A comment on ‘The annealing kinetics of double dislocation loops in thin foils'

It has been shown that dislocation loops can be nucleated and grown in thin foils made from quenched specimens of magnesium and zinc. Observations are presented which indicate that the surfaces of the thin foils are sealed with an oxide film. Freely diffusing vacancies can only escape from the foil where this oxide film has become locally ruptured, exposing the metal surface. The loops are usually faulted, with b = R = 1/6 <2023>. Occasionally unfaulted loops, with b = <0001>, are observed. An analysis of the kinetics of climb of the faulted loops provides estimates of the stacking fault energy (corresponding to a single violation of the next-nearest-neighbour stacking sequence). These values are, for magnesium, 280 ± 100 erg/ cm 2 and, for zinc, 300 ± 150 erg/cm 2 . Factors influencing the climb rate are discussed.

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The annealing kinetics of double dislocation loops in thin foils

Philosophical Magazine ◽

10.1080/14786437508229287 ◽

1975 ◽

Vol 31 (1) ◽

pp. 87-96 ◽

Cited By ~ 3

Author(s):

H. O. K. Kirchner

Keyword(s):

Dislocation Loops ◽

Thin Foils ◽

Kinetics Of

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The formation and growth of vacancy loops in magnesium

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1968.0175 ◽

1968 ◽

Vol 307 (1488) ◽

pp. 71-81 ◽

Cited By ~ 22

Keyword(s):

Surface Oxidation ◽

Stacking Fault ◽

Stacking Fault Energy ◽

Dislocation Loops ◽

Temperature Range ◽

Vacancy Loops ◽

A Value ◽

Thin Foils ◽

Contrast Analysis ◽

Kinetics Of

Single, double and multi-layered dislocation loops have been observed in thin foils of quenched magnesium, and the structure of the loops established by contrast analysis. On annealing in the temperature range 150 to 200°C the loops are observed to grow as a result of the production of vacancies by surface oxidation of magnesium. The kinetics of loop growth have been analysed and a value of 125 ± 25 erg/cm 2 for the stacking fault energy obtained.The reliability and significance of the value in governing the properties of magnesium is discussed.

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Direct observations of radiation-enhanced transformations in glass

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075543 ◽

1983 ◽

Vol 41 ◽

pp. 354-355

Author(s):

J. F. DeNatale ◽

D. G. Howitt

Keyword(s):

Glass Matrix ◽

Diffusion Mechanism ◽

Bubble Formation ◽

Silicate Glasses ◽

Phase Decomposition ◽

Direct Observations ◽

Thin Foils ◽

Oxygen Bubble ◽

Electron Energy Loss ◽

Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

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Effets of surfaces on precipitate morphology in irradiated thin foils

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110416 ◽

1978 ◽

Vol 36 (1) ◽

pp. 654-655

Author(s):

D.I. Potter ◽

A. Taylor

Keyword(s):

Ion Irradiation ◽

Dark Field Image ◽

Thin Foil ◽

Dark Field ◽

Al Alloy ◽

Bright Field Image ◽

Dislocation Loops ◽

Precipitate Morphology ◽

Thin Foils

Thermal aging of Ni-12.8 at. % A1 and Ni-12.7 at. % Si produces spatially homogeneous dispersions of cuboidal γ'-Ni3Al or Ni3Si precipitate particles arrayed in the Ni solid solution. We have used 3.5-MeV 58Ni+ ion irradiation to examine the effect of irradiation during precipitation on precipitate morphology and distribution. The nearness of free surfaces produced unusual morphologies in foils thinned prior to irradiation. These thin-foil effects will be important during in-situ investigations of precipitation in the HVEM. The thin foil results can be interpreted in terms of observations from bulk irradiations which are described first.Figure 1a is a dark field image of the γ' precipitate 5000 Å beneath the surface(∿1200 Å short of peak damage) of the Ni-Al alloy irradiated in bulk form. The inhomogeneous spatial distribution of γ' results from the presence of voids and dislocation loops which can be seen in the bright field image of the same area, Fig. 1b.

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Precipitation in thin foils of al-4wt.% Cu alloy, 11. Growth kinetics of θ precipitates

Scripta Metallurgica ◽

10.1016/0036-9748(74)90358-5 ◽

1974 ◽

Vol 8 (11) ◽

pp. liii

Author(s):

S.K. Kang ◽

C. Laird

Keyword(s):

Growth Kinetics ◽

Cu Alloy ◽

Thin Foils ◽

Kinetics Of

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Amorphization Kinetics of Zr (Cr,Fe)2 Under Ion Irradiation

MRS Proceedings ◽

10.1557/proc-279-517 ◽

1992 ◽

Vol 279 ◽

Cited By ~ 4

Author(s):

A. T. Motta ◽

L. M. Howe ◽

P. R. Okamoto

Keyword(s):

Neutron Irradiation ◽

Ion Irradiation ◽

Ion Beam ◽

National Laboratory ◽

Argonne National Laboratory ◽

Matrix Interface ◽

Thin Foils ◽

Intermetallic Precipitates ◽

Kinetics Of

ABSTRACTThin foils of Zircaloy-4 were irradiated with 350 KeV 40Ar ions in the dual ion beam/HVEM facility at Argonne National Laboratory at 300 – 650 K. The irradiation-induced araorphization of the intermetallic precipitates Zr (Cr, Fe)2 and Zr2 (Ni, Fe) was studied in situ. For Zr (Cr,Fe)2 precipitates the dose-to-amorphization was found to increase exponentially with temperature, with a critical temperature of about 650 K. The amorphization morphology was shown to be homogeneous, with no preferential site for nucleation, in contrast to neutron-irradiation amorphization which started at the precipitate-matrix interface. For Zr2 (Ni,Fe) precipitates it was found that amorphization occurred at 550 K and 600 K, whereas in neutron irradiation no amorphization has been observed at those temperatures. The results are discussed in the context of the previous experimental results of neutron and electron irradiation and likely amorphization mechanisms are proposed.

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