Journal of advanced materials and processing
Volume:7 Issue: 1, Winter 2019

In this work, Zn-Co-Mo coatings were electrodeposited on mild steel substrate from a citrate solution at current densities of 5, 7.5 and 10 mA.cm-2 and pH values of 4.5, 5, and 5.5. The coated samples were studied by scanning electron microscope and potentiodynamic polarization. The corrosion behavior of the coatings was related to the molybdenum content and formation of local anodes and cathodes. According to the results, a distinct range of current and pH was recognized to provide high quality and corrosion resistant coatings. The percentage of molybdenum as an alloying element plays an important role in the improvement of the corrosion properties of the coating. The formed coating at pH of 5.5 with 13 wt. % Mo showed the lowest corrosion current density with a value of 0.5 µA.cm-2.The molybdenum coating also showed a passive-like behavior in the anodic region due to the presence of molybdenum in the coating composition.

The microstructure and mechanical properties of a centrifugally Cast G-NiCrTi28W heat resistant alloy and effects of the elements migration from matrix phase to grain boundary have been stated and the effects of microstructure and composition changes on the life of reformer tubes from a direct reduction iron plant have been assessed. For this purpose, one sample from the as-cast tubes, and one from the aged tubes at 1100 °C for about 8 years, were used. Scanning electron microscopy (SEM) images and energy dispersive spectroscopy (EDS) analysis of two tubes were done. In as-cast tubes, the Cr7C3 primary chromium carbides and niobium-tungsten carbides were identified. Aging promoted the occurrence of different phenomena such as the transformation of Cr7C3 primary carbides to Cr23C6 secondary carbides, and the transformation of niobium-tungsten carbide to the M6C tungsten carbides. It was found that aging promoted the reduction in tensile strength from 580 MPa to 100 MPa and the increase in elongation from around 6% to around 30%. According to the results of the creep test at 960 °C and 52 MPa, no rupture occurs on the as-cast reformer tube during the test time.

In this paper, Forming Limit curves (FLCs) of AA3105 aluminum alloy sheet were obtained at four different temperatures using the Nakazima test. A novel approach based on the Nakazima test was applied to fabricate the experimental setup for determining forming limit diagrams (FLDs) at elevated temperatures. First, the Nakazima-die-set was manufactured, and a thermal system was prepared for increasing sheet and die’s temperature; then AA3105 samples were tested at four different temperatures experimentally. Moreover, the ABAQUS finite element software was employed. Three different criterions including the 2nd order of derivatives for major strain, equivalent plastic strain, and thickness strain were applied to estimate the onset of localized necking. The numerical results were verified by experiment. Both the experimental and finite element method results illustrated that the level of the forming limit diagram for the aluminum sheets improved by increasing its temperature. The forming limit improvement was not equal in every strain paths.

Fe3O4 nanoparticles were prepared solvothermally and then covered with boehmite shell via hydrothermal assisted sol-gel processing of aluminum 2-propoxide. Then the hydroxyl covered outer surface of the boehmite shell was covalently functionalized with 3-(tri-methoxysilyl) propylamine and the terminal amine groups converted to imine by refluxing with 2-hydroxybenzaldehyde. Then it was used to support bis-acetylacetonato-di-oxo-molybdenum (VI). The supported catalyst was characterized by Fourier transform Infrared spectroscopy, elemental analysis, inductive coupled plasma and transmission electron microscopy analysis and it was applied in the epoxidation of cis-cyclooctene. The catalytic procedure was optimized for different parameters such as solvent, oxidant, and temperature. The reaction progress was investigated by gas-liquid chromatography analysis. The used catalyst was simply recovered from the solution by applying a magnet and recycling experiments revealed that this heterogeneous nano-catalyst could be repeatedly applied for the epoxidation of cis-cyclooctene. The optimized conditions were also used for the epoxidation of some other alkenes successfully.

The presence of quartz particle size (> 45 µm) has a deleterious effect on the properties of porcelain tiles. The effect is caused by many factors including microstructure (pore) evolution after sintering. This study aims at investigating the effect of quartz particle size (QPS) on sintering behavior and flexural strength of porcelain tiles made from raw materials in Uganda. The samples were pressed at 40 MPa, fired from 1150-1350 0C at a firing rate of 60 0C/min, and soaked for 1 hour. The sintering behavior was analyzed based on linear shrinkage, water absorption and Scanning Electron Microscope (SEM) micrographs. Phase identification was carried out using X-ray diffraction method. The optimal sintering temperature of 1300 0C was established, and firing to 1350 0C resulted in bloating as observed by SEM. Samples containing fine and medium QPS had a value of 0.47 % and 0.90 % water absorption respectively at optimum temperature. Pressed tiles with and those > water absorption are classified as Group BIa and BIb respectively (ISO 13006), suitable for use as floor or wall tiles. Also, the average flexural strength of 33, 18 and 8 MPa was exhibited by samples with fine, medium and coarse QPS respectively. The results indicate that only samples with fine and medium QPS satisfy the requirement MPa and > 12 MPa for floor and wall tiles respectively (ISO 13006).

The use of lasers is being considered as a modern method for forming process in recent years. This method has been used in various industries, such as aerospace, marine and oil industry. Extensive research has been done in the field of modeling and optimization of direct paths parameters with process of laser forming. Although forming in circular paths can be used for producing complex parts, due to some technical reasons, it is considered less. The main purpose of this paper is to detect the proper estimation model and obtain optimal variables conditions for complete circular paths in perforated circular parts by means of genetic algorithms. In this process the outer edges are fixed and the inner edges are being formed by laser. At first, the finite element simulation model is studied then the estimation model has been discussed, after that multi-objective functions have been examined with the least error and energy. Furthermore, the optimization results of the internal hole diameters are reported and analyzed in terms of Pareto charts. In conclusion, optimum forming conditions have been reported in terms of accuracy and energy for different diameters of holes. This study shows with acceptable increasing in the error rate, the required energy could be reduced. Also, increasing in the diameter of inside hole cause to increase energy and decrease of accuracy.

Although microbiologically induced corrosion (MIC) is well known by design engineers and manufacturers, most current marine devices continue to be impressed by MIC. This phenomenon originates from colonization of anaerobic microorganisms on metal surface, and subsequently increases the corrosion rate. An investigation was made to defeat MIC by means of applying a TiO2 thin film on metal surface. 316L stainless steel and sol-gel dipping technique were chosen as the base metal and application method, respectively. The depositing variables including PEG adding amount, pH of the sol, calcination temperature (T), and dipping cycles number, were analyze by Taguchi statistical model to determine their influences on response parameters: bactericidal efficiency, current corrosion density (icorr), crystallinity, crystallite size, and surface roughness (Ra). A parameter termed Aim was defined to comprise all the response parameters. Taguchi Predicted conditions to achieve the highest Aim value. For this aim, PEG content, pH, T, and dipping cycles should be equal to 1 g per 100 mL of sol, 11, 600 °C, and 2 cycles, respectively. These conditions were applied to prepare the optimized sample. Careful evaluation of this sample approved the Taguchi prediction and the highest Aim value was observed.