Sciences des matériaux
X-Ray Diffraction Evaluation of Dislocation Density and Crystallite Size in the HAZ
The aim of this work is to study the effect of successive welding process on microstructure and mechanical properties of the heat affected zone (HAZ) in welded HSLA steel, employed in petroleum and gas transport. The analysis of the diffraction pattern profiles by the Rietveld refinement method (X-ray Diffraction Line Profile Analysis XRDLPA), allows obtaining detailed information on the evolution of the microstructural parameters such as the sizes of the domains consistent with diffraction (crystallite size), micro-deformations and dislocation densities. Based on the X-ray diffraction analysis (XRD) using Material Analysis Using Diffraction (MAUD) software, the results show an outstanding evolution of microstructural parameters in the HAZ, which means an increase in the crystallite size and a decrease in the dislocation density according to the number of welding process. Voir les détails
Mots clés : HSLA, XRD, dislocation density, HAZ.
Proposition of a mechanical model to predict the behaviour of a laminate bio composite material
The purpose of this paper is to develop a mechanical model able to predict the mechanical behaviour of a laminate bio-composite material reinforced by the flax fibres without necessity to the expensive experimental test. A numerical comparative modelling based on finite element method is conducted by using in one hand a several stacking sequences, and in the other hand a growing plies number in order to estimate the lateral deflexion U3 in each plies of the bio-composite subjected to compression load. Meanwhile, the proposed mathematical model can be used as a power tool decision in design and the ensuring of the structure integrity. Voir les détails
Mots clés : Bio-composite, laminate, flax, modeling
DEVELOPMENT AND CHARACTERIZATION OF HYDROXYAPATITE FOR BONE USE
The objective of this work is the elaboration of a biomaterial Hydroxyapatite (Ca10 (PO4)6 (OH)2), by a synthetic method of precipitation, (CaCl2, 2H2O) as source of calcium and (Na2HPO4, 12 H2O) as a source of phosphate. After preparation, the powder was calcined at 900 °C for 90 minutes at a speed of 10 °C / min and compacted into pellets 12 mm in diameter and 2 mm thick. Sintered powder at different temperatures (1000 °C, 1100 °C, 1200 °C, and 1300 °C). In order to study the effect of sintering temperature on the microstructure, the physical and morphological properties of the elaborated hydroxyapatite, the density, the porosity, X-ray diffraction (DRX) and the scanning electron microscopy (SEM) were used for the characterization of the powder. The density decreases with the increase of the porosity, in fact the sample densifies easily when the porosity is lower Voir les détails
Mots clés : hydroxyapatite, SEM, DRX, Porosity, Density
Puzzle of c-WN phase stabilization
In this paper, we present first-principles calculationsthat compare structural and electronic properties of WN inthe NaCl and NbO phases. Our results predict that the NbOstructure of WN is more stable than the NaCl structure withoutdefects, where the enthalpy of formation per formula unit Hf =-0.872eV and 0.616eV for NbO and NaCl structures, respectively.Moreover, the calculated lattice parameters of c-WN are a=4.35A°and a=4.11A° for NaCl and NbO phases, respectively. It is veryclear that the lattice parameter obtained for c-WN in NbO is invery good concordance with that reported experimentally of a =4.14A° . Although the formation energy calculations support thehypothesis of the stability of the NbO phase, the experimental xrayphotoelectron spectroscopy (XPS) electron density of statesfor valence band spectra corresponds to that density of statescalculated for c-WN in NaCl phase. Based on this comparison,more consideration must be taken into account to elucidate thisissue. Voir les détails
Mots clés : Cubic Tungsten nitride ceramics, Firstprinciples calculations, Formation energy
Experimental study of the thermo-mechanical behaviour of alumina-silicaterefractory materials elaborated from Algerian kaolinitic clays
This work aims to study the thermomechanical behavior of an algerian kaolinitic clay. We started with the characterization of the raw material (DD1) of Djebel Debbagh -Guelma, in order to obtain a deep information about the microstructure of the material before and after a heat treatment, notably its crystallographic nature and the grains size and shape. The chemical composition and physical properties are reported. The mineralogical and chemical characteristics, based on X-ray diffraction (XRD) and scanning electron microscopy (SEM), were also carried out. The general behavior of the material with increasing temperature was analyzed through the various microstructure investigations and thermal analysis. Voir les détails
Mots clés : Thermo-mechanical properties, aolinitic clays, elaborate
Approche expérimentale des causes d’endommagement des marteaux de concassage
Les matériaux résistant à l’usure sont fortement demandés par divers secteurs industriels (industries minières, métallurgiques et autres). Ils constituent des pièces maîtresses des concasseurs et des broyeurs utilisés pour la préparation des matières. Plusieurs nuances d’aciers sont produites pour répondre aux besoins de divers secteurs industriels. D’autres aciers martensitiques à haute teneur en carbone et en chrome sont aussi produits pour répondre à des sollicitations nécessitant une résistance à l’usure élevée.Dans ce travail nous nous intéressons aux causes de dégradation prématurée des marteaux de concassage. Ces marteaux, à leur entrée en service, cassent au niveau de la bride de fixation en libérant la majeure partie de la pièce dans le concasseur. Le matériau étudié est un acier à haute teneur en chrome. Plusieurs techniques ont été employées pour caractériser ce matériau et détecter les causes qui sont à l’origine de ce problème. Les échantillons ont été analysés par spectrométrie X. La microscopie a contribué à la révélation de la microstructure et aussi à faire ressortir les éventuels défauts micro et macroscopiques existants. La diffraction des rayons X a aidé à détecter le type et la proportion des phases microstructurales. Voir les détails
Mots clés : Acier moulé, endommagement, marteau de concassage, usure, microstructure, défauts
Effect of heat treatment temperature on thestructural evolution of hot forged steel balls used forgrinding raw material in cement industry
The raw material preparation sector such as cementworks, the steel and mining sector is beginning to pay attention toforged balls as an alternative to the cast balls for their best usecharacteristics. The forging materials are stronger than thecasting material because of their fiber structure. The forgingtechnique, in contrast to the casting process, contributes to asignificant improvement of ball wear behavior during thegrinding process.The wear behavior depends on several factors including thechemical composition of the alloy, the type of microstructure andthe applied heat treatment. In this work we focus on the effect ofaustenitizing temperature on the type of the producedmicrostructure. Al the heat treatment parameters were fixed forall the samples except the austenitizing temperature. Threeaustenitizing temperatures are selected and a tempering at 250°C with a holding time of one hour followed by cooling has beencarried out. The study is carried out on medium micro-alloyedcarbon steel intended for heat treatment.To make clear the effect of the temperature on themicrostructural transformation, several investigations wereachieved. Optical and SEM microscopy was carried out toqualitatively characterize the phases A microstructural analysisusing the Rietveld method was conducted to access, for eachtemperature, the type and proportion of phases as well as thecrystallites size. Voir les détails
Mots clés : grinding balls, forging, heat treatment, characterization, XRD analysis, Rietveld refinement
EFFECT OF HEAT TREATMENT ON WEAR BEHAVIOUR OF FORGEDSTEEL BALLS
The raw material preparation sector such as cementworks, the steel and mining sector is beginning to pay attention toforged balls as an alternative to the cast balls for their best usecharacteristics. The forging materials are stronger than thecasting material because of their fiber structure. The forgingtechnique, in contrast to the casting process, contributes to asignificant improvement of ball wear behavior during thegrinding process.The wear behavior depends on several factors including thechemical composition of the alloy, the type of microstructure andthe applied heat treatment. In this work we focus on the effect ofaustenitizing temperature on the type of the producedmicrostructure. Al the heat treatment parameters were fixed forall the samples except the austenitizing temperature. Threeaustenitizing temperatures are selected and a tempering at 250°C with a holding time of one hour followed by cooling has beencarried out. The study is carried out on medium micro-alloyedcarbon steel intended for heat treatment.To make clear the effect of the temperature on themicrostructural transformation, several investigations wereachieved. Optical and SEM microscopy was carried out toqualitatively characterize the phases A microstructural analysisusing the Rietveld method was conducted to access, for eachtemperature, the type and proportion of phases as well as thecrystallites size. Voir les détails
Mots clés : grinding balls, forging, heat treatment, characterization, XRD analysis, Rietveld refinement
L’Etude du comportement à la corrosiondes aciers inoxydables supermartensitiques et martensitiques dans deux milieux corrosifs
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
Structural and tribological behavior of AISI L6 tool stee
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