Sciences des matériaux

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Structural and tribological behavior of AISI L6 tool stee

Oualid GHELLOUDJ, Amel GHARBI, Djamel Zelmati, Sihem ACHOURI, Mounira Bourebia, Chems Eddine RAMOUL  (2018)
Article de conférence

Tool steels constitute a family of carbon steels and alloy steels that are characterized by good wear resistance. These steels are destined for manufacture of tools used for forming, cutting and machining operations of metals and alloys. Among these steels, AISI L6 Tool steel alloy with nickel, chromium, molybdenum and vanadium for hot work, it is used in applications of punches, trim dies, blanking dies, embossing dies, forming dies, and shear blades. The aim of this work is to study the tribological behavior of AISI L6 steel before and after a hardening treatment at 780 °C. Structural characterization and tribological behavior of steel were investigated using Optical Microscopy (OM) and wear testing by friction on a Ball/Pin-on-disc Tribometer. The results obtained show a decrease in coefficient of friction due to improvement of wear resistance of AISI L6 steel by hardening treatment. This improvement is favored by precipitation of very hard particles offering a better resistance to displacement of dislocations. Voir les détails

Mots clés : tribology, wear, heat treatment, hardening, structure, AISI L6

Caractérisation des couches mincespar les techniques optiques.

A. Boughelout, A. Hammouda, L. CHABANE, N. ZEBBAR et M. KECHOUANE.  (2014)
Article de conférence

Dans ce travail nous avons utilisé des techniquesoptiques et structurales pour caractériser des couches minces deZnO déposées par pulvérisation cathodique sur des substrats deverre corning et silicium monocristallin. Nous avons utilisé laspectroscopie Raman pour analyser le type de la structure descouches mince (ZnO) élaborées ainsi que la diffraction des rayonsX.Les caractérisations optiques comportent le relevé destransmittances dans l’UV-Visible et les paramètres optiques telque les indices de réfraction des couches et leurs épaisseurs, lesmesures de la photoluminescence pour déduire le gap des coucheset les niveaux des défauts dans le matériau.Les caractérisations structurales (diffraction des rayons X etRaman) mettent en évidence une structure hexagonale würtzitede ZnO, Les mesures de transmission optique des couchesmontrent que la transmission optique est très élevée (facteur detransmission) dans la gamme de longueurs d’ondes situées entre 400nm et 2500 nm. Voir les détails

Mots clés : pulvérisation réactive, oxyde de zinc, propriétés optiques, caractérisation structurale, conductivité électrique.

Rhodamine (B) photocatalysis under solar light on high crystallineZnO films grown by home-made DC sputtering.

A. Boughelout, N. ZEBBAR, R. MACALUSO, Z. Zohour, A. Bensouilah, A. Zaffora, M.S. Aida, M. Kechouane, M. Trari.  (2018)

ZnO thin films were deposited by home-made DC sputtering of zinc target under mixed gases(Argon, Oxygen) plasma on glass substrates. Films were deposited by varying oxygen partialpressure (PO2) from 0.09 to 1.3 mbar in the deposition chamber, at a fixed substrate temperatureof 100 °C. The samples were characterized by photoluminescence (PL), X-ray diffraction (XRD),optical transmissions (UV–vis), scanning electron microscopy (SEM) and electrical (Hall effect)measurements. The results indicate that by varying the oxygen pressure in the depositionchamber, the films show a precise and well defined photoluminescence emissions for each rangeof pressure covering almost the entire visible domain (UV, UV-Violet, Violet, Blue, and Red) withhigh intensities. Moreover, the deposited films have different defects levels. The XRD analysisindicates that the films are well grown along the c-axis peak, but with different crystallinequality. Optical measurements reveal a high transmission, up to 90%, in the spectral regionbetween 400 and 2500 nm and a large variation of the optical band gap (3.16 – 4.34 eV). As anapplication of the deposited ZnO films, the photo-catalytic degradation of a synthetic solution ofRhodamine B (RhB) poured on a ZnO thin film was successfully achieved and an elimination rateof 38% was obtained after exposing the film to solar light for 3 h. Voir les détails

Mots clés : ZnO thin films, sputtering, Photoluminescence, Rhodamine (B), Solar light, Photocatalysis.

Dissimilar Welding between 2205 Duplex Stainless Steel and API X52High Strength Low Alloy Steel

B. BELKESSA, D. Miroud, B. Cheniti, N. OUALI, M. Hakem, M. Djama  (2018)

This work purposes to investigate the microstructure and the mechanical behavior ofdissimilar metals weld between 2205 duplex stainless steel (UNS 31803) and high strength lowalloy steel API X52. The joining was produced by shielded metal arc welding process using twodifferent filler metals, the duplex E2209 and austenitic E309 grade.The microstructures of the dissimilar welded joints have been investigated by optical microscopy,scanning electron microscopy and energy-dispersive spectroscopy (EDS). The EDS analysisperformed at the API X52/weld metal interface showed an evident gradient of Cr and Ni betweenfusion and type II boundaries, where the highest hardness value was recorded. Voir les détails

Mots clés : Dissimilar metals welding; 2205 duplex stainless steel; API X52 HSLA steel; Heataffected zone

Evolution of Widmandstaïtten structure in welding joints

M. Hakem, R. RABAH OTMANI  (2005)

The operation of welding induces a metallurgical multitude of phenomenon owing to the fact that it covers high fields' energetic thus causing important variations of the mechanical properties and microstructural of materials. The multipass welding of a HSLA steel strong thickness gives place to a variation of the microstructure of a layer to another. The thermal cycle supports the appearance of a known structure under the name of "structure of widmanstätten". The latter is supported by high heating temperatures and a fast cooling; it often germinates in the form of slat on the austenitic grain boundaries, known like ferrite of widmanstätten. But it can germinate in the form of needles in the grains on the impurities or on the precipitates, it is acicular ferrite. Impact strength and hardness tests were done on the melted zone after welding and heat treatment.The microstructural evolution of each layer influences the entire welded joint, conferring these final mechanical properties to him. Voir les détails

Mots clés : heat treatment, HSLA steels, welding, Widmanstätten structure

Effect of microstructure and precipitation phenomena on the mechanical behavior of AA6061-T6 aluminum alloy weld.

M. Hakem, S. Lebaili, S. Mathieu, D. Miroud, A. LEBAILI, B. Cheniti  (2019)

In the present study, the effect of microstructure and precipitation phenomena on the micro hardness, tensile strength, impacttoughness, and electrochemical behavior of tungsten inert gas (TIG)-welded AA6061-T6 aluminum alloy are investigated. Themicrostructure features showed mainly the grains of aluminum solid solution with the presence of some precipitates at the grainboundaries. Scanning electron microscope micrographs exhibited the presence of Fe-based intermetallic and B-equilibriumprecipitates throughout a-Al grains. In the heat-affected zone (HAZ), the dissolution, over-aged, and coalescence of precipitatesare observed; their hardening effects disappear and a decrease in strength and hardness are noticed. The fracture toughness valuesof each zone at different temperatures using Charpy V-notch test remained constant where the HAZ presents the highest absorbedenergy. However, the temperature did not have a significant effect on the absorbed energy for each zone. In addition, the fracturedsurface of base metal (BM) and HAZ are characterized by dimple-like structure and they are larger in the HAZ. The electrochemicalbehavior of each zone of the weld evaluated in NaCl + H2O2 solution revealed that the corrosion current density of BMand HAZ is lower than that of molten zone (MZ), which displays high corrosion current density in this electrolyte and would befastest to corrode. Voir les détails

Mots clés : Aluminum alloys, TIG welding, precipitates, microstructure, Fractography, Electrochemical behavior

Natural extract of Opuntia ficus indica as green inhibitor for corrosion ofXC52 steel in 1M H3PO4

Amel Oulabbas, Abd errahmane Sihem  (2019)

The purpose of this study is to evaluate the anti-corrosive effect of natural extract of Opuntia Ficus Indica (O.F.I) for XC52steel in 1M H3PO4. Experimental work has been achieved by weight loss, potentiodynamic polarization and EISmeasurement, as well as SEM surface characterization. Among the results obtained, we can mention an inhibitory efficiencyof 90% by gravimetric method and 83.9% by electrochemical method at 10% (v/v) of O.F.I. Moreover, The O.F.I extract actsas a mixed inhibitor; however, adsorption free enthalpy indicates a physisorption. The adsorption obeys the Langmuirisotherm model. These results have been improved by SEM micrographs Voir les détails

Mots clés : corrosion, Opuntia ficus indica, EIS, green inhibitor, XC52 steel


Article de conférence

Fiber reinforced composite materials have been increasingly used as structural material in airplanes, because of their high specific stiffness and strength. Structural design and non destructive test techniques have evolved as increased emphasis has been placed on the durability and damage tolerance of these materials. This work presents the results of the damage kinetic of carbon fiber reinforced polymer using the acoustic emission under solicitations. The correlations between acoustic emission parameters and damage mechanism are identified, and then confirmed by microscopic observations. This review will emphasize the roles that AE can play as a tool for the composite materials, damage mechanisms, and characterization of damage evolution with increasing time or stress, the localization and origin of damage, quantification of crack size based on energy release from concrete structures in the field and reduction in the numbers of test specimens required in various studies. Voir les détails

Mots clés : Composite material, damage, Correlation, mechanism, localization

The corrosion resistance ofsupermartensitic steels compared to martensitic steels in different corrosion media

A.Oulabbas S. Tlili, C.E. RAMOUL, S. Meddah, F. Sehab  (2017)
Article de conférence

The supermartensitic stainless steels deduced from the refinement of the compositionof martensitic steels, have a low carbon content with 13% of chromium, 5% of nickel and 2%of molybdenum, this new generation of steel has an improved ductility with a good resistancemechanical and excellent resistance to corrosion. In this work, a comparative study of thecorrosion behavior of these two stainless steels in different aggressive chlorinated andsulphurized media was carried out. Stationary (polarization curves) and transient(electrochemical impedance) electrochemical methods have been applied. The rate ofcorrosion as a function of time was determined by the mass loss method and thecharacterization of the surface condition was studied by optical microscopy. Two types ofcorrosion were observed: uniform corrosion in which the half-reactions are homogeneouslydistributed in 0.5M H2SO4, followed by localized corrosion observed in 0.5M NaCl for bothsteels. According to the polarization curves, the corrosion potential differs betweenmartensitic steel and supermartensitic steel where it has a higher potential with -0.342 V / Ag/ AgCl in 0.5M H2SO4 and -0.339 V / Ag / AgCl in 0.5M NaCl. In parallel, the polarizationresistance given by EIS shows that in both media, supermartensitic steel is more resistant thanmartensitic steel where it has an Rp equal to 7200 Ohm in 0.5M H2SO4 and 8340 Ohm 0.5MNaCl. These results are confirmed by the optical microscope microstructure. Voir les détails

Mots clés : corrosion, martensitique stainless steel, supermartensitique stainless steel

L’Etude du comportement à la corrosiondes aciers inoxydables supermartensitiques et martensitiques dans deux milieux corrosifs

A. Oulabbas, S.Tlili, C.E. RAMOUL, S.Meddah  (2018)
Article de conférence

l'objectif de notre travail est d'étudier la résistance que les aciers inoxydable martensitique et supermartensitique présentent lors d'une attaque à la corrosion chimique. pour cela deux milieux d'attaque le premier chloruré et le second sulfaté, sont utilisés comme électrolytes. la premiere approche éttant la technique de perte de masse suivit par l'étude du comportement électrochimique ( courbe de polarisation et impédance) d'aprés les courbes de polarisations , le potentiel de corrosion différe entre l'acier martensitique et supermartensitique, ou ce dernier présente un potentiel plus noble et cela dans les deux milieux. Voir les détails

Mots clés : acier martensitique, acier supermartensitique, impédance, corrosion