A kinetic analysis of AlAl3Li unmixing

Livet, F.; Bloch, Daniel R.

doi:10.1016/0036-9748(85)90225-x

Cited by 43 publications

(12 citation statements)

References 6 publications

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“…[6] This approach has already been applied in several binary systems. [11][12][13][14][15] The interface energy can also be obtained from measurements of the matrix solute concentration during coarsening, together with the mean precipitate size, using the Gibbs-Thompson equation. This direct application of the Gibbs-Thompson equation has been directed at Al-Li [16] and Cu-Ni-P systems.…”

mentioning

confidence: 99%

Coarsening of Al3Sc precipitates in an Al-0.28 wt pct Sc alloy

Watanabe

Kondo

Monzen

2004

Metall Mater Trans A

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The Ostwald ripening of Al 3 Sc precipitates in an Al-0.28 wt pct Sc alloy during aging at 673, 698, and 723 K has been examined by measuring the average size of precipitates by transmission electron microscopy (TEM) and the reduction in Sc concentration in the Al matrix with aging time, t, by electrical resistivity. The coarsening kinetics of Al 3 Sc precipitates obey the t 1/3 time law, as predicted by the Lifshitz-Slyozov-Wagner (LSW) theory. The kinetics of the reduction of Sc concentration with t are consistent with the predicted t Ϫ1/3 time law. Application of the LSW theory has enabled independent calculation of the Al/Al 3 Sc interface energy, ␥, and volume diffusion coefficient, D, of Sc in Al during coarsening of precipitates. The Gibbs-Thompson equation has been used to give a value of ␥ using coarsening data obtained from TEM and electrical resistivity measurements. The value of ␥ estimated from the LSW theory is 218 mJ m Ϫ2 , which is nearly identical to 230 mJ m Ϫ2 from the Gibbs-Thompson equation. The pre-exponential factor and activation energy for diffusion of Sc in Al are determined to be (7.2 Ϯ 6.0) ϫ 10 Ϫ4 m 2 s Ϫ1 and 176 Ϯ 9 kJ mol Ϫ1 , respectively. The values are in agreement with those for diffusion of Sc in Al obtained from tracer diffusion measurements.dependence of the coarsening behavior of precipitates in an Al-0.3 wt pct Sc alloy aged at 573 to 723 K. In addition, the diffusivity of Sc in Al is obtained from coarsening experiments. Iwamura and Miura [10] have examined the coarsening behavior of Al 3 Sc precipitates in an Al-0.2 wt pct Sc alloy at 673 to 763 K on the basis of TEM observations with the numerical model. The radius for coherent/semicoherent transition of the precipitates is determined from TEM images as 15 to 40 nm. The average radius, r, of the Al 3 Sc precipitates obeys the r 3 growth law both in the coherent stage (r Ͻ 15 nm) and in the semicoherent stage (r Ͼ 40 nm). However, in the intermediate stage, where coherent and semicoherent precipitates coexist (15 Ͻ r Ͻ 40 nm), coarsening is delayed.By measuring independently both the growth rate of precipitates and the rate of depletion of the matrix supersaturation during coarsening of the precipitates, independent reliable values of the matrix/precipitate interface energy and the diffusion coefficient of solute in the matrix can be determined from coarsening data alone. [6] This approach has already been applied in several binary systems. [11][12][13][14][15] The interface energy can also be obtained from measurements of the matrix solute concentration during coarsening, together with the mean precipitate size, using the Gibbs-Thompson equation. This direct application of the Gibbs-Thompson equation has been directed at Al-Li [16] and Cu-Ni-P systems. [17] In this work, the coarsening kinetics of the Al 3 Sc precipitates in an Al-0.28 wt pct Sc alloy aged at 673, 698, and 723 K have been investigated. The Al/Al 3 Sc interface energy, ␥, and the diffusivity of Sc in Al have been independently derived from measurements o...

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mentioning

confidence: 99%

Coarsening of Al3Sc precipitates in an Al-0.28 wt pct Sc alloy

Watanabe

Kondo

Monzen

2004

Metall Mater Trans A

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“…Both behaviours (ie pcct'!3 and G c r t ' I 3 ) are observed in the AI--Li concentrated alloys (Livet and Bloch, 1985). (Figure 10) shows the time evolution of p and 6c in /I1 10.5atO/Li alloy at 150°C.…”

Section: Y=omentioning

confidence: 87%

“…One example is shown in ( Figure 5): within the incubation period, cycling between two temperatures changes reversibly the plateau level, the higher the plateau level the lower is the supersaturation (or AT), which in terms of the quantification given previously is related to an increase of the Incubation periods are observed also in the case of much deeper quenches. In Al-Li('l.S%at) at 15OoC, no evidence of precipitation is found during 1 hour of "in-situ" small angle scattering experiments (Livet and Bloch, 1985), see (Figure 9). Here, the final volume fraction of the precipitates is about 0.18.…”

Section: Kinetics Regimesmentioning

confidence: 92%

Dynamics of phase separation in metallic systems

et al. 1991

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Various aspects of the time evolution of metallic solid solutions quenched under a miscibility gap and evolving towards equilibrium are considered. After a survey of the various theories describing the phase separation, the informations given by the experiments are described. The experimental results are discussed in terms of patterns and morphologies of the microstructures and of various kinetics regimes occurring at different quench depths: nucleation-growth of heterophase fluctuations, coarsening of well defined second phase particles, homophase fluctuations or spinodal decomposition, interconnected microstructure. Multicomponent alloys are finally considered.

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“…The metastable solubility of Li at room temperature has been reported as 5at% (Schiffini and co-workers [27,28]) and 2.3 at% [29] for binary Al-Li and as 5.4at% [16] and 1.6at% [17] for quaternary Al-Li-Cu-Mg alloys.…”

Section: Addition Of Mg Tomentioning

confidence: 99%

Embrittlement of Al–Li–Cu–Mg alloys at slightly elevated temperatures: microstructural mechanisms of hardening

Starink

Hobson

Sinclair

et al. 2000

Materials Science and Engineering: A

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When underaged, damage tolerant Al-Li based alloys are exposed to slightly elevated temperatures (60 to 100ºC), their strength increases and toughness decreases. To study the first stages of this process, 8090 sheet in three underaged heat treatment conditions, including T3, T81 and a multistage temper, was exposed for 1000 h at 70°C. Using a model for strengthening in combination with a quantitative analysis of differential scanning calorimetry data, it is shown that strengthening can be explained by an increase in the volume fraction of the δ' phase and, to a lesser extent, to the formation of Guinier-Preston (GPB) zones. For the T3 temper, coarsening of δ' precipitates is the main strengthening mechanism during exposure at 70ºC. The solvus of δ' and GPB, which to a large extent defines this embrittlement, is discussed. Toughness reduction during exposure at slightly elevated temperatures can be minimised via a multi stage temper or via a reduction of the Li content of the alloy.

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A kinetic analysis of AlAl3Li unmixing

Cited by 43 publications

References 6 publications

Coarsening of Al3Sc precipitates in an Al-0.28 wt pct Sc alloy

Coarsening of Al3Sc precipitates in an Al-0.28 wt pct Sc alloy

Dynamics of phase separation in metallic systems

Embrittlement of Al–Li–Cu–Mg alloys at slightly elevated temperatures: microstructural mechanisms of hardening

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