Métallurgie
Affinement des pics de diffraction par mÈthode Rietveld
La caractÈrisation d'une soudure en Ti-6Al-4V a impliquÈ la rÈalisation d'essais de diffraction des rayons X sur des Èchantillons prÈlevÈs dans diffÈrentes zones du joint soudÈ, notamment le mÈtal de base, la zone affectÈe thermiquement et la zone fondue. Pour affiner et indexer les pics des diffractogrammes, la mÈthode d’affinement Rietveld a ÈtÈ utilisÈe. L'objectif de cette Ètude est de prÈsenter le principe de l'affinement par la mÈthode Rietveld et de dÈcrire les diffÈrentes Ètapes en utilisant le logiciel MAUD (Materials Analysis Using Diffraction). Par la suite, une Èvaluation de la qualitÈ de l'affinement a ÈtÈ rÈalisÈe grâce aux paramètres d’affinement, ainsi que la dÈtermination de la taille des cristallites et de la microdÈformation. Voir les détails
Mots clés : Affinement Rietveld, MAUD, Ti-6Al-4V, tutoriel.
Soudabilité de l’alliage de titane TA6V parle procédé TIG
L’alliage TA6V est l’alliage de titane le plus utilisé en industrie, en effet il est souvent choisi pour la fabrication de pièces structurelles dans lesavions, les hélicoptères, les implants médicaux, les composants automobileset d’autres applications exigeantes, tout ça grace à ses propriétés physicochimiques incontournables ainsi qu’à sa bio-compatibilité. Il s’en suit doncnaturellement que les procédés de soudage qui lui sont appliqués font l’objet de préoccuopation majeure pour les ingénieurs .Ce travail a pour objectif d’étudier la soudabilité de l’alliage TA6V detitane par procédé TIG, en mettant en exergue les e昀昀ets de ce procédé desoudage le comportement métallurgique et mécanique de l’alliage TA6V.Pour ce faire, il a été question de suivre un protocole expérimental rigoureux pour établir une caractérisation métallurgique et mécanique quia regroupé plusieurs types d’analyses notemment l’analyse par DRX, lesessais de traction interpretés par corrélation d’images numériques etc.Les résultats trouvés ont été interpretés et ont fourni des informationscruiciales nous permettant enre autres d’évaluer la qualité des soudures etleur impact sur la structure et les propriétés du matériau en question. Voir les détails
Mots clés : Alliage TA6V, soudage par procédé TIG, soudabilité, caractérisat
Effect of rotational speed and copper interlayer on the mechanical and fracture behaviour of friction stir spot welds of 5754 aluminium alloy
The application of joining processes requires advanced mechanical tests to control the joints quality. Generally, welded sheets are verified using tensile shear tests. However, few studies also recommend conducting tension peel and cross-tension tests. The present work evaluates the mechanical behaviour of 5754 aluminium sheets jointed by friction stir spot welding (FSSW). The influence of the rotational speed on joint strength was first compared to riveted assemblies. Then, sheets welded with pure copper interlayers were compared to the precedents. The results indicated that, without an interlayer, lower and intermediate rotational speeds lead to higher mechanical strength under tensile shear tests compared to riveted assembly. However, it performed worse under tension peel and cross-tension tests at all studied rotational speeds. By adding copper, the strength of welded sheets is globally improved under tensile shear tests. Nevertheless, under tension peel and cross-tension tests, it performed worse, although a slight improvement was observed for increasing rotational speeds. Two different failure morphologies and four fracture modes were observed regarding the different tested samples. Microhardness tests were also conducted, to relate the influence of the studied parameters on the joint s strength. Voir les détails
Mots clés : 5754 aluminium alloy, Failure and fracture modes, Friction stir spot welding, Mechanical testing, Microhardness
Caractérisation microstructurale et micromécanique d’unassemblage X60/316L, réalisé par Cladding, après déformation par laminage à chaud.
The objective of this work is to study the behavior of an assembly composed of a high yield strength steel and an austenitic stainless steel made by the cladding process under the effect of hot working followed by recrystallization annealing. Microstructural and micromechanical characterizations were performed on the whole multi-material and at the interface. In the present work, we have highlighted the importance of understanding and mastering the aspects of phase transformation and recrystallization mechanisms in order to optimize the mechanical properties by thermal and/or thermomechanical treatment. Voir les détails
Mots clés : Cladding, HSLA steel, stainless steel, thermomechanical treatment, recrystallization, phase transformation, Microhardness, annealing.
Dissimilar welding of aluminum alloys 2024 T3 and 7075 T6 by TIG process with double tungsten electrodes
The aim of this work is to study the metallurgical and mechanical properties of dissimilar assemblies of 2024 T3 and 7075 T6 structural hardening aluminum alloy by the TIG twine electrode arc welding process. It will include a weld performed according to optimized welding parameters followed by a study of the macroscopic and microscopic evolution of the dissimilar assembly (2024-7075) using optical and scanning electron microscopy (SEM); in addition, the phase compositions were analyzed with an energy dispersive spectrometer (EDS). Tensile and microhardness tests were performed. The tensile fracture was observed by SEM. This paper suggests that when the double tungsten electrode TIG welding is used, a stable arc has been formed with a good bead appearance. The heat dissipated by the arc generates several zones (molten zone (WZ), bonding zones (LZ), heat-affected zones (HAZ)) with different microstructures or precipitates of the type θ (Al2 Cu), S (Al2 Cu, Mg) and η (Mg Zn2), S (Al2 Cu Mg) are formed in the heat-affected zone (HAZ) of base metals 2024 and 7075 respectively. The microhardness is lower in the molten zone and higher in the heat-affected zone of 7075 T6 alloy, which cried out an embrittlement and a 44% and 37% drop in the tensile strength of 7075 T6 and 2024 T3 base metals respectively. Voir les détails
Mots clés : 2024 and 7075 aluminum alloy, Aluminum with structural hardening, microstructure, Double electrode TIG processing, Dissimilar welding
Influence of dry friction on the wear behavior of X52steel—experimental study and simulation using response surfacesmethod
Friction and wear phenomena alter the behavior of the material surface, where certain relevant parameters which characterizethe surface are influenced. Therefore, the objective of this work is to identify the parameters most influencing the frictioncoefficient (f), the wear rate (Ws), and the volume parameters (Vmc and Vvv) during the friction test. The friction tests werecarried out by adopting the methodology of 23complete planes with three factors (D, V, and Py), at two levels each. Theresults show a decrease in the wear rate when all three factors are at their highest level and a decrease in the friction coefficientwhen using minimum load on speed long distances. In addition, the mathematical models developed allow to reveala correlation between the test parameters (D, V, and Py), and the responses studied (f, Ws) in their study field. Moreover,the volume parameters Vmc and Vvv were evaluated during the tests, and the morphology of the worn surface shows thatthe friction under a load of 1 N leads to the predominance of an abrasive wear mechanism, while a load of 10 N promotesan adhesive wear mechanism. Voir les détails
Mots clés : Complete plans, modeling, friction coefficient, Wear rate, volume parameters
Effect of erosion parameters on the surface direction texture-Study by experimental plans
The aim of this work is to study the effect of solid particle impact erosion parameters of sand on the isotropy parameter "Std" which presents the direction of surface texture. The experimental methodology adopted for this experimental work is the Box Behnken plan with three factors, each at three levels (-1, 0 and +1), the parameters considered are: time "t", pressure "P" and angle of impact "θ". 3D roughness measurements were carried out using a laser source profilometer type Cyper-Technologie-CT100, in order to characterize the different surfaces after erosion test. The statistical analysis was carried out using the Mini Tab software, where a mathematical model was established showing the relationship between the input parameters (t, P, θ) and the output parameter "Std". This model predicts the "Std" response in the field of study as well as the parameters of the sandblasting regime. The results show the significant effect of the impact angle on "Std" and the interaction between the different parameters in the study domain, of which the highest value of "Std" is equal to 130 ° for an average time combined with low pressure and impact angle. Voir les détails
Mots clés : erosion, topography, roughness surface, Mathematical model, Box plans
Mechanical properties and bio‑tribological performance of PVD (Ta/ZrN)n multilayer coatings on UHMWPE in bovine serum lubrication
This work investigated the tribological performance of (Ta/ZrN)n multilayer coatings against ultrahigh molecular weight polyethylene (UHMWPE) material. Three multilayer coatings with different designs were deposited on Ti-6Al-4V substrate and subjected to wear testing under lubrication of diluted bovine calf serum. The results revealed an improvement in wear resistance of (Ta/ZrN) multilayer coatings and low coefficient of friction under an applied load of 1 N. High hardness, excellent biotribological properties, and low residual stresses were obtained in the multilayer coating with the thinnest ZrN as the topmost layer of 100 nm. This work demonstrates that Ta/ZrN multilayers can be promising coatings for prosthesis applications. Voir les détails
Mots clés : PVD coating, Ta/ZrN, UHMWPE, wear
Synthesis and tribocorrosion performances of multilayer (Ta/ZrN)n coatings
Multilayer thin coatings (~3 µm in thickness) were deposited using reactive radio frequency magnetron sputteringon Ti-6Al-4 V substrate for biomaterial applications. Films are a combination of hard zirconium nitride with pure tantalum, used to manage interfacial stress and to avoid crack growth. Alternating hard/ductile material is a biomimetic design inspired by nature(nacre-inspired materials). Tribocorrosion tests were performed in Hank’s solution at 37 C, under open circuit potential by using a ball-on-disk reciprocating tribometer. A tendency to high resistance against corrosion was found for all the samples. Coatings with a top 100 nm thick ZrN layer showed more noble potential as well as a reduction of both the friction coefficient and the wear rate during the sliding phase. The principal wear mechanism is related to a tribocorrosion layer formation. Voir les détails
Mots clés : Multilayer coating, Biomaterial, Tribocorrosion, Tantalum, Zirconium nitride, Magnetron sputtering
Microstructural Investigation and Oxidation Performance of Nickel‑Based Superalloys
An as-received IN738LC blade root material has been firstly characterized, in order to appreciate its structural, micro- structural and morphological properties. Different observations and analysis (OM, XRD, SEM/EDS, etc.) showed that our sample is mainly constituted of γ´ precipitates in a Ni-rich matrix (γ solution), a γ/γ´ eutectic and some carbides. After that, the oxidation behavior of IN738LC superalloy has been investigated to assess the oxidized formed layers. For this purpose, isothermal oxidation experiences have been carried out at 950 and 1150 °C for various times (24h, 48h and 72h). The differ- ent microstructures of oxides and substrate obtained after oxidation tests were observed and analyzed by scanning electron microscopy (SEM/EDS). The oxidation kinetics were monitored by samples weight change with time. Composition and phase evolutions, mean crystallite size and strain appeared in this superalloy, were determined by X-ray diffraction (XRD) patterns. Last, the adhesion of the growing oxides onto the substrate was evaluated by the scratch test. The main results of these investigations reveal that microstructure parameters strongly depend on temperature and durations of the process. Moreover, the oxidation kinetics of the alloys follows a parabolic rate law both at 950 °C and at 1150 °C. From XRD and EDS analysis, the major phases seen are Cr2O3, TiO2, Al2O3, NiO and NiCr2O4, which contribute to a better oxidation resistance. The oxide scales increase with time and temperature, they are compact, dense, distributed uniformly and adherent at 950°C/72h, while they are relatively larger and non-uniform at 1150 °C. On the other hand, the adhesion of the oxides at 1150°C is fairly weak, and oxidation products flake off quite easily, which indicated weakening of the protection. Voir les détails
Mots clés : Turbine blade, Inconel 738LC, Oxidation kinetics, microstructure, Strain, Adhesion