Positron lifetimes and lineshape factors in deformed copper

Dauwe, C.; Dorikens, M.; Dorikens‐Vanpraet, L.; Segers, D.

doi:10.1007/bf00928222

Cited by 54 publications

(20 citation statements)

References 13 publications

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“…(6) we have defined a defect density as the number of trapping sites per unit volume. Dislocation density is generally expressed as length per unit volume, ρ (cm −2 ), 10,15 where the defects density is related to dislocation density according to Eq. (7).…”

Section: Resultsmentioning

confidence: 99%

Detecting Defects in Aircraft Materials by Nuclear Technique (Pas)

Badawi

2005

Surf. Rev. Lett.

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Positron annihilation spectroscopy (PAS) is one of the nuclear techniques used in material science. The present measurements are used to study the behavior of defect concentration in one of the most important materials aluminum alloys which is the 7075 alloy. It has been shown that positrons can become trapped at imperfect locations in solids and their mean lifetime can be influenced by changes in the concentration of such defects. No changes have been observed in the mean lifetime values after the saturation of defect concentration. The mean lifetime and trapping rates are studied for samples deformed up to 58.3%. The concentration of defect range vary from 10 15 to 10 18 cm −3 at the thickness reduction from 2.3 to 58.3%. The dislocation density varies from 10 8 to 10 11 cm/cm 3 .

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Section: Resultsmentioning

confidence: 99%

Detecting Defects in Aircraft Materials by Nuclear Technique (Pas)

Badawi

2005

Surf. Rev. Lett.

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“…This agrees with earlier findings that the lifetime of positrons trapped in the dilatational zone of an edge dislocation at low temperature is just slightly smaller than that of a single vacancy in the same material. [23][24][25] Measurements at low temperatures are however not convenient for nondestructive testing purposes.…”

Section: B Positron Annihilation In Plastically Deformed Metalsmentioning

confidence: 99%

Nondestructive monitoring of fatigue damage evolution in austenitic stainless steel by positron-lifetime measurements

Holzwarth

Schaaff

2004

Phys. Rev. B

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Positron-lifetime measurements have been performed on austenitic stainless steel during ͑i͒ stress-and ͑ii͒ strain-controlled fatigue experiments for different applied stress and strain amplitudes, respectively. For this purpose a generator-detector assembly with a 72 Se/ 72 As positron generator ͓maximum activity 25 Ci ͑0.9 MBq͔͒ has been mounted on mechanical testing machines in order to measure the positron lifetime without removing the specimens from the load train. The average positron lifetime has been determined by a ␤ ϩ Ϫ␥ coincidence. The feasibility to use the average positron lifetime for monitoring the evolution of fatigue damage and to predict early failure has been examined. In strain-and stress-controlled experiments the average positron lifetime shows a pronounced increase within the first 10% and 40% of the fatigue life, respectively. In stress-controlled experiments the average positron lifetime at failure depends significantly on the applied stress amplitude. In strain-controlled experiments significantly different positron lifetimes for different applied plastic strain amplitudes are obtained within the first 1.000 fatigue cycles, whereas differences get wiped out during further cycling until failure.

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“…where JLL(T) is the trapping rate, C the concentration of defects (considered constant), 12 and l/x / the positron lifetime. Curve A in Fig.…”

Section: + Li(t)c/\ F >mentioning

confidence: 99%

“…12 The deformed samples were allowed to age for several weeks prior to measurement, to allow monovacancies to anneal out, and then etched. Two specimens were measured: (A) One specimen with a defect concentration produced by hammering the specimen to reduce its thickness by about 10% and (B) an undeformed annealed sample.…”

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Evidence for Temperature Dependence of Positron Trapping Rate in Plastically Deformed Copper

Rice-Evans¹,

Hlaing²,

Chaglar³

1976

Phys. Rev. Lett.

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FIG. 2. Wave-vector components for minima of curves in Fig. 1. Solid lines are circles corresponding to zeroth-order energy levels according to Eq. (5). Dot size indicates estimated error.tually the far more prevalent situation. As further examples, the [/-0, l] and [j-1, 0] pairs cross at (^ = 45° with no discernible perturbations, as do the I j -0, 1J and [ j -0, Tj pairs at cp = 0°. In fact, such crossings are of great assistance in identifying the minima and determining the energy values needed for the radii of the circles drawn in Fig. 2.Thanks are due to the National Science Foundation and to the Applied Research Laboratory of The Pennsylvania State University for their support of this work, and to Professor Eric Thompson for preprints and discussions of his work in advance of publication.son calculated a splitting of about 6° for LiF, based on a model potential with several empirically fitted parameters. Our experimental results on NaF (Fig. 1) show splittings of the same order of magnitude. However, rather than a simple crossing of two otherwise isolated levels, we see that the situation is complicated by the presence of numerous other zeroth-order levels in the same vicinity. The observed positions of the minima suggest mixing of the following pairs of zeroth-order states: [0-1, Oj and [0-1, T], [0-1, l]and [1-1,0], and [ 1-1,1] and [ 1-1,0] in the notation [j-m 9 n].These pairs are all connected by reciprocal-lattice vectors of the (0, 1) type.On the other hand, the [0-0, 2] level has no discernible effect, as it is connected with the others by longer reciprocal-lattice vectors.

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Positron lifetimes and lineshape factors in deformed copper

Cited by 54 publications

References 13 publications

Detecting Defects in Aircraft Materials by Nuclear Technique (Pas)

Detecting Defects in Aircraft Materials by Nuclear Technique (Pas)

Nondestructive monitoring of fatigue damage evolution in austenitic stainless steel by positron-lifetime measurements

Evidence for Temperature Dependence of Positron Trapping Rate in Plastically Deformed Copper

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