Métallurgie
Infiltration behavior of Cu and Ti fillers into Ti2AlC/Ti3AlC2 compositesduring tungsten inert gas (TIG)brazing
Herein we study the infiltration behavior of Ti and Cu fillers into a Ti2AlC/Ti3AlC2MAX phase composites using aTIG-brazing process. The microstructures of the interfaces were investigated by scanning electron microscopyand energy dispersive spectrometry. When Ti2AlC/Ti3AlC2 comes into contact with molten Ti, it starts decomposinginto TiCx, a Ti-richandTi3AlC; when in contact with molten Cu, the resulting phases are Ti2Al(Cu)C, Cu(Al), AlCu2Ti and TiC. In the presence of Cu at approximately 1630 °C, a defective Ti2Al(Cu)C phase was formedhaving a P63/mmc structure. Ti3AlC2 MAX phase was completely decomposed in presence of Cu or Ti fillermaterials.The decomposition of Ti2AlC to Ti3AlC2 was observed in the heat-affected zone of the composite.Notably, no cracks were observed during TIG-brazing of Ti2AlC/Ti3AlC2 composite with Ti or Cu filler materials. Voir les détails
Mots clés : MAX phase, Joining, microstructure, hardness, Brazing, TIG process
Contribution à la diminution des criques de rives qui apparaissent dans les bramesd’acier en coulée continue.
En coulée continue, la qualité des produits et la productivité de l'installation sontfortement dépendantes du réglage du refroidissement secondaire adopté.Le problème de recherche concerne l’ACO1 (aciérie à oxygène numéro1) localiséeà Arcelor-Mittal/Annaba. Il concerne les brames présentant des défauts de criques derives.La rupture à chaud, ou crique à chaud est un défaut majeur en solidification, quiconduit au rebut de nombreuses pièces dans différents procédés industriels tels que lasolidification en lingotière, la coulée continue de brames.Les défauts les plus répandus au niveau de la coulée continue (Arcelor-Mittal -Annaba) sont les criques de rives : Elles sont petites et fines, sur les coins, longueurenviron 50 mm, profondeur 1 à 2 mm. Elles sont à cheval sur la face et sur la rive.L’élaboration d’un modèle thermomécanique permettant de prédire les profils detempérature sur les différentes faces de la brame en fonction de son passage d’unezone de refroidissement à une autre de la machine de coulée continue et notammentsur les bords.Cette étude confirme la nécessité de considérer les défauts de criques de rives vis-àvisde leur présence au niveau des brames lesquelles sont laminées à chaud ; leproduit final étant une bobine qui doit être saine. Voir les détails
Mots clés : coulée continue, acier, brames, criques de rives
Frittage de l’Hydroxyapatite HA poreuses élaborées
Au cours des dernières années, la nécessité de substituer et la réparation des tissus endommagés durs (os, articulations, dents) a augmenté en raison de maladies et les blessures.Avec la demande croissante de matériaux bioactifs pour orthopédique ainsi que la chirurgie maxillo-faciale, l'utilisation d'hydroxyapatite HA en tant que charges, les espacements et des substituts de greffe osseuse a reçu une grande attention surtout au cours des deux dernières décennies, principalement en raison de leur biocompatibilité, bioactivité et ostéoconduction en ce qui concerne les caractéristiques pour accueillir les tissus.Nous allons présenter le mode d’élaboration du d'hydroxyapatite, ensuite la densification de pastilles poreuses pour le teste de régénération. Voir les détails
Mots clés : élaboration, hydroxyapatite, frittage, porosité
Elaboration and characterization of thin solid films containing cerium
Cerium oxide films are widely studied as a promising alternative to Cr(VI) based pre-treatments for the corrosion protection of different metals and alloys. Cathodic electrodeposition of Cerium containing thin films was realised on TA6V substrates from a Ce(NO3)3,6H2O and mixed water-ethyl alcohol solutions at 0.01 M. Experimental conditions to obtain homogeneous and crack free thin films were determined. The deposited cerium quantity appears proportional to the quantity of electricity used, as indicated by the Faraday law. Subsequent thermal treatment lead to a CeO2 coating, expected to provide an increase of TA6V oxidation resistance at high temperatures. The deposits were characterized by differential scanning calorimetry (DSC), optical and scanning electron microscopies.Titanium and its alloys have been considered as one of the best engineering materials for use in industrial application due to their high specific strength, good corrosion resistance and biocompatibility [1-3].However, a major problem of titanium alloys is an insufficient wear resistance and serious oxidation at high temperature [4,5].To combat this problem, conversion coatings are widely used as part of the corrosion protection system [6]. The use of rare-earth compounds particularly cerium compounds have attracted significant attention for corrosion protection of metals and alloys as a result of new environmental regulations to replace toxic compounds [7, 8]. Cathodic electrodeposition has been used because of the low cost of equipment and of precise control of deposited thickness [9,10]. The focus of this study is on cerium based conversion coatings, wich have shown promise as potential replacements for chromates [11,12]. In the present work, an electrodeposition technique was used to get, in one step, thin cerium containing films over all surfaces of TA6V samples. The deposits were then submitted to a thermal treatment under argon in order to get a CeO2 coating, the aim being to later study the behaviour of such a coated material under high temperature oxidation conditions.The electrochemical bath was a 0.01 M Ce(NO3)3 solution, obtained by dissolving commercial cerium nitrate (Ce(NO3)3, 6H2O, 99.99% purity) in water 50 vol.% ethyl alcohol. Electrodeposition was realised using a classical three electrode experimental set-up, described elsewhere [13,14], including a TA6V sample as cathode, a platinum grid counter electrode and a saturated calomel electrode (SCE) as reference. Deposition experiments were carried out in galvanostatic mode, current density varying from j= -2 to - 0.05 mA cm-2, at ambient temperature and without stirring. Deposition time was varied from 100 to 7200 s. The variation of the potential versus time was recorded during deposition. After electrodeposition, samples were rinsed with ethyl alcohol and air dried for at least a night before further use or analysis. These experimental conditions were chosen from previous work [14] and were expected to provide thin films with a thickness in the range 50–500 nm.The aim of this work was to determine adequate parameters for cathodic electrolytic deposition, on TA6V substrate, of cerium hydroxide films from mixed water–ethyl alcohol solutions to obtain, after a thermal treatment, thin CeO2 films(<500 nm), suitable for high temperature purposes. The deposit weight and hence the deposit thickness was shown to increase with current density at a constant deposition time. However, low current densities (-0.2 mA.cm-2) promoted the formation of thin, crack-free films (which was not the case for higher current densities). The deposited cerium quantity appears proportional to the quantity of electricity used, as indicated by the Faraday law. Microscopic observations (-0.2 mA.cm-2) revealed that formed cerium hydroxide films are uniformly deposited all over the sample surfaces. The results of the DSC analysis are in perfect concordance with the literature. This study thus illustrates that electrolytic deposition can be used to obtain thin and uniform cerium films over a metallic substrate used as the cathode. High temperature oxidation experiments are currently performed on coated specimens. First results are quite promising. Voir les détails
Mots clés : electrodeposition, Cerium oxide, Cthodic deposit, Titanium alloy.
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
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.
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
Study of microscopic and thermal properties of iron-based powders obtained by high-energy ball milling of Calamine
Abstract:This study was carried out with an intention to prepare iron-based powders from metallurgy industry waste called Calamine. The latter consists of oxides scale formed on the surface of hot rolled steel. The mechanical alloying process used in this work is high-energy planetary ball mill.Morphological and thermal shifts of the milled oxides scale powders were characterized by optical microscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The results showed that the oxide scale contains more than 98% of iron. Voir les détails
Mots clés : calamine, iron-based powders, mechanical alloying scanning electron microscopy, thermal analysis
Etude de soudage TIG d’un alliage d’aluminium 2219 appliqué dans l’aérospatial
Ce travail, présente le soudage TIG de l’alliage d’aluminium A2219 très utilisé dans le domaine aérospatial comme les bacs de stockage du carburant de fusée. Il comprendra une soudure réalisée selon des paramètres de soudage optimisés suivie d’une étude macroscopique, microscopique par microscopie optique(MO) et microscopie électronique à balayage (MEB) ; ce qui nous permet d’identifier les différentes zones et d’évaluer l’évolution microstructurale de l’effet thermique dû à l’apport calorifique du soudage TIG. Des profils de micro dureté sont tracés et déterminent l’état mécanique des différentes zones. Nous constatons une baisse de dureté sur la zone fondue(ZF). Ce résultat est confirmé par une chute brutale de la résistance à la rupture et une diminution de l’allongement de la soudure. Voir les détails
Mots clés : soudage TIG; alliage d’aluminium; A 2219; soudage d’aluminium