Nombre total de résultats : 183
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Effect of root pass filler metal on microstructure and mechanicalproperties in the multi-pass welding of duplex stainless steels

Ahmed KELLAI, Azzedine Lounis, Sami KAHLA, Brahim IDIR  (2018)

This paper is focused on the estimation of the effect of root pass chemical composition, in multi-pass GTA Weldments, onmicrostructure and mechanical properties of duplex stainless steel welds.We used two different fillermetals, the super duplex ER2594 and duplex ER 2209. Microstructures of different passes of welded joints are investigated using optical microscope andscanning electron microscope. The relationship between mechanical properties, corrosion resistance, and microstructure ofwelded joints is evaluated. It is found that the tensile and toughness properties of the first weldment, employing the combinationof ER 2594 in the root pass and ER 2209 in the remaining, are better than that of the second weldment employing ER 2209 allpasses, due to the root pass grains refinement and its alloy elements content as chromium Cr and nitrogen N. The microstructureindicates the presence of austenite in different forms on the weld zone of ER 2209, same in the case of ER 2594, but with highercontent and finer grains size, in particularWidmanstätten austeniteWA. Potentiodynamic polarization tests of the first weld metalevaluated in 3.5% NaCl solution at room temperature have been demonstrated a corrosion resistance higher than that of thesecond weld metal. This work addressed the improvement of the corrosion resistance using appropriate filler metal withoutgetting any structural heterogeneity and detrimental changes in the mechanical properties. Voir les détails

Mots clés : Gas tungsten arc welding (GTAW), duplex stainless steel, Root pass, Filler metal, Microstructure and mechanical properties


R. Benchouieb, S. Achouri, W. Ghelloudj, S. TLILI  (2018)
Article de conférence

Hot deformation and static recrystallization behaviours of a low carbon 3% Silicon steel, which is ferritic structure at high temperatures, has been investigated using wedge-shape specimen with a single-pass hot rolling experiments. The hot-rolling tests were carried out at temperature of 900?C to 9mm thickness followed by holding at the same temperature (900oC). The volume fraction recrystallized increased with the increase in rolling reduction and holding time after rolling, although a plateau was observed in the relationship between the volume fraction recrystallized and the effective strain. The preferential area for the recrystallization was the previous grain boundaries, particularly triple points of boundaries where the strain was concentrated. An inhomogeneity of recrystallization in the transverse sections through the thickness of the deformed wedges was observed. It was concluded that in this fine grain size material of 3% Silicon steel, the knowledge of deformation and recrystallization behaviors needs better control of strain and temperature under wedge-shape material. Voir les détails

Mots clés : 3% Silicon steel, wedge-shape specimen, hot rolling, deformation variables, dynamic recovery, static recovery, static recrystallization.


Article de conférence

With the complex examination of raw material from a Sig deposit in Algeria in the region of Mascara area, physical, chemical and mineralogical properties of diatomite have been defined. It has been found that it is a dominantly amorphous material, sedimentary rock of the type silica-diatomite. The raw material consists of approximately 60% SiO2. Of the physical properties, more significant is porosity, which is higher than 60%. The raw material has a wide spectrum of possibilities for practical application: intensive absorbent for several types of liquids and chemical properties of the soil, natural insecticide, and filter water etc. For determination of the chemical contents, properties and origin of the raw material the following methods have been used, such as, chemical analysis, XRD analysis, optical microscopy and thermal analysis. Voir les détails

Mots clés : diatomite, X-ray, XRD, Sig.

Risk of Contamination of the Littoral lands by the mill scale in Annaba City-Algeria

B. Maalem, A. BALASKA, D. BERDJANE, L. Tairi, S. Djemili  (2018)
Article de conférence

A significant amount of scale is produced during casting of ingots and processing of hot-rolled products. In the El Hadjar steel complex, during the various rolling operations, the amount of scale produced is approximately 0.1% of the annual production of the rolling mills. The quality of the thin sheet during rolling is affected by the behavior of the iron oxide layers formed on their surfaces. For this reason, acids and oils are used for the descaling of slabs and billets by means of pressurized water. The calamine, contaminated by these various acids and used oils, is rejected and stored involuntarily on important areas and pollutes soil and groundwater. Micrographic observations as well as x-ray diffraction analysis have shown that calamine consists mainly of iron oxides. Hematite and magnetite become the main components for oxidation times greater than 1 hour. Characterization tests have shown that calamine is dense (ρ = 4.8 g/cm3), its particle size is variable depending on the degree of oxidation (from 0.5 to 10 mm). Simultaneous thermal analysis showed that an increase in mass of the calamine sample with a release of heat. Studies are underway for the physico-chemical characterization of the soils of the storage areas. Voir les détails

Mots clés : Scale, Risks, soil, thermal analysis, granulometry, X-ray diffraction

Infiltration behavior of Cu and Ti fillers into Ti2AlC/Ti3AlC2 compositesduring tungsten inert gas (TIG)brazing

N. Chiker, A. Haddad, Y. Hadji, M.E.A. Benammar, M. Azzaz, M. Yahi, T. Sahraoui, M. Hadj, M.W. Barsoum  (2017)

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

Effect of Welding Process on Microstructure and Mechanical Properties of Duplex Stainless Steel Welds

A. Kellai, A. LOUNIS, S. Kahla, A. Boutaghane  (2017)
Article de conférence

The purpose of this study is a comparison between the effect of two electrical arc welding processes, on the structural and mechanical behavior of 2205 duplex stainless steel weldments, the first one is the manual process GTAW and the second one is the automatic process SAW. This effect has been identified and examined in the different welding area namely, the base metal BM, the heat affected zone HAZ and the weld metal WM, using optical metallographic techniques and mechanical methods by hardness tests. Voir les détails

Mots clés : duplex stainless steel, welding, microstructure, mechanical properties


R. Benchouieb, D. BERDJANE, S. Achouri, O.GHELLOUDJ, F. LEMBOUB  (2017)
Article de conférence

An approximate model for predicting static recrystallisation of ferritic stainless steel type 430, in hot rolling is proposed. In this model, the effect of variables such as strain, strain rate, temperature and initial grain size were considered during hot rolling operations. A set of integrated mathematical models for predicting static recrystallisation evolution during hot rolling has been developed through laboratory research work experiments. It consists of many sub-models such as percentage of recovery, recrystallisation kinetics, time for 50 percent of recrystallisation, recrystallised grain size and grain growth. Some of the most important theoretic basic approaches to describe the kinetics of primary recrystallisation were first independently developed and comprehensive portrayed by Johnson and Mehl, Avrami as by Kolmogorov (Often named the JMAK-theory).The quantitative determination of the effects of these variables obtained, analysed and compared in the context of the recrystallisation kinetics of this material.The predicted results are in good agreement with measured of laboratory tests. The results of constitutive models based on semi empirical equations will be compared in the next publication to more sophisticated models based on cellular automata, vertex and Monte-Carlo-Potts methods. Voir les détails

Mots clés : ferritic stainless steel, hot rolling, Static recrystallisation, Mathematical model.

Comportement structural et mécanique dessoudures en aciers inoxydables austénitique etduplex réalisées par le procédé TIG

A.KELLAI, A. Boutaghane, B. Boussiala, S. Kahla, S. Dehimi  (2015)

L’objet de cette étude étant de connaître lesdifférentes variations structurales et mécaniques après un cyclethermique de soudage de deux aciers inoxydables de hauteperformance (austénitique AISI 316L et duplex AISI 2205), quisont très utilisés dans tous les secteurs, particulièrementl’industrie pétrolière. On a utilisé le procédé TIG, c’est unprocédé à arc électrique, caractérisé par son apport thermiqueintense et précis aisément automatisé, l’état microstructurale desassemblages soudés a été analysées par des observationsmétallographique optique de différentes zones à savoir : la zonefondue ZF, la zone affectée thermiquement ZAT et le métal debase MB. Finalement les changements microstructurales ont étéargumentés par une filiation de micro-dureté. Voir les détails

Mots clés : Acier inoxydable austénitique, duplex, soudage TIG, micro-dureté et contrôle

Elaboration par pulvérisation cathodique magnétron de couches minces en vue de leur utilisation comme biomatériaux. Caractérisation à l’usure et à la corrosion.

Chems Eddine RAMOUL (En préparation)
Thèse de doctorat

Depuis les deux dernières décennies les prothèses orthopédiques (de genoux, de hanches..) fabriquées en alliages métalliques (alliage de titane, CoCrMo, aciers inoxydables…) sont recouvertes d’un dépôt de céramique (nitrures, oxydes…) ou en HAP (hydroxyapatite) dans le but d’accroître la bio réactivité de leur surface mais aussi leur résistance à l’usure et à la corrosion. Cependant le système interaction matière vivante/biomatériaux reste peu étudié et donc méconnu notamment le problème des infections toujours présentes. C’est précisément dans cette optique que se fera ce travail de doctorat. On se propose donc de développer de nouveaux matériaux ternaires ou quaternaires à base de Me (avec Me= métal tel Ti, Zr, Ag…) par pulvérisation magnétron sur divers substrats pour améliorer leur résistance à l’usure et à la corrosion, tribo-corrosion. Ces matériaux seront élaborés sous forme de couches minces par un dépôts physiques en phase vapeur. L’un des objectifs de ces travaux de recherche sera de vérifier s’il existe une relation entre les propriétés mécaniques et structurales des matériaux obtenus et leur comportement biologique. Voir les détails

Mots clés : biomatériaux, tribologie, corrosion

DSC analysis of commercial Cu-Cr-Zr alloy processed by equal channel angular pressing

K. ABIB, F. HADJ LARBI, L. Rabahi, B. Alili, D. Bradai  (2015)

Samples of a commercial Cu-1Cr-0.1Zr (mass fraction, %) alloy were subjected to equal channel angular pressing(ECAP) up to 16 passes at room temperature following route Bc. Differential scanning calorimetry (DSC) was used to highlight theprecipitation sequence and to calculate the stored energy, recrystallization temperature and activation energy after each ECAP pass.On another hand, electrical properties were correlated with the dislocation density. Results show that the stored energy increasesupon increasing ECAP pass numbers, while the recrystallization temperature decreases significantly. Voir les détails

Mots clés : equal channel angular pressing (ECAP), Cu-Cr-Zr alloy, differential scanning calorimetry (DSC), electrical conductivity, stored energy