Accelerated helium bubble growth in aluminum in the presence of lead precipitates

Wright, Roger N.; Siclen, Clinton DeW. Van; Usmar, S.G.; Mochel, M. E.

doi:10.1016/0022-3115(91)90443-b

Cited by 12 publications

(8 citation statements)

References 9 publications

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“…Willertz and Shewmon (1970), Goodhew and Tyler (1981) and others have concluded that ledge nucleation may be the rate-limiting step in gas bubble growth by surface diffusion, since their calculated values for D, are orders-of-magnitude lower than those values suggested by Gjostein. The helium bubbles observed by Wright et al (1992) do not appear to remain faceted at the annealing temperatures, consistent with the results of Moore, Chattopadhyay and Cantor (1987) and Moore, Zhang and Cantor (1990), who monitored the change in equilibrium shape of lead inclusions in aluminium with increasing temperature. At room temperature, the lead particles are present as truncated octahedrons bounded by {loo} and { 11 l} facets.…”

supporting

confidence: 91%

“…Electron micrographs and energy-dispersive X-ray spectra taken at room temperature showed the lead to be present as small precipitates at preferred facets of the helium bubbles. Concurrent positron annihilation spectroscopy studies (Wright et al 1991, Usmar and confirmed the TEM observations of enhanced bubble growth in the alloy and, by the decrease in intensity of the long-lifetime component of the positron lifetime spectrum with increasing annealing temperature, suggested that the primary growth mechanism is bubble migration and coalescence.…”

Section: Q 3 Application To Experimental Resultssupporting

confidence: 57%

“…A gas bubble of lOnm radius thus requires a solid precipitate with 1'= 6.24 or 6-34 nm to cover the surface completely with an atomic monolayer of liquid lead or indium respectively. Wright et al (1992) show the precipitates at room temperature to be considerably smaller than this; however, the visible precipitates may simply represent impurity atoms in excess of those required to maintain coverage of the bubble surface by surface energy considerations. The applicability of the liquid dissolution diffusion process to the observed bubble behaviour is best assessed by solving eqn.…”

mentioning

confidence: 94%

“…fj 4. CONCLUDING REMARKS Without accurate knowledge of the amount of lead or indium associated with the helium bubbles observed by Wright et al (1992), interpretation of the enhanced bubble diffusion according to the liquid dissolution mechanism must be regarded as speculative. Furthermore, the calculations above, by their use of bulk liquid properties, do not take account of the two-dimensional nature of the liquid coating the bubble.…”

mentioning

confidence: 98%

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Enhanced diffusion of liquid-coated gas bubbles in solids

Siclen

Wright

1993

Philosophical Magazine A

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supporting

confidence: 91%

Section: Q 3 Application To Experimental Resultssupporting

confidence: 57%

mentioning

confidence: 94%

mentioning

confidence: 98%

See 2 more Smart Citations

Enhanced diffusion of liquid-coated gas bubbles in solids

Siclen

Wright

1993

Philosophical Magazine A

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“…This work was motivated by recent TEM and positron lifetime spectroscopy measurements indicating surprisingly rapid helium bubble growth in aluminum containing approximately 1 ppm by weight of lead [4,5]. Figure 1, adapted from Ref.…”

mentioning

confidence: 99%

Anomalous helium bubble diffusion in dilute aluminum alloys

1992

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Remarkably rapid Brownian motion of helium bubbles in aluminum alloyed with very low concentrations of lead and of indium has been observed in situ by hot-stage transmission electron microscopy. Bubble diffusion is enhanced as the impurity coats the bubble surfaces at annealing temperatures above the melting point of the impurity. The bubble diffusion coefficients calculated from video images of the bubble motion, and the corresponding surface diffusion coefficients, are orders of magnitude larger than diffusion coefficients determined from helium bubble growth experiments in pure aluminum.PACS numbers: 66.30.Jt, 66.30.Lw Helium atoms, being essentially insoluble in all metals [l], will agglomerate into bubbles that cause a deterioration of material properties. As such, the behavior of helium and other inert gases in fusion and fission reactor materials [where helium and heavier gas atoms are produced by the in,a) reaction and as fission products, respectively] is of considerable interest [2], particularly as reactor lifetimes are determined entirely by the structural damage due to gas bubbles and voids. Under such extreme conditions, bubble growth occurs as diffusing gas atoms, which produced continuously during irradiation, are captured, and by thermal-gradient-induced bubble migration and coalescence. In the absence of a continuous source of gas atoms and without temperature gradients, however, growth occurs by random bubble migration and coalescence, and, to a lesser extent, by Ostwald ripening [3].In this Letter we report in situ observations by hotstage transmission electron microscopy (TEM) of anomalously rapid helium bubble diffusion in aluminum containing a low concentration of lead, and in aluminum with a low concentration of indium, at annealing temperatures above the melting point of the impurity species. This work was motivated by recent TEM and positron lifetime spectroscopy measurements indicating surprisingly rapid helium bubble growth in aluminum containing approximately 1 ppm by weight of lead [4,5]. Figure 1, adapted from Ref.[4], shows bubble growth as a function of annealing time at 823 K for both the Pb-containing and Pb-free samples, and suggests that the accelerated bubble growth in the case of the dilute alloy may be due to extension of the migration-coalescence growth regime to much larger bubble sizes. Electron micrographs and energy dispersive x-ray spectra taken at room temperature show the lead to be present as small precipitates at preferred facets of the helium bubbles.To verify this hypothesis, samples of 99.999%-pure aluminum alloyed with 200 ppm by weight of lead, and separately, with 1000 ppm by weight of indium, were thinned to electron transparency and subsequently irradi-ated with 50-keV alpha particles at the HVEM-Tandem Facility at Argonne National Laboratory to produce a helium concentration of approximately 20 atomic ppm. The implanted samples were then annealed at 723-743 K for several minutes, during which time video recordings were made of spherical helium bubbles ...

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Submicrostructural and microstructural evolution of pure and oxygen contaminated vacuum melt-spun 99.9999% Al and Al:90 at p.p.m. C

Usmar

Wright

1992

J Mater Sci

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Accelerated helium bubble growth in aluminum in the presence of lead precipitates

Cited by 12 publications

References 9 publications

Enhanced diffusion of liquid-coated gas bubbles in solids

Enhanced diffusion of liquid-coated gas bubbles in solids

Anomalous helium bubble diffusion in dilute aluminum alloys

Submicrostructural and microstructural evolution of pure and oxygen contaminated vacuum melt-spun 99.9999% Al and Al:90 at p.p.m. C

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