Sciences des matériaux

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Inhibition Effect of 2,2’-bipyridyl on the Corrosion of Austenitic Stainless Steel in 0.5M H2SO4

Amel GHARBI, ABDELAZIZ HIMOUR, Sihem Abderrahmane, KARIMA ABDERRAHIM  (2018)
Publication

The corrosion inhibition of AISI309 austenitic stainless steel by 2,2'-Bipyridyl in 0.5MH2SO4 at 298K was studied using the mass loss’ method, the potentiodynamic polarization (Tafel), the linear polarization (LRP), and the electrochemical impedance spectroscopy (EIS). The results showed a mixed inhibition mode and an increase in the charge transfer resistance, due to inhibitor molecules' adsorption at steel surface. This latter obeys to Langmuir isotherm. The observation by scanning electron microscopy (SEM) and the analysis by energy dispersion spectrometry(EDS) confirm an inhibitor film’s presence. The calculated inhibition efficiencies are in accordance with 87.78% maximum value. Voir les détails

Mots clés : AISI309, 2, 2'-Bipyridyl, EIS, Tafel, corrosion, inhibition

Effect of Environmental Media on the ElectrochemicalBehavior of API X70 Pipeline Steel

A. GHARBI, B. Benayad, O. Assala, K. BOUHAMLA, O. GHELLOUDJ, S. Chettouh, S. REMILI, A. Bachiri  (2021)
Publication

This work investigates the corrosion behavior of X70 steel in different environments: sea sand, desert sand, mud, and seawater. The principle of extracting solutions from these media consisted of mixing a soil material with distilled water, and the mixture was agitated using an automatic agitator, which resulted in the extraction of the solution. Potentiodynamic polarization and electrochemical impedance tests are used to characterize the samples in both media. The results show that the pipeline steel X70 has an excellent corrosion resistance in the sea sand solution, resulting in a low corrosion current density compared to other media. The impedance diagrams for both media are characterized by two capacitive loops, the first loop is attributed to charge transfer processes and the second loop is related to diffusion phenomena. The observation of corroded surfaces shows that the corrosion mechanism in different media is by pitting. Voir les détails

Mots clés : pitting, sea sand, seawater, corrosion

Inhibition Effect of 2,2’-bipyridyl on the Corrosion of austenitic Stainless Steel in 0.5M H2 SO4

Amel GHARBI, ABDELAZIZ HIMOUR, Sihem Abderrahmane, KARIMA ABDERRAHIM  (2018)
Publication

The corrosion inhibition of AISI309 austenitic stainless steel by 2,2'-Bipyridyl in 0.5MH2SO4 at 298K was studied using the mass loss’ method, the potentiodynamic polarization (Tafel), the linear polarization (LRP), and the electrochemical impedance spectroscopy (EIS). The results showed a mixed inhibition mode and an increase in the charge transfer resistance, due to inhibitor molecules adsorption at steel surface. This latter obeys to Langmuir isotherm. The observation by scanning electron microscopy (SEM) and the analysis by energy dispersion spectrometry(EDS) confirm an inhibitor film’s presence. The calculated inhibition efficiencies are in accordance with 87.78% maximum value. Voir les détails

Mots clés : AISI309, 2, 2'-Bipyridyl, corrosion, EIS, Tafel

Tribocorrosion Dependence on Porosity of TiNi Alloysin Phosphate‑Buffered Saline Solution

KAHLOUL Latifa, MEDDAH Soumaya, Nasser Eddine BELIARDOUH, Alex Montagne, Mohamed Bououdina, Said Boudebane  (2022)
Publication

Degradations of implants during their service life lead to rejection because of corrosion and wear-related problems, i.e., toxicions and wear particles released into the human body. In this case, tribocorrosion tests are appropriate ways to investigate thesynergistic effect of the corrosion and wear phenomena, on the material implant in simulated body fluids. This study aims toanalyze the bio-tribology as well as the tribocorrosion performances of porous TiNi alloys, fabricated from elemental powdermixture (Ti, Ni) by powder metallurgy. The effect of the level in porosity, resulting from four (04) different cold pressing, wasinvestigated against alumina ball in phosphate-buffered saline solution (PBS) at 37 °C. SEM/EDS microstructural analysesrevealed the presence of various phases with TiNi as the predominant phase. Obtained results showed that the lowest frictioncoefficient was recorded for the sample with 33% in porosity rate when sliding against an alumina ball in dry conditions. Ahigh tribocorrosion resistance for all the studied TiNi compositions was also observed. Based on the corrosion parametersand the wear rate, the composition with the highest porosity exhibited the optimum performance. Voir les détails

Mots clés : TiNi alloys, Biotribolgy, Tribocorrosion, Porosity

HEAT TREATMENT AND WELDING EFFECTS ON MECHANICAL PROPERTIES AND MICROSTRUCTURE EVOLUTION OF 2024 AND7075 Aluminum ALLOYS

M. Hakem, M. KHATIR, RR. OTMANI, T.FAHSSI, N. DEBBACHE, D. ALLOU  (2007)
Publication

Aluminum alloys are sensitive to hot cracking during the welding operation, both liquidation cracking in the heat affected zone (HAZ) and solidification cracking in the weld can occur. The GTA Welding results of aluminum alloys 2024 T3 and 7075 T6 for 2 mm plate thickness with different parameters of welding are presented in this paper. Before welding, different alloys were heat treated at different temperature to follow the evolution of microstructure and mechanical properties. After welding, the strength of the materials in heat affected zone (HAZ) is reduced. This reduction on properties is due to the different phenomenon that occurs during welding Voir les détails

Mots clés : heat treatment, Aluminium alloys welding, hardness, Precipitation, tensile strength, yield strength, Microstructures

Pressureless sintering and tribological properties of in-situ TiC-Ni3(Al,Ti)/Ni(Al,Ti) composites

Nabil Chiker, Abdessabour Benamor, Adel Haddad, Youcef Hadji, Maamar HAKEM, Riad BADJI, Mohamed Labaiz, Mohamed Azzaz, Mohamed HADJI  (2021)
Publication

In this study, we report on the microstructure and tribological characterization of in-situ TiC and γ’-Ni3(Al,Ti)reinforced γ-Ni(Al,Ti) matrix composites, synthesized by in-situ reaction of Maxthal211 (Ti2AlC-Ti3AlC2, MAX phase) and Ni precursors. Three composites were elaborated from 10, 20 and 30 wt % of the MAX phase precursor which fully reacted with Ni-matrix at 1080 °C sintering temperature for 4 h; the MAX phase decomposed into TiC, and the released Al and Ti atoms diffused in Ni matrix forming γ-Ni(Al,Ti) solid solution and γ’-Ni3(Al,Ti)intermetallic. Scanning Electron Microscopy (SEM), X-Rays Diffraction (XRD) and Raman spectroscopy were used to study the different microstructures and worn surface characteristics. Dry sliding properties of the composites under different normal loads were studied using a ball-on-disc tribometer. Addition of 10 wt % MAX phase procured the highest hardness (1.35 GPa) which is two times higher than that of pure Ni. Whereas all there inforced composites exhibited better wear resistance. The formation of a lubricious layer during sliding and the good in-situ bonding between Ni/reinforcement phases, were the main cause to the enhanced wear resistance. Voir les détails

Mots clés : Metal matrix composites, Pressureless sintering, MAX phase, diffusion, In-situ composites, wear

Microstructure and Tribological Behavior of In SituTiC-Ni(Si,Ti) Composites Elaborated from Ni and Ti3SiC2 Powders

Nabil Chiker, Abdessabour Benamor, Youcef Hadji, Adel Haddad, Maamar HAKEM, Mohammed AZZAZ, TAHAR SAHRAOUI, Mohamed HADJI  (2020)
Publication

Herein, we study the effect of Ti3SiC2 on the microstructures and tribological properties of an in situ TiC reinforced Ni(Si, Ti) composites elaborated from Ni and Ti3SiC2 MAX phase powders against steel(100Cr6). Pressureless sintering at 1080 C for 4 h of Ni and Ti3SiC2 powders was used to elaborate these composites with 10, 20 and 30 wt.% of Ti3SiC2. The microstructures of the composites were investigated by scanning electron microscopy (SEM), x-rays diffraction and Raman spectroscopy. Standard ball-on-disk friction wear tests under different applied loads were conducted on the composites surfaces at room temperature. For the three elaborated composites, Ti3SiC2 was totally decomposed and transformed to TiC phase, while the released Si and Ti atoms from Ti3SiC2 diffused into Ni matrix forming Ni(Si, Ti) solid solution. As compared with reference (Ni) sinter, the addition of 20 wt.% Ti3SiC2 in the Ni matrix improved the hardness by  250%. The addition of Ti3SiC2 particles also had a beneficial effect on the tribological performance of these composites against steel. The worn surfaces of the elaborated composites under all applied loads are characterized by the presence of a lubricious Fe3O4-aFe2O3 tribofilms. The effect of chemical compositions and different applied loads on the wear mechanisms of the three elaborated composites is discussed. Voir les détails

Mots clés : In situ composites, MAX phase, Microstructures, wear

Effect of heat treatment on microstructure and tribological behavior of friction stir processed Al2O3-reinforced AA2024-T351 matrix

Adel Haddad, Abdessabour Benamor, Nabil Chiker, Youcef Hadji, Mustapha Temmar, Maamar HAKEM, Riad BADJI, Said ABDI, Mohamed HADJI  (2021)
Publication

In the present work, 2024-T351 Al alloy reinforced with alumina particulates (Al2O3p) was elaborated using friction stir processing (FSP). The effect of solution heat treatment followed by subsequent aging on microstructure, hardness, and tribological behavior is discussed. It was noticed that the hardness of the as-FSPed 2024-T351/Al2O3p was slightly enhanced in comparison to the as-received AA2024-T351 material, whereas the resulting wear resistance was remarkably improved. After heat treatment process, the composite volume increased, and swelling and pores were created at the processed area. The heat treatment caused a degradation in wear resistance compared to as-FSPed composites. The precipitation mechanism changed forAA2024/Al2O3p; reactions occurred at grain boundaries between Al2O3 and Cu or Mg, causing their depletion from the Al matrix. Intriguingly, the precipitation mode in heat-affected zone of the matrix also changed to grain boundary precipitation. Voir les détails

Mots clés : Friction stir processing, Metalmatrix composites, wear, friction

Influence of isothermal aging in LDX 2101 duplex stainless steel on the microstructure and local properties

N Ouali, B Cheniti, B Belkessa, B Maamache, R Kouba, M Hakem  (2021)
Publication

In the present work, the interface morphology and the evolution of nitride precipitates in LDX 2101 stainless steel isothermally treated at 750 °C for various aging times were investigated. The microstructure results showed that the Cr2N nitrides precipitated along the δ/γ interface with 200 nm in length and continue to grow to 2 μm after 240 h of aging. However, only Cr2N nitrides were found at the δ/δ interface after long term of aging. Atomic force microscopy (AFM) analysis revealed that Cr2N nitrides andCr23C6 carbides started to precipitate after the first 10 min of aging with a small needle shape of the former and specific triangular morphology of the latter. The evolution of hardness and Young’s modulus of the interfaces, performed with nano-indentation measurements, showed that the δ/γ interface became harder (4.1 ± 0.2 GPa) with increasing aging times, whereas negligible changes in the hardness and elastic modulus were recorded at the δ/δ interface. 3D topographic analysis of the immersed surfaces revealed that the susceptibility of δ phase to preferential dissolution in 3.5% NaCl solution increased with aging time. This behavior was manifested by the important imperfections of δ phase, the high surface roughness (55.7 nm), and the deep corrosion pits (30 nm) along the δ/γ interface and around the Cr2N nitrides. Voir les détails

Mots clés : microstructure, Interface, precipitates, Nano-hardness, Surface degradation

Physical properties investigation of Fe1−xAlx(x≤50%-at) alloys using DFT and Wagner-Schottky model

I Berrached 1, M Gallouze 1, L Rouaiguia 1, L Rabahi 1, T Grosdidier 2, M Drir A Kellou  (2020)
Publication

Atomistic modeling based on the Density Functional Theory (DFT) is used to study thestructural, magnetic, electronic and mechanical properties of Fe1−xAlx alloys (x≤50%-at) with and without B, C and N additions over the selected range of Al atomic concentration. It is shownthat a singularity around x Al ∼ 40%-at is observed for the lattice parameters while the magneticmoment decreases uniformly without unexpected trend. The enthalpies of formation indicatethat the presence of B stabilizes the system for Al concentration in the range of 25%-at Voir les détails

Mots clés : iron aluminides, Magnetic Properties, elastics proprieties, Electronic structures, DFT calculations, thermal defects, Wagner-Schottky Model