Sciences et génie des matériaux
Rotary friction welded C45 to 16NiCr6 steel rods: statistical optimization coupled to mechanical and microstructure approaches
In the present work, the dissimilar joints between C45 carbon steel and nickel-chromium 16NiCr6 steel rods were produced usingrotary friction welding process. Statistical analysis based on response surface methodology (RSM), microstructural examinationusing scanning electron microscopy with backscattered electron diffraction (EBSD) and mechanical tests were performed toinvestigate the friction weld joints. The results showed that friction time and rotation speed were the most effective parameters onthe weld joint quality with the highest t-ration of − 4.27, where the maximum bending strength of 1406.9 MPa was obtained at2000 rpm for 13 s friction time. Increasing friction time to 13 s resulted in remarkable decrease in grain size (about 35%) at theweld interface, which increased the hardness (350HV0.1) and elastic modulus (260 GPa). Voir les détails
Mots clés : Rotary friction welding . RSM methodology . Microstructure
Dissimilar FSW of AA2024 and AA7075: Effect of materials positioning and tool deviation value on microstructure, global and local mechanical behavior
In this work, the effect of material location and tool deviation on the global and local mechanical behavior of dissimilar AA2024/AA7075 friction stir weld joints was investigated. The results showed that increasing the tool deviation value up to 1mm towards the AA2024, fixed in advancing side, improved the material mixing quality and enhanced the grain refinement in the stir zone. It was found that the highest ultimate tensile strength was obtained when the AA2024 alloy was fixed in the advancing side for 1mm tool deviation towards this material. Above this deviation value, a gradual decrease of the global mechanical properties of the weld joints was noticed. Digital image correlation (DIC) technique coupled to tensile testing revealed an improvement of local strain in the stir zone and the heat affected zones of the dissimilar joints when AA2024 alloy was positioned in the advancing side. Voir les détails
Mots clés : Dissimilar friction stir welding, tool deviation, DIC, mechanical properties, microstructure
Effect of WC-Co cermet positioning and Ni-Cr interlayer on the microstructure and mechanical response of the dissimilar WC-Co / AISI 304 L rotary friction joint
In this work, incompatible properties of WC-Co cermet and AISI 304 steel were combined in the same component using rotary friction welding (RFW) process. The dissimilar joints were performed using a ductile NiCr interlayer with the change in the WC-Co cermet positioning i.e., fixed rotary side and feeding side. Similar microstructure across the weld joints was obtained of the different welding configurations that produced similar behavior in hardness and elastic modulus. A diffusion zone was formed at the weld interface as a result of the mutual inter-diffusion of both cermet (W and Co) and steel elements (Fe, Cr and Ni) that enhanced with the insertion of the interlayer when the cermet was fixed in rotary side. The introduction of the NiCr interlayer was beneficial to relax the residual stresses and improving the shear strength of the WC-Co cermet/AISI 304 L steel joints, which is promising technology for drilling tools industries. Voir les détails
Mots clés : Rotary friction welding WC-Co cermet NiCr interlayer Interface Microstructure Mechanical properties
Effect of aging temperature on the microstructure, local-mechanical properties and wear behavior of a UNS S32750 super-duplex stainless steel
In this paper, the effect of aging temperature on the microstructure, local-mechanical properties and wear behavior of a UNS S32750 super-duplex stainless steel is investigated. A massive preferential precipitation of σ phase and Cr2N is detected at the periphery of ferrite with an increase in their extent as aging temperature increases. Simultaneously, the δ phase decomposition is accentuated with temperature and reaches its maximum at 850°C.This behavior results in an enhancement in hardness and Young’s modulus accompanied by a higher plasticity ratio. The wear resistance of the aged samples is investigated in terms of friction coefficients and wear rates against two counterparts. The wear performance follows σ phase presence, the higher σ phase extent, the higher the wear resistance. It is found that the change in wear mechanisms in the 850°C aged samples from abrasive against AISI-304L counterpart to adhesive-oxidative against Al2O3 counterpart is responsible in the increase in wear resistance. Voir les détails
Mots clés : 2507 SDSS, Aging temperature, microstructure, precipitates, Nano-indentation, Wear resistance.
Effect of WC-Co cermet positioning and NiCr interlayer on the microstructure and mechanical response of the dissimilar WC-Co / AISI 304 L rotary friction joint
In this work, incompatible properties of WC-Co cermet and AISI 304 steel were combined in the same component using rotary friction welding (RFW) process. The dissimilar joints were performed using a ductile NiCr interlayer with the change in the WC-Co cermet positioning i.e., fixed rotary side and feeding side. Similar microstructure across the weld joints was obtained of the different welding configurations that produced similar behavior in hardness and elastic modulus. A diffusion zone was formed at the weld interface as a result of the mutual inter-diffusion of both cermet (W and Co) and steel elements (Fe, Cr and Ni) that enhanced with the insertion of the interlayer when the cermet was fixed in rotary side. The introduction of the NiCr interlayer was beneficial to relax the residual stresses and improving the shear strength of the WC-Co cermet/AISI 304L steel joints, which is promising technology for drilling tools industries. Voir les détails
Mots clés : Rotary friction welding, WC-Co cermet, mechanical properties, NiCr interlayer, Interface
Materials sciences And Engineering, (MSE’22)
This work presents a study on the elaboration and characterization of Hydroxyapatite obtained from bovine bone calcined at 900°C for 3 hours with a particle size of around 125 μm and sintered at 1100°C. A prepared biological solution (Simulated Body Fluid, SBF), to study the biological response of our elaborated powder.We carried out a characterization by scanning electron microscopy (SEM) in order to observe the formation of the apatite layer during the immersion time. Voir les détails
Mots clés : hydroxyapatite, SBF, Biological response, Osteoconductivity
Impact of rare-earth elements on the corrosion performance of binarymagnesium alloys
The corrosion behaviour of Mg-0.3Ce, Mg-0.41Dy, Mg-0.63Gd, Mg-1.44Nd and Mg-1.43La (wt.%) alloys in3.5 wt% NaCl solution was investigated using electrochemical tests. The as-cast microstructures of theMg-RE alloys were characterized by the presence of second phases (MgxCe, Mg41Dy5 , Mg12Gd, Mg12Nd, Mg41Nd5, Mg24Nd and Mg12La) with different volume fraction and distribution. Results show that thecorrosion mechanism was altered from uniform to localized corrosion mechanism depending on thespecific RE alloying elements. The corrosion resistance of the Mg-RE alloys is increasing in the followingorder: Mg-1.43La, Mg-1.44Nd, Mg-0.3Ce, Mg-0.63Gd and Mg-0.41Dy. Accordingly, the corrosionmorphology in the best resistant Mg-0.41Dy alloy and the worst Mg-1.43La alloy were observed andcompared after 2h and 24 h of immersion using SEM-EDS, XPS and XRD analysis. The formation of theDy 2 O 3 oxide prevents the Mg-0.41Dy alloy from pitting corrosion and lead to an excellent corrosionsurface even after 24 h of immersion. Meanwhile, the presence of a high fraction of the Mg 12 La phasealong the grains boundaries in the Mg-1.43La alloy causes severe pitting corrosion by acting as anodicphase. Voir les détails
Mots clés : corrosion resistance, Chloride ion, Magnesium Alloy, Rare earth element
Stability, rigidity and thermal vacancies evolution in Fe-Cr-Mn alloys with C and N additions: DFT and Wagner-Schottky model investigations
The pseudo-potential Density Functional Theory (PP-DFT) combined with the statistical Wagner-Schottky model, are applied to study the Fe-xMn-(26-x)Cr-5Mo-3Cu-0.6C-0.7N austenitic alloys (x 1⁄4 6, 9, 12 and 15 wt%). The obtained results show that the rigidity and the thermal vacancy behavior isvery sensitive to the system composition. The overall system stability is found to be governed by thepresence of nitrogen. Both carbon and nitrogen favor the vacancy creation at T~1200K and prevent thethermal vacancy activation at T~1600K. Interestingly, beyond 1273K, carbon atom could migrate towardthe substitution sites while nitrogen atoms do not leave their favorable octahedral sites. Voir les détails
Mots clés : Fe-Cr-Mon Alloys;, Structural Stability;, Rigidity, Thermal Vacancies, DFT, Wagner-Schottky Model
Characterization and analysis of novel natural cellulosic fiber extracted from Strelitzia reginae plant
The purpose of this study is to evaluate in detail the usability of new cellulosic fibers extracted from the stem of the plant Strelitzia reginae, as a potential reinforcement for polymer composites. The morphological, physical, thermal, and mechanical properties of fibers were addressed for the first time in this paper. Both untreated and alkali-treated fibers were characterized, using scanning electron microscopy (SEM), Fourier-transform infrared, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), optical microscope, and X-ray diffraction (XRD) and applying tensile test for determining the mechanical behavior. For both fiber treated at one hour (T1H) and at four hours (T4H), the stem anatomy and fiber SEM micrographs showed a strong presence of fiber cells. Thermogravimetry and DSC showed that the fiber was thermally stable up to 233°C for untreated fiber, 254 and 240°C, respectively, In single-fiber tensile tests, it was observed that the fibers extracted from the stem of Strelitzia reginae were strong. The mean values of Young’s modulus exhibited by untreated fibers and treated (T1H) and (T4H) are, respectively, 9.89 GPa, 12.08, and 18.39 GPa. Also mean values of tensile strength are 271.79, 306.23, and 421.39 MPa. The XRD reveals the presence of cellulose with a Crystallinity Index of 70% for raw fiber and 72% for the treated one. Fourier-transform infrared analysis well demonstrated the effect of chemical treatment. It can be concluded from the results of all above experiments that the Strelitzia reginae fibers (SR) could serve as a possible reinforcement in composite materials. Voir les détails
Mots clés : natural fibers, Biocomposite, Surface analysis, SEM, FT-IR, thermal analysis, TGA, XRD, DSC
Elaboration et Caractérisation des Cuprates Supraconducteurs de type YBCO
In this work, we prepared YBCO samples by sol-gel process and the gel decomposition studied by TG/DSC, which shows the X-ray diffraction due to the fact that the samples contained a preponderant phase (YBa2Cu3O7). SEM images showed the polycrystalline structure of samples with grain size between 2 and 3 µm and high porosity rate. Longitudinal and transverse ultrasonic velocity and attenuation measurements were performed on 3 mm thick samples. The experiments were performed at room temperature (300 K). The objective of this technique is ultrasonic characterization. Voir les détails
Mots clés : YBCO, sol-gel, XRD, DTA, Ultrasound