Papers by Author: Zakaria Boumerzoug

Abstract: The precipitation sequence of an Al-Mg-Si alloy depends on many parameters. In this study the natural aging effect on the activation energy of the precipitation sequence in the Al-Mg-Si alloy have been investigated by differential scanning calorimetry (DSC). The precipitation sequence of an Al-Mg-Si alloy has been established. The activation energy of the precipitation process was calculated using Kissinger model. The results obtained using this method showed a change in the activation energy for all precipitated phases. The activation energy of the metastable phases (β″ and β′) and the stable phase β formation in the Al-Mg-Si alloy aged at room temperature have been determined.

Abstract: The purpose of this paper is to study the cutting speed effect on mechanical and surface roughness (Ra) of XC18 steel. Scanning electron microscopy, hardness and roughness tests were used. We have found that the cutting speed affects the surface layer of a workpiece, induces hardening of the surface, and increases the surface roughness.

Abstract: The goal of this work is to investigate the recrystallization reaction in cold wiredrawn industrial copper. We have used a differential scanning calorimetry and X-ray Diffraction techniques. The stored and apparent activation energies have been determined by differential scanning calorimetry under isochronal conditions. The differential scanning calorimetry results have been analyzed using models developed by Kissinger, Ozawa, Boswell, and Starink. In addition, the transformed fraction, as a function of temperature, and some kinetic parameters have been determined. We have found that cold wiredrawn affects some microstructure proprieties of the material, such the increase of stored and apparent activation energies, and dislocation density after deformation.

Abstract: X-ray diffraction method has been used to analyze the residual stress distribution in weld region of an X70 pipeline steel before and after heat treatment. The welding process has been realized by industrial arc welding with circular weld seams. The effect of heat treatments on the level and the distribution of residual stresses were investigated. Stress distribution was characterized by relative high compressive stresses in weld seam just after welding. However, residual stress relaxation phenomenon was observed in weld region after heat treatments due to microstructure restoration and recrystalization. Optical microscope observation and Vickers hardness measurements were also realized as complementary microstructure characterization techniques.

Abstract: In this investigation, grain orientation has been studied in an industrial aluminium Al99.5 which has been welded by TIG process. The optical microscopy and EBSD (Electron Back Scattered Diffraction) were the main techniques used to illustrate the effect of welding on grain orientation in fusion zone and in heat affected zone. Epitaxial growth has been observed in weld joint and texture of each zone has been determined. On the other hand, the effect of isothermal heat treatment at 400 °C on homogenization of welded joint has been also studied. It was shown that the cube orientation {001}<100> is the dominant texture component in welded joint before or after heat treatments.

Abstract: In this study, the effect of the long natural aging on the precipitation sequence of Al-Mg-Si alloy was investigated by differential scanning calorimetry and hardness examinations. This investigation revealed that the natural aging has a negative effect on the artificial aging. The reason behind the influence of natural aging on precipitation behavior of the Al-Mg-Si alloy is assumed to be the formation of clusters and G.P. zone during natural aging. The hardening mechanism during artificial aging was explained.

Abstract: In this work, the effect of isothermal heat treatments on microstructure evolution and mechanical properties after welding by induction of A37 pipeline steel have been studied by scanning electron microscopy, hardness measurements, and tensile tests. Microstructural evolution in welded joint was identified after isothermal annealing from 200 until 900 °C.

Abstract: In this present investigation, the mechanical properties of industrial drawn copper wires have been studied by creep tests, tensile tests and hardness Vickers. The effect of prior heat treatments at 500°C for different time on the drawn wires behavior was the main goal of this investigation. We have found that these heat treatments influenced the creep behavior of drawn wires and recorded shape curves. The creep tests were applied under ambient atmosphere at 240 °C. The creep duration before rupture decreased with the prior heat treatment time. The creep tests results were confirmed by tensile tests. A relationship between the hardness and the ultimate tensile strength of this industrial material has been established. Optical and scanning electron microscopy observations have been also used. Cross section observations of the wire after tensile or creep-rupture tests have shown that the mechanism of rupture was mainly controlled by the void formation.

Abstract: In this work, the effect of the deformation, caused by cold wire drawing, on the microstructure and the texture of low carbon steel wire (0.06 wt % C) is examined. The combined influence of the deformation level and the recrystallization temperature on the development of new grains is studied for all wires. Isothermal tests of annealing allow the determination of the critical temperature of recrystallization estimated above 450°C. The temperature effect is studied below the eutectoid level, at 500°C, 600°C and 680°C. The appearance of a homogeneous recrystallization is noted over the section of the wire. The recrystallized grains keep the same orientation as the deformed grains. The expansion of time of annealing lead to recrystallization in the ferritic grains accompanied by a spheroidization of the lamellar pearlite. The kinetics of recrystallization and spheroidization are accelerated by increasing of annealing temperature and the deformation level. The experimental techniques used in this study are: the Scanning Electron Microscope (SEM), the Electron Back Scattered Diffraction (EBSD), the X-ray diffraction and Vickers microhardness.

Abstract: The effect of cold wire drawing on texture of industrial low carbon steel wire was investigated. On the other hand, the mechanism of recrystallization of drawn-wire was studied during different isothermal annealing below 723 °C. The structural evolution of wire was studied by optical microscopy, SEM, EBSD and X-Ray diffraction. From this study, a fiber texture was observed in deformed wire. However, a recrystallization reaction occurs after critical temperature during annealing.