N.A. Kamel

Defect Investigation of Plastically Deformed Al 5454 Wrought Alloy Using PADBS and Electrical Measurements

Positron Annihilation Doppler Broadening Spectroscopy (PADPS) is a nondestructive technique used in materials science. Electrical measurements are one of the oldest techniques also used in materials science. This paper aims to discuss the availability of using both PADPS and electrical measurements as diagnostic techniques to detect defects in a set of plastically deformed 5454 wrought aluminum alloys. The results of the positron annihilation measurements and the electrical measurements were analyzed in terms of the two-state trapping model. This model can be used to investigate both the defect and dislocation densities of the samples under investigation. Results obtained by both nuclear and electrical techniques have been reported.

Determination of the Activation Energy for Formation and Migration of Thermal Vacancies in 2024 Aircraft Material Using Different Techniques and Methods

Positron annihilation lifetime (PAL) , electrical and mechanical techniques have been used to study the thermal vacancies in one of the most important engineering aluminum alloys which is 2024 alloy. Quenching experiments were usually performed on thin specimens to ensure a uniform quenching rate throughout the specimen. The specimens were prepared with dimensions of 0.15 × 1.5 × 1.5cm3. After grinding, polishing and etching, samples of 2024 were homogenized for 12 h at 673 K and annealed for 90-min., before quenched in water (277 K) and then subject to positron lifetime, electrical and mechanical for measurements. From such measurements it is possible to deduce the vacancy formation enthalpy, which in combination with the results of self-diffusion measurements, give a value for migration enthalpy of the vacancy. These are very important quantities in the study of the annealing of irradiation induced defects.

Determination of the Activation Energy for Formation and Migration of Thermal Vacancies in 401.0 Casting Aluminum Alloy

Electrical techniques have been used to study the thermal vacancies in 401.0 casting aluminum alloy. Quenching experiments were usually performed on thin specimens to ensure a uniform quenching rate throughout the specimen. After grinding, polishing and etching, samples of 401.0 were homogenized for 12h at 673K and annealed for 90min., before quenched in water (277K) and then subjected to electrical measurements. From such measurements it is possible to deduce the vacancy formation enthalpy, which in combination with the results of self-diffusion measurements, give a value for the migration enthalpy of the vacancy.

A Study of the Effect of Natural Aging on Some Plastically Deformed Aluminum Alloys Using Two Different Techniques

Electrical and mechanical techniques have been performed in order to study the effect of natural aging for up to more than 650 days on wrought (2024, 7075) and cast (AlSi11.35Mg0.23, AlSi10.9Mg0.17Sr0.06) aluminum alloys, after having been deformed at room temperature to 25% deformation. The results revealed that, unlike dislocations, point defects were removed from the samples under investigation except for 7075 alloy and this can be attributed to no point defect introduced in this particular sample during the deformation.

Study of Production Defects in Pure Aluminum and 3003 Aluminum Alloy by Electrical Measurements

To Study the Defect Properties in the Crystal, it Is Necessary that they Are Present in Sufficiently High Concentration. Electrical Measurements Are Also One of the Oldest Techniques Used in Materials Science. this Paper Aims to Discuss the Possibility of Using Electrical Measurements as Diagnostic Techniques for Detecting Defects in a Set of Plastically Deformed Pure and 3003 Al Wrought Aluminum Alloys. the Results of Electrical Measurements Were Analyzed in Terms of the Variation of Resistivity. this Model Can Be Used to Investigate both the Defect and Dislocation Densities of the Samples under Investigation. Results Obtained by Means of Electrical Techniques Have Been Reported. Plastic Deformation Was Performed, and I-V Curves Were Measured in Order to Determine the Value of the Resistivity. the Values of Resistivity as a Function of Deformation and Annealing Behavior Were Studied. One of the Goals of the Work Was to Obtain the Activation Energy for the Formation of Defects by Performing Electrical Measurements on both Materials (pure Al and 3003 Al Alloys ).

Correlation between Nuclear and Electrical Methods for Estimating the Activation Enthalpy of Defect Formation in 2024 Alloys

The Objective of this Research Was to Investigate the Use of a Sensor System to Monitor Continuously the Defect Formation Response of Heat-Treatable Aluminum Alloys. the System Continuously Monitors a Material Property, Resistivity, which Is Indicative of the Quenching Process. such Studies Will Allow us to Gain Active Control of the Aging Process and Hence the Material Properties of Aluminum Alloys.

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

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.

Isochronal and Isothermal Annealing of Wrought Aluminum Alloy

Positron annihilation lifetime (PAL) is one of the most important nuclear techniques used in material science. Electrical measurements are also used in material science. Samples of 25 % deformation have been used for these studies. Both positron annihilation lifetime and electrical measurements were used to determined the activation energy of migration the dislocation in 7075 alloy. The isothermal annealing measurements were performed at 643, 663, 683 and 703 K. The activation energy of migration the dislocation are obtained as 1.35 ± 0.16 eV and 1.25 ± 0.05 eV for positron annihilation lifetime and electrical techniques respectively.

Effect of Ageing on Microstructures, Electrical Properties and PALS of Aircraft Al Alloy 2024

A comprehensive and systematic study using PALS technique, Vickers hardness test and electrical LCR meter were undertaken to follow property development during the recently promoted interrupted ageing treatment for 2024 aluminum alloy. In this work, solution heat treatments at different temperatures were performed in aircraft materials 2024 aluminum alloy. This work describes the development of the dependence of mechanical, electrical properties of 2024 Al-alloys on heat treatment to characterize microstructural changes during heat treatment. PALS, mechanical and electrical testing will be used to measure the features of the material as a function of time for each ageing temperatures.

Dislocation Recovery in Casting Alloy by Positron Lifetime Technique

Recovery behavior of 20% plastically deformation of casting AlSi11.35Mg0.23 in various stages of isochronal annealing has been investigated by positron Lifetime (LT). The experimental results show that the positron mean lifetime is a function of annealing temperature. Lifetime of the positron annihilating in perfect lattice is 187.3ps and in 20% deformed is 229.8 ps. There are two regions in the isochronal annealing, one of them relating to the point defect and the other to the dislocation. The activation enthalpy for the dislocation is calculated from the isothermal study in the dislocation region from (575-675) K by slow and fast cooling as 0.16±0.02 and 0.53±0.06 eV respectively.