Papers by Author: Mosbah Zidani

Abstract: The main objective of this work is to optimize welding parameters of AISI 430 FSS welds, focused to minimization of ferrite grains size using Taguchi’s design. Two input parameters of speed and welding current; were chosen to select the minimum grain size and to ascertain their effects on ferrite grain size. ANOVA method was used to evaluate the influence of varying factors on the overall quality of welds. Optimal combination of the parameters were be predicted by S/N analyses, it was accessed on employing an 80 A with 6mm/s. Experimental characterizations of optimum weld joint were performed by using tensile test assisted by image correlations, optical and electronic microscopy. As a result, welding speed had the main influence on grain size by 84.30%. Optimum welding parameter offered finest microstructure with low rate of martensite precipitates in both fusion zone and heat affected zone, and best combination of strength and ductility, it presented a homogeneous distribution of tensile stresses that caused a ductile fracture in base material. ,it is found that that optimized welding parameters permit to give greater resistance to corrosion, which exhibit a lower corrosion current, indicating that coarse ferrite grains are more susceptible to corrosion compared to fine grains.

Abstract: This study was mainly oriented on the evolution of the crystallographic texture as a function of the deformation resulting from the industrial wire drawing process. This, in fact, will make it possible to establish a relationship between the microstructure and the crystallographic texture in the medium carbon steel wires obtained by industrial wire drawing process and used in the manufacture of spring mattresses in order to minimize the loss of material and to satisfy the users of this product.During this study, a medium-carbon steel wires was characterized by two analytical techniques. The scanning electron microscopy (SEM) to monitor the microstructure evolution and the electron backscatter diffraction (EBSD) for the crystallographic texture analysis. The EBSD results are processed with OIM (Orientation Imaging Microscopy) analysis software.

Abstract: Duplex treatments are surface modification techniques used to enhance the surface properties of steels. In this study, hard chromium electroplated AISI 4340 steel was plasma nitrided in pure nitrogen gas at 600°C for 90 min. The structural and morphological properties were analysed by an X-ray diffractometer and a scanning electron microscope (SEM), respectively. The hardness profile was obtained by a multicycle nanoindentation test and the tribological properties by a ball-on-disk test at room temperature. The results showed that the duplex layer was composed mainly of Cr₂N and it had a rough surface morphology with a network of micro-cracks. The highest values of hardness were registered in the nitrogen diffusion layer beneath the outer porous thin layer. The friction coefficient and the specific wear rate after plasma nitriding were reduced by 3 and 5 factors, respectively.

Abstract: In this paper, the evolution of texture in the ferrite phase and mechanical behavior of cold-drawn pearlitic steel wires produced for strand manufacturing at Trefisoud company was investigated. Wire drawing induces the development of dislocation density, reduction of interlamellar spacing and the refinement of grains size which leads to a strong hardening of the wires. That explains the increase of the tensile strength from 1242 MPa to 2618 MPa with higher deformation. Also, the cementite lamellae are rotated toward the drawing axis and the thickness of lamellae further decreases when strain level increases, this phenomenon leads to a somewhat fibrous structure. The quantitative analysis obtained by EBSD data shows the development of a strong (<110> // ND) texture of the ferrite phase leading to a structural transformation from isotropic to anisotropic.

Abstract: In this paper, the study of precipitation reaction in the aluminum alloy known as AGS 6101. For the case of Cold drawn wires process in the open air space and at room temperature for two years, we inspect first the presence of precipitates in the microstructure and study the effect of heat treatment on the activation of this phenomenon [1]. The second objective of this work is to see the effect of natural and thermal aging on the microstructural evolution of cold-drawn aluminum wires (AGS) 6101 [2-5]. The characterization methods used in this work are optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction.

Abstract: The aim of this work is to study the difference between the crystalline phases of used fluxes and obtained slags after Shielded Metal Arc Welding (SMAW). It is well known that The weld pool solidifies into the weld metal while the lighter molten flux floats on the top surface and solidifies as a slag layer that can be easily removed .The effects of individual flux ingredients as well as their interaction effects on weld metal composition have been investigated in this paper. The mass concentrations between fluxes (FA, FB and FC) and slags (SA, SB and SC) summarize the physico-chemical behavior of elements transfer between base metal, filler metal, flux and slag forming during welding of pipelines by SMAW process. The analysis of different fluxes phases and slags by X-ray diffraction allowed to detect the presence of different crystalline phases, which were formed at low temperature (T <1000°C) heat treatments, and during fluxes confection. As for the slags, the presence of new crystalline phases which have been formed at high temperatures.

Abstract: This paper studied the influence of cellulosic flux on the chemical composition, microstructure, formation of inclusions and micro hardness of X42 welded steel. The chemical compositions of the used fluxes are FA: E6010 and FB: E8010-P1, with electrodes has low carbon content. The welding conditions are not constant. The fluxes (FA and FB) have a high content of TiO₂ and SiO₂ and a low Ti and Si content was also detected in the internal (P1) and external (P3) passes. But there was an increase in the Ti content in the fusion zone (P1, P2 and P3) of the different passes gradually, compared to the base metal. The microstructure of the fusion zone (P1, P2 and P3) for each flux is mainly composed of acicular ferrite. The mass concentration variation of Mn is more elevated through the centers of the fusion zone passes (P1, P2 and P3) with the used fluxes. White and black non-metallic inclusions are observed, regardless of used flux. The micro-hardness in fusion zone varies according to the variation of the equivalent carbon in the different electrodes.

Abstract: This study focuses on the evolution in the microstructure, texture and mechanical properties of medium carbon steel wires obtained by wire drawing at Tréfissoud Company for the manufacturing of the spring mattress. Wire drawing induces elongation of grains in the direction of drawing with the development of the <110> fibre texture parallel to the wire axis. Kinking and bending of cementite lamellae were observed during the drawing process. The work was carried out respectively on three states, wire rod and drawn states for two different amounts (ε %=43,6 and 60 %), using the optical and SEM microscopy, electron backscatter diffraction and X-ray diffraction analysis for examination of the microstructure and texture evolution, the hardness Vickers and tensile test to follow the curing of the studied wires.

Abstract: The scope of this work is to study of microstructural changes and mechanical properties during natural and artificial ageing treatment of AGS Alloy wire cold drawn with different deformation at ENICAB in Biskra. And as well to know the phase formation during different deformation of aluminum alloys wires. as well as the combined influence of the plastic deformation rate and the aging temperature. Wire section reduction shows a change in microstructure and texture. The methods of characterization used in this work are: scanning electron microscope and X-ray diffraction, micro hardness (Hv).

Abstract: The objective of this work is the development of a Fe-W-Ni sintered steel obtained by the powder metallurgy technique. The latter is widely used today for the design of new alloys based on powders (iron) to meet industrial requirements in strength and wear characteristics. The proposed alloy is based on iron mixed with 5% nickel and various percentages (5, 10, 15 and 20%) of tungsten. The effect of the tungsten W content on mechanical and structural properties is presented.