Determination of kinetic parameters from calorimetric study of solid state reactions in 7150 Al-Zn-Mg alloy

Ghosh, K. S.; Gao, Nong

doi:10.1016/s1003-6326(11)60843-1

Cited by 65 publications

(67 citation statements)

References 32 publications

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“…We decided to obtain the activation energy for the diffusion process that governs formation of the  phase (i.e. the MTR) in a AA7150 alloy from the DSC data for the exothermic reaction in the corresponding temperature range in [79]. To this end the Type B-1.92 method for activation energy analysis [80] was applied on peak temperatures reported in [79], which produced ED(MTR) = 60 kJ/mol (using only heating rates at which the reaction is clearly visible).…”

Section: Thermal Activation Of the Reactions And Their Activation Enementioning

confidence: 99%

“…the MTR) in a AA7150 alloy from the DSC data for the exothermic reaction in the corresponding temperature range in [79]. To this end the Type B-1.92 method for activation energy analysis [80] was applied on peak temperatures reported in [79], which produced ED(MTR) = 60 kJ/mol (using only heating rates at which the reaction is clearly visible). It is well known that at the low temperatures at which the LTR occurs, diffusion rates of alloying elements such as Zn in the presence of an equilibrium concentration of vacancies are much too low to allow any significant diffusion.…”

Section: Thermal Activation Of the Reactions And Their Activation Enementioning

confidence: 99%

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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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Section: Thermal Activation Of the Reactions And Their Activation Enementioning

confidence: 99%

Section: Thermal Activation Of the Reactions And Their Activation Enementioning

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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“…Addition of Zn into these alloys improves castability, mechanical properties and helps to overcome hot tearing [1][2][3][4]. However, the addition of Zn element deteriorates the atmospheric corrosion resistance of the 7000 series Al alloys and so this limits the usage of these alloys [5].…”

Section: Introductionmentioning

confidence: 99%

The effect of Zn on the microarc oxidation coating behavior of synthetic Al–Zn binary alloys

Güleç

2012

Journal of Alloys and Compounds

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“…These peaks are results of h and h¢ precipitation from solid solution. [14][15][16] In the RRA curve, there exists only one peak related to h precipitation. This means that there are still a lot of elements in solid solution after T6 treatment suggesting that either time or temperature or both are not enough for diffusion and precipitation of the elements.…”

Section: Mechanical Strengthmentioning

confidence: 99%

Development of a heat treatment for increasing the mechanical properties and stress corrosion resistance of 7000 Al alloys

Shakouri¹,

Esmailian²,

Shabestari³

2017

Mater. Tehnol.

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A retrogression and re-ageing (RRA) treatment is a three-step heat treatment that can improve both the mechanical strength and the corrosion resistance in aluminum alloys. In this work, the mechanical and stress corrosion properties under various ageing treatment conditions were investigated in an Al-8.5Zn-2.1Mg-2Cu-0.2Ag (w/%) alloy. The treatments were the T6 conventional method followed by a retrogression and re-ageing (RRA) treatment. Tensile test, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and differential scanning calorimetry (DSC) were used to investigate the mechanical and stress corrosion cracking (SCC) properties. The results showed that both, the strength and the corrosion resistance criteria (SCR), which is defined as the ratio between the remaining strength percent in stressed and un-stressed conditions, improve after the RRA treatment. The tensile strength and SCR criteria for the T6 heat treatment were 547 MPa and 71 % initially and then increased to 612 MPa and 95 % for the RRA treatment, respectively. Moreover, the EDS results showed that in grain-boundary precipitates the Cu concentration is much higher for the RRA in comparison with the T6 treatment, but it is lower for the matrix precipitates in the RRA treatment. Keywords: aluminium alloys, stress corrosion resistance, precipitation, retrogression and re-ageing Obdelava z retrogresijo in ponovno o`ivitvijo (angl. RRA) je tristopenjska toplotna obdelava, s katero lahko izbolj{amo tako mehansko trdnost kot odpornosti proti koroziji pri aluminijevih zlitinah. V pri~ujo~em delu so bile raziskovane mehanske lastnosti in lastnosti odpornosti proti koroziji pri zlitini Al-8.5Zn-2.1Mg-2Cu-0.2Ag (w/%) pod razli~nimi pogoji obdelave staranja. Izvedeni so bili testi po konvencionalni T6 metodi, z upo{tevanjem RRA obdelave. Natezni preiskus, vrsti~na elektronska mikroskopija (SEM), energijsko disperzijska rentgenska spektroskopija (EDS) in DSC-testiranja so bili izvedeni, da bi raziskali mehanske in napetostno-korozijske lomne lastnosti (angl. SCC). Rezultati so pokazali, da se oba kriterija tako trdnost kot odpornost proti koroziji, ki definirata razmerje med procentom zaostale trdnosti pri napetostnih in nenapetostnih pogojih, po RRA-obdelavi izbolj{ata. Klju~ne besede: aluminijeve zlitine, odpornost proti koroziji, oborine, retrogresija in ponovno staranje

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Determination of kinetic parameters from calorimetric study of solid state reactions in 7150 Al-Zn-Mg alloy

Cited by 65 publications

References 32 publications

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

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

The effect of Zn on the microarc oxidation coating behavior of synthetic Al–Zn binary alloys

Development of a heat treatment for increasing the mechanical properties and stress corrosion resistance of 7000 Al alloys

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