Papers by Author: Rachid Halimi

Abstract: X-ray microanalysis was used in the qualitative and quantitative study of titanium carbides obtained by deposition of thin titanium films on steel substrates using reactive r. f. sputtering of a pure titanium target. The samples are subjected to high vacuum annealing at a temperatures between 200 and 1000°C for 60 min. The morphological analysis by SEM shows that all films exhibited a dense microstructure. The EDS pattern of X-ray microanalysis shows that the non treated samples mainly consist of titanium. The concentration of Ti decreases progressively with the annealing temperature therefore the carbon and iron concentrations increases, this is as result of atomic interdiffusion between the substrate and the thin film. In the highest temperatures of annealing we note the diffusion of the elements of substrate towards outside layers even for those having weak concentrations. The relationship between mechanical properties and the reaction is carried out by Vickers micro-hardness measurements.

Abstract: Titanium carbides are well known materials with great scientific and technological interest. The applications of these materials take advantage of the fact that they are very hard, refractory and that they have metallic properties. In this work, we have studied the influence of the heat treatment temperatures (400-1000°C) on the interaction between the titanium thin films and steel substrates. Steel substrates, 100C6 type (AFNOR norms) containing approximately 1 wt % of carbon were coated at 200°C with titanium thin films by magnetron sputtering. The samples were characterized by X-ray diffraction (XRD) and Auger electron spectroscopy (AES). Vikers micro-hardness measurements carried out on the annealed samples showed that the micro-hardness increases with annealing temperature, reaches a maximum (3500 kg/mm2), then decreases progressively. The growth of micro-hardness is due to the diffusion of the carbon, and to the formation of titanium carbide. However, the decrease of micro-hardness is associated with the diffusion of iron and the formation of iron oxide (Fe2O3). At higher temperatures, we note the formation of titanium dioxide (TiO2).

Abstract: Sandwich plates, made of two aluminum layers and a metal honey comb core are used in the aircraft industry. The purpose of this study is to show the ultrasonic guided waves sensibility to discover delamination in skin-honeycomb sandwich structures used in aeronautics. Separation between the skin and the core can appear during the manufacture or after use. In this work, Lamb's waves are used to control this kind of plane structure. Indeed, these waves have the advantage to put in vibration the totality of the plate that we want to control and they propagate on long distances without too much attenuation. The revealing, by the guided waves, of the unsticking which can meet on such sandwiches, between the plate and the honeycomb core is studied and commented.