Abstract: (300Å)Fe films were deposited, on MgO (001) single crystalline substrate with various buffer layer thickness tAg (Å) / (75Å) Cr. The magnetic properties of the Fe films were measured by magneto-optic Kerr effect (MOKE) technique. The MOKE measurements provided the tAg buffer layer thickness dependence of the hysteresis loops and the change of loop shapes with the surface roughness. It was found that the magnetization reversal process changed with the surface roughness. Magnetization rotation dominated the magnetization reversal for the smoothest films. As the films roughened, the domain-wall pinning set in, eventually dominating the magnetization reversal for the roughest films. Additionally, the magnetic uniaxial anisotropy in the Fe films disappeared as the roughness parameters increased. It was also found from MOKE that the surface roughness strongly affected the coercivity.
Abstract: This work purposes to investigate the microstructure and the mechanical behavior of dissimilar metals weld between 2205 duplex stainless steel (UNS 31803) and high strength low alloy steel API X52. The joining was produced by shielded metal arc welding process using two different filler metals, the duplex E2209 and austenitic E309 grade.The microstructures of the dissimilar welded joints have been investigated by optical microscopy, scanning electron microscopy and energy-dispersive spectroscopy (EDS). The EDS analysis performed at the API X52/weld metal interface showed an evident gradient of Cr and Ni between fusion and type II boundaries, where the highest hardness value was recorded.
Abstract: Rolling is a very common technique for shaping sheet metal. It aims to reduce the thickness of a metal sample to adapt it to the usual conditions of use in the industry. Nevertheless, this technique is not without modifying the mechanical and microstructural properties of the materials that can influence the mechanical strength of shaped parts. The purpose of the present investigation is to study the changes in microstructures and micro-hardness of Al-Mg-Si alloy with different rolling reduction in thickness and following artificial aging treatments at 175° C . We notice that the micro-hardness increases with the increasing of the deformation level . Reduction in thickness shows a change in microstructure and texture. Characterization methods used in this work is: Optical Microscopy (OM) and, Vickers microhardness.
Abstract: The purpose of this paper was to investigate the effect of Al2O3 and TiO2 nanoparticles contents on structural proporties, microhardness and corrosion resistance of Zn-Ni alloy coationg. Zn-Ni, Zn-Ni-Al2O3 and Zn-Ni-TiO2 composite coatings were electrodeposited on steel substrate by direct current in sulphate bath.The structure of the coatings was studied by X-ray diffration and by scaning electron miroscopy. The results showed the appearance of Ni5Zn21 phases and that the incrorporation of Al2O3 and TiO2 in the Zn-Ni coating refined the crystal grain size.The corrosion performance of coating in the 0.6M NaCl as a corrisive solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy EIS methods. It was found that the incorporation of nanoparticules in Zn-Ni alloy coating have better corrosion resistance and the values of Rct and Zw increase, while the values of Cdl decrease with increasing of nanoparticules.
Abstract: CrVN coatings between 10 and 26 at.-% V were prepared by PVD to investigate the effect of V on the properties of CrN system. The films were analysed using, DRX, X microanalysis, AFM SEM, scratch, tribometer and nanoindentation testers.The DRX spectrum shows the formation of (CrN-VN) phases and the examinations morphology show that the progressive change in the structure mode with adding V. The study of mechanical behavior shows degradation in the hardness and elastic modulus. On the other hand, the Cr-V-N film has a good wear resistance which remains lower than that of CrN film. Detachment of the Cr-V-N layer is observed at the all scratch trace while the CrN film exhibits best adhesion performance.
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.
Abstract: In this work, the microstructural evolution and the mechanical properties of WC-Co / AISI 1020 steel brazed joint obtained by oxyacetylene and Tungsten Inert Gas (TIG) brazing process are investigated. The maximum peak temperature induced by TIG process and the introduction of a shielding gas cause a remarkable diffusion of Co and rearrangement of WC particles along the interface with the filler alloy. The Energy Dispersive Spectroscopy (EDS) analysis reveals that the inter-diffusion activity of elements across the interfaces especially Co and Ni is more important using TIG process compared to oxyacetylene process The mechanical behavior is carried out through micro-hardness measurements and toughness tests using Vickers Indentation fracture method on the WC-Co along the parallel line of the interface with the filler alloy. The results show that the brazed joint issued from TIG process becomes increasingly hard and brittle when approaching the WC-Co/braze interface and loses its toughness (7 MPa/m1/2 compared to 15 MPA/m1/2 for oxyacetylene process) with increasing the brazing temperature.
Abstract: In this work we discussed the modeling of the demixing curve in the liquid state in the Lead – Zinc binary system. We are interested to recalculate the free energies relating on Pb-Zn alloys for several temperatures based on the thermodynamic data collected in the bibliography. This calculation allows us to trace the curve of phase separation from a program after obtaining the mole fractions corresponding to the common tangent to the curve of the free energy with two minima at different temperatures. To do this, we used the Matlab 7.1 as the programming language and the Redlich-Kister polynomial as a mathematical model of development. The results obtained are very satisfactory by comparing them with those of the bibliography.
Abstract: The aim of this work is to study the influence of the E6010 and E8018-G fluxes on the chemical composition, microstructure, formation of inclusions and micro hardness in different passes (P1, P2 and P3) of X42 welded steel. The marketed chemical composition of used fluxes is: E6010 and E8018-G, which have a low carbon electrodes. The fusion zone microstructure consists of acicular ferrite. The fluxes (FA and FC) have the high TiO2 and SiO2 contents respectively. The high content of Ti and Si, was also detected in the melted zones (P1 ,P2 and P3). The MnO2 oxide proportion in the fluxes (E6010, and E8018-G) is constant (0.94-0.99). However, the Mn content increases in the melted zones (P3 and P1). The highest percentages of Si and Mn was detected in the outer and inner passes respectively of melted zone, relatively to the base metal. The variation of the elements mass concentrations (Mn, Cr, Si and Ti) shows a contradictory variation on the three points in the melted zone passes (P1 and P3). White and black non-metallic inclusions are observed regardless the used flux. The micro-hardness in the multi-pass melting zone with the fluxes (E6010 and E8018-G) varies according to the variation of the equivalent carbon in the different filler metals.