Liste des documents
Microstructural and mechanical properties of WC-Co/1020 steel joints obtained by oxyacetylene and TIG brazing process
In this work, the microstructure evolution and the mechanical behavior of WC-Co / 1020 steel joint obtained by oxyacetylene and tungsten Inert Gas (TIG) brazing process are investigated. The maximum peak temperature induced by TIG process and the introduction of shielding gas causes a remarkable inter-diffusion at WC-Co/braze interface. The diffusion of Co Towards the braze in the interface obtained by TIG process is greater compared with the oxyacetylene ones. On the other side, a short range diffusion of Ni towards the WC-Co is observed. This phenomenon leads to create a new zone devoid in Co elements with high WC particle concentration at WC-Co/braze interface using TIG brazing process. The mechanical behavior is carried out through shear and micro-hardness test, they show that the presence of the new zone concentrated in WC particles beside the hard metal, makes the joint less strong than the one obtained by the oxyacetylene brazing, despite the inter-diffusion of Co and Ni elements in the interface. However, special shear test (SST) reveals that the joint made by the TIG process is resistant as much as the oxyacetylene brazing one. Voir les détails
Mots clés : WC-Co cermet, TIG brazing, Interface, inter-diffusion, mechanical behavior
Structural modification and magnetic properties enhancement with Er3+, of sol-gel TiO2 thin films
Nano-crystalline un-doped and erbium doped TiO2 thin films were dip-coated on glass substrates by sol-gel method. The films were annealed at 450 °C during 1 hour. DSC results show that the crystallization effectuates at 339°C for un-doped TiO2, whereas for erbium doped TiO2 the crystallization occurs earlier with two separated exothermic. XRD diagrams illustrate that un-doped and erbium doped TiO2 crystallize in anatase phase only and indicate that the crystallite size decreases from 24 to 21 nm as a function of the increase in Er3+ content. This result is confirmed by Raman spectra. Moreover, the VSM results indicate, on one hand, a ferromagnetic behaviour of the un-doped TiO2. On the other hand, the incorporation of Erbium leads to an enhancement of the ferromagnetic behaviour. It is worthy to mention that the weak Er3+ doping (0.1 at.%) is the high ordered magnetically with highest saturation magnetization of 1.92 memu. Both elaborated TiO2 and Er:TiO2 films show good structural properties and have a diluted magnetic semiconductors structure. The films are promising for the possible applications in optoelectronic devices. Voir les détails
Mots clés : TiO2 doped Er3+, Structural properties, sol-gel, Magnetic Properties, oxygen vacancies.
Microstructural Analysis and Mechanical Properties of Cr 13 Ni 5 Mo 2 Super Martensitic Stainless Steel
Super martensitic stainless steel Cr 13 has been widely used in many applications particularly in the oil field for their superior mechanical properties and a corrosion resistance. In the present work, we study the microstructure and mechanical properties of a super martensitic stainless steel Cr 13% Ni 5% Mo 2% after quenching treatment at 1050 °C and tempering at 700 °C for 1 hour. Chemical analyzes were obtained by X-ray fluorescence and EDS / SEM. The experiment results that microstructure after heat treatment consisted of martensite and residual austenite estimated at 29%.For mechanical analysis, several methods of investigation were used namely micro indentation, testing tensile and charpy impact test. The friction wear is investigated in dry conditions and ambient air by pin-on-disk tribometer at 2, 6 and 10N load against WC ball. The friction coefficient (COF) varied from 0.62 to 0.56 and wear rate varied from 2.4 10-3 (mm3/N.m) to 0.6 10-3 (mm3/N.m). The wear mechanism was studied by scanning electron microscopy. Voir les détails
Mots clés : Super Martensitic Stainless Steel, heat treatment, structure, mechanical properties, wear.
Eddy Current Analysis of Titanium submitted to the stress
Inspection by eddy current is one of techniquesthat are very used in nondestructive evaluation of materials. Theobject of this work is to carry out an analysis of the residualstresses in the material created by external solicitations andanalyses by eddy currents as a non destructive testing method.The analysis of the eddy current results will be compared to theresults obtained by the traditional methods (X-rays diffraction…)in order to determine a relation between the non-destructive testsand destructive. It was shown in this work that all microstructuremodifications of the samples were detected and they can bequantified by eddy current impedance measurement. Theimpedance analysis by eddy current will be correlated with themicrostructure changes observed in the material because ofplastic damage and fatigue. Voir les détails
Mots clés : NDT, Stress, Eddy Current, impedance, titanium
ÉTUDE DES PROPRIÉTÉS THERMIQUES DES BATTITURES DU LAMINOIR À CHAUD COMPLEXE SIDERURGIQUE El-HADJAR-ANNABA
Les battitures de laminoir à chaud du complexe sidérurgique d’El-Hadjar-Annaba représentent 0,1% de la production annuelle des produits plats laminés causant des pertes qui peuvent être valorisées dans certains domaines d’application.A priori, nous avons étudié les propriétés thermiques des battitures provenant du laminoir à chaud. La formation de ces battitures au cours de laminage dépend de plusieurs facteurs métallurgiques, en particulier la température dans le four de réchauffage, la pression partielle des gaz dans les différentes zones du four poussant, le temps de séjour à l’intérieur du four etc…L’analyse thermique par DSC et TGA montre des pics exothermiques synonyme d’une déshydratation et déshuilage de la calamine et des pics endothermiques indiquant une éventuelle recristallisation des oxydes de fer en l’occurrence FeO qui est stable au-delà d’une température de 570°C. Voir les détails
Mots clés : Battitures, oxydation, Laminage, Propriétés thermiques, DSC-TGA
Physical and chemical analysis of the material cast of a prosthesis for tibia (morphology and DSC).
In this approach, we have shown the results of Scanning Electron Microscope characterization (SEM), Optical Microscopy and Differential Scanning Calorimetry (DSC). The prosthesis is a composite material consisted of an organic matrix reinforced by a glass fiber and perlon, prepared by a standard casting method under vacuum. All our results show us: -The microscopic analysis has a porous structure. -Furthermore, the optical micrography chows the arrangement of the fiber in the matrix. -The result of Differential Scanning Calorimetry shows a glass transition (Tg). Voir les détails
Mots clés : physical analysis, prosthesis for tibia, MEB, DSC, optical microscopy.
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.
PROPRIETES ELECTRONIQUES DES NANOCOMPOSITES Ni/MgO
Le but de ce travail est d'étudier les propriétés électronques des nanocomposites Ni/MgO, obtenus par imprégnation avec échange ionique, suivie soit d’une irradition gamma, soit d’une calcination diverses températures (T=100-600°C). La diffraction des rayons X a révélé la formation de l’hydroxyde de magnésium après l’étape d’imprégnation. Après traitement thermique, cette phase disparait au détriment de composés intermétalliques Mg-Ni (Mg2Ni, Mg6Ni et Ni2Mg), qui à leurs tour disparraissaient audela de 300°C.L’étude ds propriétés électroniques des composites Ni/MgO par la spectroscopie (XPS), a confirmer la formation de composés intermétalliques Ni-Mg, et qui affecte l’energie de liaison de l’oxyde de nickel (NiO) détécté en surface. Voir les détails
Mots clés : Ni-MgO, nanoparticules, XPS
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
Structural and strains analyses of FeCo/A2o3 elaborated by milling time
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/Al2o3 nanostructured, MEB, DRX, EDX