Papers by Keyword: Positron Annihilation Lifetime Spectroscopy

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Authors: Emad A. Badawi, M.A. Abdel-Rahman, Alaa El-Deen A. El-Nahhas
Abstract: The aim of this work is to establish a correlation coefficient between the positron annihilation lifetime technique (PALS) and the Vickers hardness for the heat treatable aluminum alloys (6066, 6063).The potential of positron annihilation spectroscopy in the study of light alloys is illustrated with special regards to age hardening, severe plastic deformation, annealing and quenching in aluminum alloys. Vickers hardness is the standard method for measuring the hardness of metals, particularly those with extremely hard surfaces. Accordingly, a correlation coefficient of 90 % between τ and Hv is obtained. This correlation can help us to explain many behaviors of these alloys under deferent conditions.
Authors: Danny Petschke, Torsten E.M. Staab
Abstract: We follow changes in the micro structure at several distances from the weld nugget of friction stir welded AlCuLi-alloy (AA2198) plates occurring due to the tool movement and the created heat by employing different methods: Small Angle X-ray Scattering (SAXS), giving information on type, size and density of precipitates, Differential Scanning Calorimetry (DSC), giving information on formed precipitates by their dissolution signal, and positron annihilation lifetime spectroscopy (PALS), being sensitive to vacancies and dislocations as well as to the formation and growth of precipitates. We start by characterizing the base material as a reference and proceed via the heat-affected zone to the weld nugget. By the use of complementary methods, we obtain information on structure, kind and distribution of precipitates and correlate this with hardness measurements.
Authors: Alexander Stronski
Abstract: Defect configuration of Ge5As37S58 chalcogenide glasses was studied by positron annihilation lifetime spectra (PALS). Size of nanovoids was determined using Liaos formula for radius of nanovoids in spherical approximation. Peculiarities of structural features were obtained from Raman spectra.
Authors: Valerii Razov, Viacheslav Trukhin
Abstract: It is known that positron annihilation lifetime spectroscopy (PALS) maintains a strong position among the matters structure research methods. This method is based on the positron lifetime registration implanted into the test substance. One of the models describing the positron behavior in the given medium is a model of traps. Developed by Brandt, Berko and Walker in the 1960s, this model is still relevant in the present times. The basis of this model is the system of kinetic equations describing the various options of positron annihilation in the medium. The objective of the current research was to relate these equations with the parameters obtained while processing the PALS spectrum. In the given article it is presented a program for processing the time spectrum using the model traps, comparative analysis using different ways of processing and some data on the mentioned analysis respectively.
Authors: Emad A. Badawi, M.A. Abdel-Rahman, Mohammed Salah, Mohamed Abdel-Rahman
Abstract: Due to the great effect of defects on the properties of the material including strength, ductility, resistivity and opacity, there are many techniques that are used in defect detecting. Positron annihilation spectroscopy (PAS), Vickers hardness, and X-ray diffraction were used to study the influence of plastic deformation on the properties of 8006 Al-alloy in this work. An increase in the positron lifetime and Vickers hardness with a bit Broadening of XRD peaks was observed with increasing the degree of deformation reflecting a large dislocation density produced by plastic deformation.
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