Papers by Author: M.Y. Debili

Abstract: Structural characteristics and thermal behavior of the conventionally solidified Al₈₀Cu₁₄Fe₆, was investigated by X-ray diffraction, optical microscopy, and differential thermal analysis techniques. It was found that the formation of quasi crystalline phase occurs after annealing for relatively low temperature (500°C) during a short time.

Abstract: This work deals with Al-Cu thin films, deposited onto glass substrates by RF (13.56MHz) magnetron sputtering, and annealed at 773K. The film thickness was approximately the same 3-4µm. They are characterized with respect to microstructure, grain size, microstrain, dislocation density and resistivity versus copper content. Al (Cu) deposits containing 1.8, 7.21, 86.17 and 92.5at%Cu have been investigated. The use of X-ray diffraction analysis and transmission electron microscopy lead to the characterization of different structural features of films deposited at room temperature (< 400K) and after annealing (773K). The resistivity of the films was measured using the four-point probe method. The microstrain profile obtained from XRD thanks to the Williamson-Hall method shows an increase with increasing copper content.

Abstract: It is the intention of this paper to present the results of a study of Al-Fe-Ti (26-50Fe-2wt%Ti) cast alloys. We have examined the solidification structure over a wide range of iron contents. Using X-ray diffraction and quantitative microstructural analysis, we have characterized the alloy microstructure and identified second-phase crystallographic structures. The hardness of the alloys was also determined. The solidification structure was modified by the addition of Ti to Al1-xFex alloys.

Abstract: Rapidly solidified Al-Zn alloys with Zn contents ranging up to 50 wt.% were made under vacuum, by high-frequency (HF) induction melting, from compacted mixture targets of Al and Zn of fine (99.99 % purity) elemental powders. The microstructural characteristics and strengthening mechanisms were investigated. The crystallographic microstructures were characterized by means of X-ray diffraction (XRD) analyses and optical microscopy observations as well as Vickers microhardness testing. Detailed overviews of alloying solubility of zinc in aluminium were given. Extensive solid solutions of CFC Al were found in the (HF) Al-Zn alloys, and a higher Vickers microhardnesses compared to that of pure (HF) aluminium.

Abstract: In this work we are interested by the decomposition behaviour after heat treatment at 500°C of nanostructured Al-Cu deposits, prepared by radio frequency (13.56MHz) magnetron sputtered from composite targets. The use of X-ray diffraction leads to the characterization of different structures and the estimation of grain size and dislocation density. The grain size of the films is found to increase with annealing. The dislocation density is observed to exhibit a decrease trend with annealing temperature which leads to a reduction in the concentration of lattice imperfections A specific thermal study of the Al-Cu deposits, by combined thermal analysis (TDA/TG) permit to follow the structural behavior of the deposits with heat treatment. For Al-7.21at%Cu deposit, the exothermic peak convolution may be due to the elimination of micro deformations present in the sample.

Abstract: X-ray tools are being powerful methods for qualitative and quantitative analyses of nanocrystalline materials This work is an overview of detailed X-ray investigations relative to microstructural studies applied for a refined binary Al-based alloys thin films system as samples deposited on glass substrates. Energy dispersive analysis of X-ray (EDAX), X-ray diffraction (XRD) and transmission electron microscopy (TEM) methods were used to determine the chemical composition, the microstructure parameters and the solubility of copper in aluminum.

Abstract: The instrumented indentation technique is being widely used for the determination of elasto-plastic properties of metallic materials by analyzing located atomic force microscopy (AFM) image area and loading-displacement data of indentation imprints after testing. This data analysis is highly dependent on the method followed for interpretation the loading and unloading curves. We have detailed the two common methods, the Oliver&Pharr method based on a power law and the energetic approach method based on finite elements, in order of understanding the nano-indentation unloading behavior to determine the closer hardness and Young’s modulus of metallic materials..

Abstract: The thermomechanical treatment at 1050°C under a stress of about 30 MPa, of milled ribbons from Fe-25Cr-20Ni (0.060%Ni-0.1%Ti) refractory stainless steel, leads to a recrystallisation of the as-melt-spun structure which is intermediate between cellular and columnar dendritic. The mean grain size in the relatively high density zones (85%) may be considered as low and do not exceed 10µm. Other grains appear abnormally large and reach 30µm. The origin of these grains, must be researched in an exaggerate growth phenomenon under a local deformation near the critical work hardening.