Annealing spectrum of precipitating Al-Li alloys

Kamel, R.; Ali, A. R.; Farid, Z.

doi:10.1002/pssa.2210450103

Cited by 10 publications

(3 citation statements)

References 5 publications

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“…3 a and b). The activation energy of stage 111 was found by using the cross-cut method, while energies activating the annealing processes of stages IV and V were determined from equivalent times and temperatures, required to attain a particular stage of recovery specified by the &-1 peak position [8].…”

Section: Resultsmentioning

confidence: 99%

On the Behaviour of Interaction of Copper Atoms with Lattice Defects in Quenched and Cold-Worked NiCu Alloys

Ali

1985

phys. stat. sol. (a)

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Isochronal annealing experiments in the recovery regions of stage 111, IV, and V are performed on Xi-Cu alloys after quenching and cold-working, using internal friction and electrical resistance measurements. The annealing stage I11 appears only in the recovery of cold-worked sample, activated by 1.18 eV, is inferred to the release of interstitials trapped on Cu atoms. The binding energy between the interstitial and Cu atom is found to be 0.12 eV. The recovery stage IV, attributed to the annealing of vacancy-Cu pairs with the possible formation of complex aggregates, is found to be activated by an energy 1.58 eV. The mechanisms responsible for these two recovery stages are enhanced by increasing Cu atoms content in the matrix. The annealing stage V occurred in the recovery spectrum of both quenched and cold-worked Ni-Cu alloys. For quenched samples this stage is discussed as annealing of vacancy clusters formed during the quenching, while for cold-worked samples, stage V is attributed to recrystallization. Mittels Messungen der innerenReibung und des elektrischen Widerstnnds werden isochrone Aiisheilexperimente im Erholungsbereich der Stufen 111, I V nnd V an Ni-Cu-Legierungen nacli Abschrecken und Kaltwalzen durchgefiihrt. Die Ausheilstufe 111, die nur bei der Erholung von kaltgewalzten Proben mit einer Aktivicrungsenergie von 1,18 eV auftritt, wird der Freisetzung von 1nt.erstitials zugeschrieben, die an Cu-Atomen angehaft.et sind. Die Bindungsenergie zwischen dcm Int,erstitial nnd dem Cu-Atom wird z u 0,12 eV besbimmt. Die Erholungsstnfe IV, die der Ausheilung von 1,ecrstellen-Cu-Paaren mit der moglichen Bildung von komplexen Aggregaten zugeschrieben wird, besitzt eine Aktivierungsenergie von 1,58 eV. Der fur diese beiden Erholungsstufen verxntwortliche Mechanismas nimmt mit wachsendem Cu-Atomgehalt in der Matrix zu. Die Ausheilstufe V tritt im Erholungsspektrum sowohl von abgeschreckten als auch von k d tgewalzten Xi-Cu-Legierungen auf. Fur a bgeschreckte Proben wird diese Stufe diskutiert als ;\uslrcilung von Leerstellenclnstern, die wtihrend der Abschreckung gebildet werden, wahrend fiir kaltgewalzte Proben die Stufe V eincr Kelrrist'allisation zugeordnet wird. lnt.roductionAttention has recently been focussed on the effect of impurity atoms 011 the annealing spectrum of quenched and cold-worked Ni [l, 21. It, has been found that small amounts of impurities can have a strong influence on the recovery spectrum and attempts have been made to explain this in terins of impurity trapping point, defects and hence effectively limiting the concentration available for point defect, cluster formation [3]. Thus, it w a s the purpose of this investigation to study in detail the influence of systematically varied Cu contents in Xi matrix on internal friction and electrical resistivity. I t was expected that from such measurements more information could be obtained on both t,he nat,ure of defects part.icipating in the various recovery processes and also on t,he formation sequence and relative stability of corresponding d...

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Section: Resultsmentioning

confidence: 99%

On the Behaviour of Interaction of Copper Atoms with Lattice Defects in Quenched and Cold-Worked NiCu Alloys

Ali

1985

phys. stat. sol. (a)

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“…Above 450 ~ the loss in Li concentration in the matrix seems to be responsible for the observed increase in lattice parameter and decrease in electric resistivity. Duc to the existence of interaction energy between Li atoms and dislocations [1,3], stabilization of dislocations takes place asa process of anneal hardening [11], which leads to the observed increase in hardness above 450 ~…”

Section: Discussionmentioning

confidence: 99%

“…Samples of Al-10 at Yo Li were produced b y a m e t h o d previously deseribed [3]. Quenehing from 560 ~ to room t e m p e r a t u r e with a rate of 3 • 103 ~ was earried out to bring the samples in a m e t a s t a b l e s t a n d a r d eondition of solid solution.…”

Section: Methodsmentioning

confidence: 99%

The role of lithium atoms in the structural changes in Al−Li alloy

et al. 1979

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The dependence of structural changes in preeipitating Al-10 at% Li alloy on the annealing temperatures as traeed by X-rays, eleetrie resistivity and mierohardness measurements revealed the formation and subsequent dissolution of Al-Li preeipitates in the temperature range of 25--500 ~ The observed variations were attributed to the effect of the annealing temperature on the behaviour of Li atoms within the Al matrix. The inerease of the Li concentration in the matrix due to the dissolution of Al-Li precipitates, being 3.75 at ~/o Li as obtained from X-ray measurements agreed well with the value 4.0 at % Li obtained from resistivity measurements. I n t r o d u c t i o n I t has been reported [1] t h a t in supersaturatedAl-Li alloys, the fl-phase (Al-Li) preeipitated b y annealing in the t e m p e r a t u r e range of 150--300 oC and dissolved at higher t e m p e r a t u r e s leads to the dispersion of the exeess Li atoms b y diffusion t h r o u g h the matrix. Sueh struetural ehanges affeeted largely b o t h the eleetrieal [2] and meehanieal [1] properties of the alloy.The present work airas at traeing the role of Li a t o m s in the Al m a t r i x in the struetural ehanges of different t e m p e r a t u r e s in the alloy from X -r a y diffraetion tests. Also, it is aimed at relating the variations in eleetrie resist i v i t y and mierohardness to these struetural ehanges. ExperimentalSamples of Al-10 at Yo Li were produced b y a m e t h o d previously deseribed [3]. Quenehing from 560 ~ to room t e m p e r a t u r e with a rate of 3 • 103 ~ was earried out to bring the samples in a m e t a s t a b l e s t a n d a r d eondition of solid solution. Isoehronal annealings were done b y heat pulses of 10 min at t e m p e r a t u r e s sueeessively increasing in steps of 20 ~ After eaeh heat pulse the resistanee of the samples was measured at room t e m p e r a t u r e using a standard potentiometrie m e t h o d [4]. A d u m m y sample helped to aeeount for the effeet of t e m p e r a t u r e variation. Microhardness m e a s u r e m e n t s I~ Acta Physica -,4cademiae Scientiarum Hungaricae 46, 1979

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On the recovery of quenched and irradiated dilute Al-Li alloys

Kamel

Ali

Farid

1978

Phys. Stat. Sol. (a)

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The annealing spectra of quenched and irradiated pure Al and dilute Al‐Li alloys containing 2.5 and 4.5 at% Li are isochronally tested in the temperature range 25 to 400 °C, by using both resistivity and internal friction measurements. The annealing spectrum of pure Al involves two recovery processes centred near room temperature and 160 °C. The first process is inferred to the coagulation of vacancies to form vacancy platelets and its subsequent collapse to give dislocation loops. The second process is attributed to the subsequent growth of the dislocation loops by dislocation climb. The annealing spectra of the quenched dilute Al‐Li alloys, shows three internal friction peaks in the temperature ranges 25 to 120, 120 to 200, and 200 to 300°C, characterized by activation energies 0.7, 1.3, and 1.44 eV, respectively. The first annealing band is ascribed to the annealing of vacancy‐Li couples formed during the quenching with the possible formation of GP zones. The second band is attributed to lithium atom dispersion. by normal diffusion from aggregates. The third annealing stage is thought to be due to the tendency of solute atoms to cluster in the matrix in the form of (AlLi) particles.

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Annealing spectrum of precipitating Al-Li alloys

Cited by 10 publications

References 5 publications

On the Behaviour of Interaction of Copper Atoms with Lattice Defects in Quenched and Cold-Worked NiCu Alloys

On the Behaviour of Interaction of Copper Atoms with Lattice Defects in Quenched and Cold-Worked NiCu Alloys

The role of lithium atoms in the structural changes in Al−Li alloy

On the recovery of quenched and irradiated dilute Al-Li alloys

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