STUDY OF TRAPPING RATE AND DEFECT DENSITY IN AlSi11.35Mg0.23 BY POSITRON ANNIHILATION TECHNIQUE

2004 ◽  
Vol 11 (04n05) ◽  
pp. 427-432 ◽  
Author(s):  
M. A. ABDEL-RAHMAN ◽  
M. S. ABDALLAH ◽  
EMAD A. BADAWI
Keyword(s):  
Positron Annihilation ◽  
Defect Density ◽  
Defect Concentration ◽  
Thickness Reduction ◽  
Trapping Rate ◽  
Positron Annihilation Lifetime ◽  
Maximum Value ◽  
Mean Lifetime ◽  
The Mean

The measurements of Positron Annihilation Lifetime Technique (PALT) have been performed on AlSi 11.35 Mg 0.23 Alloys. 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 change has been observed in the mean lifetime values at the saturation of defect concentration. The trapping rates of positrons can be determined for thickness reduction up to 11% for dislocation. The concentration of defect (ρ') range varies from 8.65×1015 to 2.35×1018 cm -3 up to the maximum value of strain (ε) 0.23.

DISLOCATION AND DEFECT DENSITIES BY PAT IN 2024 AIRCRAFT MATERIAL USING TWO DIFFERENT ACTIVITY SOURCES

2005 ◽  
Vol 12 (03) ◽  
pp. 463-468 ◽  
Author(s):  
M. A. ABDEL-RAHMAN ◽  
M. S. ABDALLAH ◽  
EMAD A. BADAWI
Keyword(s):  
Positron Annihilation ◽  
Material Science ◽  
Defect Concentration ◽  
2024 Aluminum Alloy ◽  
Nuclear Technique ◽  
Positron Annihilation Lifetime ◽  
Mean Lifetime ◽  
Aircraft Material ◽  
The Mean ◽  
Defect Densities

Positron annihilation lifetime spectroscopy (PALS) is a nuclear technique used in material science. Positron annihilation lifetime technique (PALT) measurements are used to study the behavior of defect concentration and dislocation density in a set of 2024 aluminum 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 concentrations of such defects. No changes were observed in the mean lifetime after defect concentration became saturated. The mean lifetime and trapping rates for the samples deformed up to 36.4 percent. The concentration of defects range from 1.133 × 1016 to 2.061 × 1018 cm-3 at strains from 1.7 to 22.7%.

Positron Lifetime in Deformed AlSi10.9Mg0.17Sr0.06 Alloys

2007 ◽  
Vol 261-262 ◽  
pp. 55-60 ◽  
Author(s):  
M.A. Abdel-Rahman ◽  
M.S. Abdallah ◽  
Emad A. Badawi
Keyword(s):  
Dislocation Density ◽  
Positron Annihilation ◽  
Material Science ◽  
Positron Lifetime ◽  
Defect Concentration ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime ◽  
Nuclear Techniques ◽  
Mean Lifetime ◽  
The Mean

Positron annihilation lifetime spectroscopy (PALS) is one of the nuclear techniques used in material science. (PALT) measurements are used to study the behaviour of the defect concentration in a set of AlSi10.9Mg0.17Sr0.06 alloys. It has been shown that positrons can become trapped at imperfect locations in solids, and that their mean lifetime can be influenced by changes in the concentration of such defects. No changes have been observed in the mean lifetime values following saturation of the defect concentration. The mean lifetime and trapping rates were studied for samples deformed up to 34.9 %. The concentrations of defects range vary from 5.194x1015 to 1.934x1018 cm-3 for thickness reductions of 2.2 to 34.9 %. The range of the dislocation density varies from 1.465x 108 to 5.454x1010 cm/cm3 over the same range of deformations.

DETECTING DEFECTS IN AIRCRAFT MATERIALS BY NUCLEAR TECHNIQUE (PAS)

2005 ◽  
Vol 19 (22) ◽  
pp. 3475-3482
Author(s):  
EMAD. A. BADAWI
Keyword(s):  
Aluminum Alloy ◽  
Dislocation Density ◽  
Material Science ◽  
Positron Annihilation Spectroscopy ◽  
Defect Concentration ◽  
Nuclear Technique ◽  
Nuclear Techniques ◽  
Mean Lifetime ◽  
The Mean ◽  
7075 Alloy

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 alloy — which is a 7075 alloy. It has been shown that positrons can become trapped in 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 were studied for samples deformed up to 58.3%. The concentration of defect range varies (from 1015 to 1018 cm-3) at the thickness reduction, (from 2.3 to 58.3%). The range of the dislocation density varies (from 108 to 1011 cm/cm3).

Defect Diffusion Models in NMR and Dielectric Relaxation

1978 ◽  
Vol 33 (11) ◽  
pp. 1294-1306 ◽  
Author(s):  
Rainer Kimmich ◽  
Gerhard Voigt
Keyword(s):  
Diffusion Process ◽  
Dielectric Relaxation ◽  
Diffusion Models ◽  
Defect Concentration ◽  
Relaxation Behaviour ◽  
Defect Diffusion ◽  
Rotational Isomers ◽  
Mean Lifetime ◽  
The Mean

The effect of diffusing defects such as vacancies, displacements, torsions, and rotational isomers on the nmr and dielectric relaxation behaviour is treated under various aspects. The influences of the dimensionality of the diffusion process, of the mutual hindrance, of the defect concentration, of the defect length and of the mean lifetime are derived and discussed.

DEFECT CONCENTRATION IN DEFORMED AlSiMgSr BY TRAPPING MODEL OF POSITRON

2005 ◽  
Vol 12 (04) ◽  
pp. 545-547 ◽  
Author(s):  
M. A. ABDEL-RAHMAN ◽  
M. S. ABDALLAH ◽  
EMAD A. BADAWI
Keyword(s):  
Dislocation Density ◽  
Defect Concentration ◽  
Thickness Reduction ◽  
Free State ◽  
Trapping Rate ◽  
Perfect Agreement ◽  
Lifetime Measurements ◽  
Trapping Model

This paper reports the results of lifetime measurements on deformed AlSiMgSr alloy. Using the trapping model, we obtained the value of 196.7 ps for the lifetime of the free state, and 210.5 ps for the trapped state. The specific trapping rate per unit defect concentration was calculated to be 0.2280 cm2 · s-1. The concentration of defects was 5.78×1017 cm -3 when thickness reduction was 18.2%. The dislocation density for the same thickness reduction is 1.63×1010 cm -2. We have compared these values with a previously used method1 and have obtained perfect agreement for both methods, demonstrating that this a very powerful tool for detecting and evaluating defect concentration.

INFLUENCE OF Mg CONTENT ON TRAPPING EFFICIENCY IN Al–Mg SYSTEM BY POSITRON ANNIHILATION SPECTROSCOPY

2006 ◽  
Vol 13 (04) ◽  
pp. 485-488
Author(s):  
EMAD BADAWI ◽  
M. A. ABDEL-RAHMAN ◽  
M. O. ABDELHAMED
Keyword(s):  
Positron Annihilation ◽  
Cross Section ◽  
Positron Annihilation Spectroscopy ◽  
Trapping Efficiency ◽  
Doppler Broadening ◽  
Deformation Degree ◽  
S Parameter ◽  
Mean Lifetime ◽  
The Mean ◽  
Mg Content

PLT and Doppler broadening S-parameter were used for Al – Mg alloy, namely 5005, 5051, 5052 and 5083. The trapping efficiency was estimated for the pervious alloys as 2.42 × 109, 2.29 × 109, 2.24 × 109 and 2.27 × 109 s -1 cm 3, respectively and the trapping cross-section was estimated to be as 2.66 × 10-16, 2.14 × 10-16, 2.10 × 10-16 and 3.51 × 10-16 cm 2, respectively. It is clear that the mean lifetime and S-parameter have the same behavior as a function of deformation degree and saturated at the same value of thickness reduction.

DETECTING DEFECTS IN AIRCRAFT MATERIALS BY NUCLEAR TECHNIQUE (PAS)

2005 ◽  
Vol 12 (01) ◽  
pp. 1-6 ◽  
Author(s):  
EMAD. A. BADAWI
Keyword(s):  
Aluminum Alloys ◽  
Dislocation Density ◽  
Material Science ◽  
Positron Annihilation Spectroscopy ◽  
Defect Concentration ◽  
Nuclear Technique ◽  
Nuclear Techniques ◽  
Mean Lifetime ◽  
The Mean ◽  
7075 Alloy

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 1015 to 1018 cm -3 at the thickness reduction from 2.3 to 58.3%. The dislocation density varies from 108 to 1011 cm/cm 3.

Effect of Mg Contents on Trapping Efficiency in Al-Mg System Using PAS

2007 ◽  
Vol 265 ◽  
pp. 7-11
Author(s):  
N.A. Kamel
Keyword(s):  
Cross Sections ◽  
Mg Alloys ◽  
Trapping Efficiency ◽  
Thickness Reduction ◽  
Doppler Broadening ◽  
Degree Of Deformation ◽  
S Parameter ◽  
Mean Lifetime ◽  
The Mean ◽  
Al Mg Alloys

PLT and the Doppler broadening S-parameter were used to characterize the Al-Mg alloys, AA5005, AA5051, AA5052 and AA5083. The trapping efficiencies of these alloys were estimated to be 2.42 x 109, 2.29 x 109, 2.24 x 109 and 2.27 x 109 s-1 cm3, respectively, and the corresponding trapping cross-sections were estimated to be 2.66 x 10-16, 2.14 x 10-16, 2.10 x 10-16 and 3.51 x 10-16 cm2. It was found to be very clear that the mean lifetime and S-parameter exhibited the same behaviour as a function of the degree of deformation, and that they saturated at the same degree of thickness reduction.

Probing the Activation Migration Enthalpies of Dislocations in 2024 Aircraft Material Using Nuclear and Electrical Techniques

2011 ◽  
Vol 316-317 ◽  
pp. 119-126 ◽  
Author(s):  
M.A. Abdel-Rahman ◽  
N.A. Kamel ◽  
Abdullah A. Refeay ◽  
Emad A. Badawi
Keyword(s):  
Activation Energy ◽  
Aluminum Alloys ◽  
Positron Annihilation ◽  
Isothermal Annealing ◽  
Materials Science ◽  
Thickness Reduction ◽  
Electrical Measurements ◽  
Positron Annihilation Lifetime ◽  
Nuclear Techniques ◽  
Aircraft Material

Positron annihilation lifetime (PAL) measurement is one of the most important nuclear techniques used in materials science. Electrical measurements are also used in materials science. Both PAL and electrical measurements were used here to determine the activation energy of migration of dislocations in one of the most important engineering aluminum alloys: 2024. Samples of 25% deformed (thickness reduction) material have been used for these studies. The isothermal annealing measurements were performed at 583, 603, 623 and 643K for both techniques. The activation energy of migration of the dislocation was found to be equal to 1.24 ± 0.08eV by using PAL measurements and to 1.35 ± 0.01eV by using the electrical technique.

Testing Natural Aging Effect on Properties of 6066 & 6063 Alloys Using Vickers Hardness and Positron Annihilation Lifetime Techniques

2010 ◽  
Vol 303-304 ◽  
pp. 107-112
Author(s):  
M.A. Abdel-Rahman ◽  
Alaa Aldeen Ahmed ◽  
Emad A. Badawi
Keyword(s):  
Positron Annihilation ◽  
Vickers Hardness ◽  
Natural Aging ◽  
High Strength ◽  
Aging Effect ◽  
Hardness Measurement ◽  
Solution Temperature ◽  
Positron Annihilation Lifetime ◽  
Solid Diffusion ◽  
Maximum Value

The aim of this work was to produce a high strength 6xxx series Aluminum alloy by adjusting the processing conditions, namely solutionizing and natural aging. It consists of heating the alloy to a temperature at which the soluble constituents will form a homogeneous mass by solid diffusion, holding the mass at that temperature until diffusion takes place, then quenching the alloy rapidly to retain the homogeneous condition. In the quenched condition, heat-treated alloys are supersaturated solid solutions that are comparatively soft and workable, and unstable, depending on composition. At room temperature, the alloying constituents of some alloys tend to precipitate from the solution spontaneously, causing the metal to harden in about four days. This is called natural aging. The mechanical characterization of heat treatable 6xxx (Al-Mg-Si-Cu based) 6066, 6063 wrought aluminum alloys was studied. Their effects were investigated in terms of microstructure using positron annihilation lifetime technique and mechanical properties by hardness measurements. The hardness is the Resistance of material to plastic deformation, which gives it the ability to resist deformed when a load is applied. The greater the hardness of the material, the greater resistance it has to deformation. Hardness measurement can be defined as macro-, micro- or nano- scale according to the forces applied and displacements obtained. Micro hardness is the hardness of a material as determined by forcing an indenter such as a Vickers indenter into the surface of the material under 15 to 1000 gf load; usually, the indentations are so small that they must be measured with a microscope. During this work we are monitoring the effect of natural aging on the properties of positron lifetime and Vickers hardness parameters. The Vickers hardness of 6066 alloy has a maximum value(80) after (10)days of quenching at 530 which is the solution temperature of this alloy .the hardness of 6063 alloy has a maximum value (40) after (14)days of quenching at 520 which is the solution temperature of this alloy. The hardness which is conformed to the references.

Sign in / Sign up

Export Citation Format

Share Document