Al 3 Zr, L1 2 structure) particles, whilst Cr containing alloys will generally contain Al 7 Cr particles. In aluminium metallurgy, these grain structure controlling particles are generally called dispersoids.The type of dispersoids will influence the recrystallisation and quench sensitivity of the alloy.Through varying recrystallisation, the dispersoids also influence the texture and the related anisotropy.In the present paper we will present a model that is designed for modelling and predicting strength in overaged multi-component alloys, in which the composition of the precipitates is variable, and closely related to the alloy composition. The model is mostly based on physical principles, but to accommodate the complexities introduced by the multi-com...

show abstract

“…In the past decade, much research effort has been put into evaluating the composition of nanoscale precipitates in Al alloys due to the development of advanced characterization tools such as atom probe tomography (APT). 2,[5][6][7] Sha and Cerezo studied the chemistry evolution of the early-stage precipitates in 7050 Al alloy using transmission electron microscopy (TEM) and APT. 2 Marlaud and Deschamps investigated the composition of precipitates and the solid solution in Al-Zn-Mg-Cu alloys in peak-aged and over-aged conditions by combining APT and systematic anomalous small-angle X-ray scattering (ASAXS) techniques.…”

mentioning

confidence: 99%

Mechanism of Localized Breakdown of 7000 Series Aluminum Alloys

Wang

Frankel

Jiang

et al. 2013

J. Electrochem. Soc.

View full text Add to dashboard Cite

The localized breakdown behavior of AA7055 alloy, and an Al-Zn-Mg alloy having no Cu, with different tempers was studied in 3.5 wt% NaCl solution by an in situ observation system during polarization. Three potentials at which the current increased rapidly were found for AA7055-T6 (peak-aged) samples. The first breakdown potential corresponded to the transient dissolution of an active surface layer formed during surface preparation by abrading with grinding paper. The second potential at which the current increased rapidly was associated with crevice corrosion and was not a true breakdown potential. The second breakdown potential was associated with pitting of the underlying bulk alloy. However, no surface layer attack and a single breakdown potential were observed for AA7055-T73 (over-aged) samples and for the Cu-free Al-Zn-Mg samples in the peak-aged condition. All three samples contained surface layers consisting of nano-grains with the solute-rich bands formed by surface preparation. Both the Zn-rich bands in the surface layer and the Cu content in matrix solid solution of the underlying bulk alloy are responsible for surface layer attack. The change in pitting potential with over-aged tempers could be rationalized based on the Cu content in the matrix. Precipitation-hardenable aluminum alloys are main structural materials for aircrafts due to their high strength-to-density ratio. The AlZn-Mg(-Cu) alloys form precipitates following the general precipitation sequence of supersaturated solid solution, GP zones, metastable η , and stable η.1,2 Metastable η phase is believed to be the main hardening phase and responsible for the peak hardening in Al-ZnMg(-Cu) alloys.2 The equilibrium phase η has the hexagonal structure of MgZn 2 , but Al and Cu can substitute for Zn, and the stoichiometry of this phase can be described as Mg(Zn,Al,Cu) 2 in Cu containing 7××× series Al alloys.3,4 Aging treatments produce changes in the morphology, chemistry, size and density of precipitates and the composition of the solid solution. In the past decade, much research effort has been put into evaluating the composition of nanoscale precipitates in Al alloys due to the development of advanced characterization tools such as atom probe tomography (APT).2,5-7 Sha and Cerezo studied the chemistry evolution of the early-stage precipitates in 7050 Al alloy using transmission electron microscopy (TEM) and APT.2 Marlaud and Deschamps investigated the composition of precipitates and the solid solution in Al-Zn-Mg-Cu alloys in peak-aged and over-aged conditions by combining APT and systematic anomalous small-angle X-ray scattering (ASAXS) techniques.7 This microstructural information has also facilitated a better understanding of corrosion behavior in 7××× series Al alloys with different heat treatments.The localized breakdown behavior of 7××× series Al alloys has been studied extensively. 4,[8][9][10][11][12] The anodic polarization curve for 7×××-T6 Al alloys in NaCl solution exhibits two breakdown potentials. However, only one breakdown pot...

show abstract

A comparative study of precipitate composition and volume fraction in an Al–Zn–Mg alloy using tomographic atom probe and small-angle X-ray scattering

Cited by 68 publications

References 19 publications

A model for the electrical conductivity of peak-aged and overaged Al-Zn-Mg-Cu alloys

A model for the electrical conductivity of peak-aged and overaged Al-Zn-Mg-Cu alloys

A model for the yield strength of overaged Al–Zn–Mg–Cu alloys

Mechanism of Localized Breakdown of 7000 Series Aluminum Alloys

Contact Info

Product

Resources

About