Study of formation and reversion of Guinier-Preston zones in Al-4.5 at%Zn-x at%Mg alloys by positrons

Dlubek, G.; Krause, R.; Brümmer, O.; Plazaola, F.

doi:10.1007/bf01117364

Cited by 48 publications

(28 citation statements)

References 12 publications

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“…The same observation has been made for G.P. zones in Al-Zn alloys [25,26] while in Al-Zn-Mg [27] and Al-Cu [32] the appearance of vacancies associated with G.P. zones was concluded.…”

Section: Formation Of Cp Zones and Y'-precipitates During Isochrosupporting

confidence: 77%

A positron study of guinier-preston zones and γ′-precipitates in an AlAg alloy

Dlubek

Wendrock

Pawelzyk

1993

Phys. Stat. Sol. (a)

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Positron lifetime τ and momentum distribution (curve shape parameter S) measurements are performed to study the decomposition in an Al5.9 at% Ag alloy during isochronal and isothermal heat treatment of water‐quenched samples. The positron studies are supplemented by small‐angle X‐ray scattering experiments. It is proved that positrons become trapped by G.P. zones being free of any vacancy‐type or dislocation‐type defect and by semicoherent γ′‐precipitates. Positron trapping rates show the coarsening of G.P. zones simultaneously with the formation and growth of γ′ during isothermal aging above 170 °C. From the temperature dependence of τ and S the transformation of η‐zones into τ‐zones is concluded. The Ag content of zones changes from about 60 at% at 120 °C (η‐zones) to 35 at% at 190 °C (η‐zones) which is in good agreement with SAXS and AP‐FIM experiments. Evidence of a reversible change of the G.P. zone composition when alternating the temperature between 190 and 120 °C is found in both positron and SAXS experiments.

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“…The same observation has been made for G.P. zones in Al-Zn alloys [25,26] while in Al-Zn-Mg [27] and Al-Cu [32] the appearance of vacancies associated with G.P. zones was concluded.…”

Section: Formation Of Cp Zones and Y'-precipitates During Isochrosupporting

confidence: 77%

A positron study of guinier-preston zones and γ′-precipitates in an AlAg alloy

Dlubek

Wendrock

Pawelzyk

1993

Phys. Stat. Sol. (a)

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“…As reported, Mg plays a key role in the formation of GP zones [1,37] and Zn/Mg ratio has been suggested as the limiting factor in the formation of the Șƍ and Ș phases [1]. Being in the tensile stress field, the vacancy-solute atom complexes [22] formed after quenching will segregate at the dislocations or grain boundaries, that leads to the variance in the migration rates of the solute atoms.…”

Section: Effects Of Stress Aging Process On the Aging Precipitatementioning

confidence: 98%

Evolution of precipitate microstructure during stress aging of an Al–Zn–Mg–Cu alloy

Guo

Wang

et al. 2015

Materials Science and Engineering: A

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“…Thin plates on {111} planes have also been identified in Al-6.0Zn-2.0 Mg-1.0Cu (wt%) (AA7012) samples aged for short times using HRTEM [63] and in an Al-11.8Zn-1.5 Mg-1.7Cu-0.16Zr-0.12Fe-0.08Si alloys aged for 2 h at RT using HRTEM [64]. Plates on {111} planes are also confirmed by first principle calculations to be energetically favourable [65,66].…”

Section: The Reactions During the Quenchmentioning

confidence: 99%

Predicting the quench sensitivity of Al–Zn–Mg–Cu alloys: A model for linear cooling and strengthening

et al. 2015

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In this work the quench sensitivity of Al-Zn-Mg-Cu alloys is studied through continuous cooling at constant rates of a range of alloys using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and hardness testing. The DSC, TEM and SEM data show that the cooling reactions are dominated by a high temperature reaction (typically ~450 °C down to ~350 °C) due mostly to S-Al2CuMg phase formation, a medium temperature reaction (~350 °C down to ~250 °C) due predominantly to -Mg(Al,Cu,Zn)2 phase formation and a lower temperature reaction (~250 °C down to ~150 °C) due to a Zn-Cu rich thin plate phase. A new, physically-based model is constructed to predict rates of all reactions, enthalpy changes and resulting yield strength in the artificially aged condition. The model incorporates a recently derived model for diffusion-controlled reactions based on the extended volume fraction concept as well as recent findings from first principles modelling of enthalpies of the relevant phases. The model shows a near perfect correspondence with data on all 6 alloys studied extensively by cooling DSC and hardness testing, and 2 allows prediction of the influence of the 3 major elements and 3 dispersoid forming elements on quench sensitivity. Graphical abstract Highlights

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Study of formation and reversion of Guinier-Preston zones in Al-4.5 at%Zn-x at%Mg alloys by positrons

Cited by 48 publications

References 12 publications

A positron study of guinier-preston zones and γ′-precipitates in an AlAg alloy

A positron study of guinier-preston zones and γ′-precipitates in an AlAg alloy

Evolution of precipitate microstructure during stress aging of an Al–Zn–Mg–Cu alloy

Predicting the quench sensitivity of Al–Zn–Mg–Cu alloys: A model for linear cooling and strengthening

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