Sciences des matériaux
PREPARATION OF ELABORATION AND CHARACTERIZATION OF CdZnS THIN FILMS DEPOSED BY CHEMICAL BATH DEPOSITION
This work involves the development of thin films of CdxZn1-xS on glass substrates for photovoltaic applications, solar cells. The thin buffer CdZnS was synthesized by chemical bath (CBD), with different deposition protocols, studies the parameters influencing these layers as the temperature, deposition time and pH. The structural and optical properties of various thin films are studied and in relation to the photovoltaic performance. This work is a contribution in the field of thin films, to revive the CdZnS a new air of research and its introduction to nanotechnology. The different structural, morphological and optical analyzes yielded very interesting results. Voir les détails
Mots clés : CdZnS, chemical bath, Thin films, solar cells.
Structural and strains analyses of FeCo/A2o3 elaborated by mechanical milling
The effect of milling time of Fe matrix strengthened with 40% wt % Al2o3 during mechanical alloying was examined for nanocomposite alloy at different milling times (5, 15, 20, 30 h), during milling the lattice strain increased from 0.34 to 0.64%, and residual stress increased from 93.024 to 175.104 Gpa, it is due to sever deformation plastic. Voir les détails
Mots clés : Fe/40Al2o3 nonocomposite, MEB, DRX, EDX
Elaboration and characterization of a piezoelectric ceramic resonator
In this work. We Synthesized PbTiO3 from PbO and TiO2 oxides from Solid state reaction and we studied the development and manufacture of solid piezoelctrique resonator of PT .We played on parameter as sintering time. We used XRD and SEM for morphological characterization and Analyzer for impedance piezoelectric characterization. Voir les détails
Mots clés : PT, ferroelectric, resonator, impedance, XRD, SEM
INFLUENCE OF ALLOYING ELEMENTS OF WELD METAL ON MECHANICAL BEHAVIOR OF HSLA-X70 WELDS
In the pipeline industry, the alloying elements are continually evolving as a function of weldability and reliability of steels. For this reason, metallurgists discover and develop every day new base materials like HSLA steels and efficient electrodes. We propose in this work to study the influence of chromium and molybdenum in C-Mn filler metal, hoping to demonstrate their microsturctural evolution and mechanical behavior on welds of high strength steels HSLA-X70. The mechanical properties included hardness, impact and tensile strength was investigated. The results show that, optimal properties of welds correspond to the existence of both molybdenum and chromium in weld metal with proportions varying between 1% and 2.5%. Voir les détails
Mots clés : alloying element, Weld metal, HSLA-X70, TIG welding, mechanical behavior
Experimental study of metal transfer of CMT welding
The CMT welding process was investigated in this work. The transfer of Al-4043 filler metal during welding was visualized using a high-speed camera with a green laser as an illumination source. Three phases was identified during the transfer cycle. A hot phase during which a molten droplet is formed on the end of the wire electrode under a high current. A cold phase corresponds to the move of the wire toward the weld pool. The contact between the droplet and the weld pool create a short circuit during which the material transfer is initiated and the arcing current reduced. After a set time (in the middle of the short circuit phase), the wire is retracted mechanically to contribute to the droplet detachment without increasing in current welding. The effect of the current waveform on the metal transfer is investigated too. The reduction in the hot phase duration of the current waveform decreases the volume of liquid droplets at the wire tip and allows to increase the short-circuit frequency. Voir les détails
Mots clés : CMT welding; waveform; current; transfer; phase; droplet
Effect of resistance spot welding parameterson mechancial behavior of thin sheet
Different welding methods have been developedfor joining stainless steels; however, resistance spot welding is thepromising method for welding of thin sheets of these steels.Resistance spot welding is a non-solder process that uses thecombined effect of mechanical pressure and an electric currentpassing through the parts. In this study, commercially 304Lstainless steel sheets were welded by resistance spot welding atvarious welding parameters (welding effort, welding times andintensity of current welding. The results showed that theparameters, effort and welding time have little effect onmechanical properties compared with respect to the effect of theintensity of the current welding. The experimental results showalso that the welding current is an important parameter forjoining structures and its mechanical strength. The hardness andexternal aspects of spot were carried out in order to examine theinfluence of welding parameters on the welded joints. Hardnessmeasurement results indicated that welding nugget had thehighest hardness and this was followed by the heat-affected zoneand the base metal. Voir les détails
Mots clés : resistance spot welding, hardness, mechanical strength, stainless steel, electric current, welding time
Impact of the heat treatments on the microstructure of the aluminum alloys 7075 T6 welded by the friction stir welding process
The welding process of the aluminum alloys 7075 T6 is increasingly used in the aeronautical industry. The use of the friction stir welding process (FSW) requires a good understanding of the microstructure generated by the rapid temperature rise in the heat affected zone and the thermomechanically affected zone of the used alloy. By applying the process of welding FSW, the characterization of the microstructure, because of the diversity of its components in terms of size and nature, requires the use of multiple techniques of investigations such as the use of optical microscopy and scanning electron microscopy for local approaches. It also requires the use of the impact strength test to assess the quality of the weld, to characterize the interaction between the material and the welding process, and to provide quantitative data on the welded joints behavior. Voir les détails
Mots clés : Aluminum alloys 7075 T6, Friction stir welding process (FSW), heat treatment, microstructure, Impact strength test.
Comparaison entre le soudage FSW et le soudageBout a Bout pour le polyéthylène à haute densité(PEHD)
L'objectif de cette étude est la maîtrise de la technique duSoudage par Friction Malaxage (Friction Stir Welding - FSW) etloptimisation des paramètres sur un polyéthylène à haute densité(PEHD). Ce procédé d'assemblage est basé sur le phénomène demalaxage provoqué par le passage de l'outil (pion), élémentessentiel de cette technique. Létude consistera à : 1. Réaliser dessoudures par le procédé FSW. 2. Étudier le comportementmécanique à la rupture des joints soudés. Afin de maîtriser etoptimiser le procédé en maitrisant la vitesse de rotation, lavanceet la plongée de l'outil.3. Réaliser des soudages bout à bout etfaire une comparaison entre les deux soudages Voir les détails
Mots clés : comparaison, soudage, FSW, bout a bout, PEHD
SEM/ DRX / EBSD charaterization of electricsubmerged arc welded of an industrial mow carbonsteel
In this study, we tried to understand the impact ofevolution of thermal deformation during the electric submergedarc welding process used to assembling parts. This weldingprocess is applied on an industrial low carbon steel of %C 0.19Wt, %Si 0.25 Wt, %Mn 0.40 Wt, %P 0.025 Wt, %S 0.015 Wt, %Al 0.09 Wt, %Mo 0.009 Wt, %Nb 0.05 Wt and % Ti 0.03 Wt.The plates with thickness of 2.6 mm, it is called BS2. And used bythe company SNS BAG destined for making gas storagecylinders.To highlight the present work, different areas of our specimenswere investigated especially fusion zone and heat affected zone.Characterizations performed are SEM, DRX and EBSD andshow the appearance and texture development during the weldprocess. Note that in this working part, the behavior of thermal Voir les détails
Mots clés : Low Carbon Steel, Electric arc welding, mechanical parameters, textural character formatting
Determination ofresidual stressby X-ray diffractionin a weld cordon
In this study, the implementation of the method fordetermining residual stresses by X-ray diffraction andapply it to the case of a bead of solder. Weldingprocesses induce changes in the microstructure andresidual deformations and stresses that it is so difficultto control that important To study this phenomenonof welding two pieces and low alloy low carbon, werewelded to the electrical arc with coated electrode ofmild steel. The morphology of the samples wascharacterized by optical and electron microscopy,showing the significant change in the microstructurein the different area of the cord. The hardness profilesobtained show that the hardness is stable (200 Hv) inthe base metal and increases in the cord (230 Hv). Inthis work, the X-ray diffraction was used to analyzethe residual stresses. The results of measurements onthe crude sample show that the constraints are allcompression, with a higher level in the side region tothe cord and in the base metal. The relief annealed at650 ° C relaxes the constraints to a lower level whileremaining compressive. These results show that thepresent solder interesting mechanical and structuralcharacteristics, having regard to the present ofresidual compressive stresses, the absence ofstructural defects and cracks. Which promotes goodperformance and long life of the part in its operation. Voir les détails
Mots clés : soudage, contraintes résiduelles, diffraction de rayon X, microscopie.