On the decomposition behaviour of Al-4.5 at% Zn-2 to 3 at% Mg alloys during continuous heating

Radomsky, M.; Kabisch, O.; Löffler, H.; Lendvai, J.; Ungár, Tamás; Kovács, I.; Honyek, G.

doi:10.1007/bf00611473

Cited by 39 publications

(10 citation statements)

References 2 publications

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“…tion tends to be rather scattered, either within a range of 20 Thin foils for TEM were prepared by conventional ЊC to 70 ЊC [14,15,16,20,21] or close to or above 100 ЊC. [22,23] mechanical thinning and twin-jet electropolishing, and…”

Section: Methodsmentioning

confidence: 99%

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Differential scanning calorimetry and electron diffraction investigation on low-temperature aging in Al-Zn-Mg alloys

Jiang

Taftø

Noble

et al. 2000

Metall Mater Trans A

135

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Differential scanning calorimetry (DSC) has been combined with transmission electron microscopy (TEM) to investigate the low-temperature decomposition processes taking place in an Al-5 wt pct Zn-1 wt pct Mg alloy. It was confirmed that two types of GP zones, i.e., GP(I) (solute-rich clusters) and GP(II) (vacancy-rich clusters), formed independently during decomposition of the supersaturated solid solution. The GP(I) zones form at a relatively low aging temperature and dissolve when the aging temperature is increased. The GP(II) zones are stable over a wider range of temperatures. To investigate the nature of the zones in the Al-Zn-Mg alloy, differential scanning calorimetry and transmission electron microscopy have also been carried out on binary Al-Zn alloys containing 5 wt pct and 10 wt pct Zn. In these Al-Zn alloys, GP zones formed rapidly during quenching, and they gave rise to characteristic electron diffraction patterns identical to those from GP(II) in the Al-ZnMg alloy system, implying that GP(II) zones in Al-Zn-Mg alloys are very similar to the zones formed in binary Al-Zn alloys. Thus, it is likely that GP(II) zones in Al-Zn-Mg alloys are zinc-rich clusters. In the Al-5 wt pct Zn-1 wt pct Mg alloy, both GP(I) and GP(II) were found to transform to Ј and/ or particles during heating in the differential scanning calorimeter. The Ј was also observed to form after prolonged isothermal aging of the Al-Zn-Mg alloy at 75 ЊC or after short aging times at 125 ЊC.

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Section: Methodsmentioning

confidence: 99%

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25] However, there is still a great deal of uncertainty about the nature of the zones and clusters that …”

Section: Introductionmentioning

confidence: 99%

Differential scanning calorimetry and electron diffraction investigation on low-temperature aging in Al-Zn-Mg alloys

Jiang

Taftø

Noble

et al. 2000

Metall Mater Trans A

135

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“…This indicates that the solid solution has attained the maximum degree of decomposition, and that the phase present should be incoherent with the underlying lattice. Consequently, the only precipitate in the annealed state should be the incoherent t/phase (MgZn~) [1, [6][7][8][9]. Therefore the single endothermic peak in the DTA curve for this condition should represent the dissolution of the t/ phase [1,2].…”

Section: Resultsmentioning

confidence: 99%

“…To gain confidence in these techniques as the main method to characterize the matrix precipitate of an alloy in a particular metallurgical state the data obtained from thermal analysis (DTA or DSC) have to be correlated with those obtained by other well established techniques such as TEM among others. This has been done in recent years on a variety of alloys and tempers [6,[8][9][10]. These studies will hopefully build up a solid basis for the use of DTA and DSC in the rapid identification of the matrix microstructure of aluminium alloys [6].…”

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confidence: 99%

Interpretation of DTA curves for microstructure characterization of a commercial Al-Zn-Mg alloy (7015), aided by conductivity and hardness measurements

Cordovilla

Louis

1982

Journal of Thermal Analysis

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Hardness and conductivity measurements are shown to be useful to help the interpretation of differential thermal analysis (DTA) curves for aluminium alloys in different metallurgical states. In particular, a commercial A1--Zn--Mg alloy (7015) is studied in four metallurgical conditions. The results of the present analysis are compared with recent studies carried out by other authors on similar alloys by means of transmission electron microscopy (TEM) and differential scanning calorimetry (DSC).Thermal analysis techniques are rapidly becoming a valuable tool in identifying solid state reactions in aluminium alloys [1][2][3][4][5][6][7][8][9][10]. To gain confidence in these techniques as the main method to characterize the matrix precipitate of an alloy in a particular metallurgical state the data obtained from thermal analysis (DTA or DSC) have to be correlated with those obtained by other well established techniques such as TEM among others. This has been done in recent years on a variety of alloys and tempers [6,[8][9][10]. These studies will hopefully build up a solid basis for the use of DTA and DSC in the rapid identification of the matrix microstructure of aluminium alloys [6]. A further advantage of thermal analysis is the possibility of studying quantitatively the kinetics of solid state reactions in alloys [6,10].It is the purpose of this paper to present a study of the microstructure of a commercial A1-Zn-Mg alloy (7015) in different metallurgical states, by means of DTA, hardness and conductivity measurements. The matrix microstructure of A1-Zn-Mg alloys in different metallurgical states are being currently studied [1,2,[6][7][8][9][10][11][12][13][14] and, although some points are still controversial, the main questions concerning precipitation processes in these alloys have already been clarified. Although depending on different factors a large number of metastable phases have been identified [7,11 ], it is nowadays widely accepted that precipitation in the 7000 series (A1-Zn-Mg and A1-Zn-Mg-Cu alloys) takes place in the following simple sequence [2,12]: supersaturated solid solution =~ Guinier-Preston (G. P.) zones ~ coherent or semicoherent t/' phase (MgZn2) =, incoherent r/phase (MgZn~). Recently a metastable phase diagram for this sequence has been inferred from different experimental data [11 ]. The description of the characteristics of the above mentioned phases can be found elsewhere [14], here suffices it to note that their relative thermal stability is as follows t/ > t/' > GP zones.In this work the main emphasis will be placed on the correlation of the data obtained from DTA with those given by the other two measurements. This is o r . Thermal AnaL 24, 1982

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“…There are a number of papers which deal with the formation of Guinier-Preston (GP) zones at room temperature (RT) in the M-Zn-Mg system and with the reversion of these zones at higher temperatures, as well as with the nature of the processes following the reversion [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Many papers have dealt with the influence of small Mg additions on the zone formation in A1-Zn alloys [15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

The influence of Mg content on the formation and reversion of Guinier-Preston zones in Al-4.5 at % Zn-x Mg alloys

et al. 1981

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The influence of Mg concentrations on the dissolution of Guinier-Preston (GP) zones formed at room temperature (RT) and on the formation of more stable phases has been investigated during continuous heating of AI-4.5 at% Zn-xMg alloys. The Mg content was varied from 0.05 to 3 at %. After different aging periods at RT, calorimetric investigations were carried out at heating rates of 40 and 80 ~ C min -I . In the case of alloys with a lower Mg content (x ~< 0.5 at %) only the dissolution of GP zones could be observed during the heating, whereas in the case of alloys with a higher Mg content the formation of the ~?'-phase started before the total dissolution of GP zones and at higher temperatures the formation of the r/-phase also took place. These phases were identified by transmission electron microscopy. The heat-of-solution of GP zones shows saturation as a function of RT aging time. The time needed for the saturation increased monotonously with increasing Mg content. The reversion of zones was followed by in situ X-ray small angle scattering measurements. The change of the total scattered intensity was measured during continuous heating at a rate of 40 ~ C min -1 . These investigations have confirmed the results of the calorimetric measurements which indicate that the total dissolution of zones takes place only in the case of the alloys with a Mg content lower than 0.5 at%. In the case of alloys with a Zn concentration of 4.5 at % studied here, 1 at % Mg is sufficient to initiate the formation of more stable phases during the reversion of zones.

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On the decomposition behaviour of Al-4.5 at% Zn-2 to 3 at% Mg alloys during continuous heating

Cited by 39 publications

References 2 publications

Differential scanning calorimetry and electron diffraction investigation on low-temperature aging in Al-Zn-Mg alloys

Differential scanning calorimetry and electron diffraction investigation on low-temperature aging in Al-Zn-Mg alloys

Interpretation of DTA curves for microstructure characterization of a commercial Al-Zn-Mg alloy (7015), aided by conductivity and hardness measurements

The influence of Mg content on the formation and reversion of Guinier-Preston zones in Al-4.5 at % Zn-x Mg alloys

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