Advanced Materials Research Vols. 463-464

Abstract: In order to study welding performances of duplex stainless steel, gas tungsten arc welding (GTAW) was adopted to butt-weld the S31803 tube whose wall thickness is 18.26mm. Metallographic structures of the weld, base metal and heat affected zone (HAZ) were also analyzed. Crevice corrosion resistance of the GTAW joint in 6%FeC13 + 0.05mol/L HCl solution in different temperatures had been tested according to ASTM G48. The results showed that with rising of temperature the average rate of crevice corrosion increased but the growth of corrosion rate slowed when the temperature reached a certain degree. There was corrosion groove in submarginal area of the crevice and the area near HAZ of the groove was much deeper. The results provided a reference to welding technology of S31803 DSS and also provided experiment resources for research on welding of the DSS.

Abstract: In the present study, 20 Wt. % ZrO₂-Al₂O₃-17 wt.% TiO₂ powders were sprayed using a plasma-spray technique after a NiAl bond layer was deposited on plain carbon steel substrate. The produced coatings were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) including energy-dispersive spectroscopy (EDS). The tribological properties of coatings against hard alloy ball were investigated by using a pin-on-disc tribo-meter under dry environments. The predominant wear mechanism of coating is fatigue.

Abstract: The way to determine the optimal solids content of TiO2 in DSSC working electrode was discussed. As a mathematical proof of the optimal conclusion extracting from the complex working mechanism of DSSCs and accidental factors, the equivalent circuit parameters of each curve are estimated corresponds to the equivalent circuit method first. And then, the trends in each parameter are analyzed. According to these trends, the optimal solids content of TiO2 are optimal identified

Abstract: In order to obtain the high dielectric constant and low loss materials by using the two main methods for synergy, the 3-phases TiO2/(PVDF+Fe₃O₄) composites with the fixed Fe3O4 fraction have been prepared by using a simple blending and hot-molding technique. The dielectric measurement results show that no synergistic effect but a cancellation effect has been found here, corresponding to the decrease of dielectric constant and conductivity. The value of the relative dielectric constant dropped to the original level of polymer matrix. The reasons for the counter result are present here. It is helpful and reference for the proper choice for multiphase composite system.

Abstract: Average impact energy of 4145H steel and X new type drilling collar steel satisfied the standard of “SYT5144-2007 Drilling collar” and “API SPEC7”. With temperature getting down, impact energy of 4145H steel decreased, impact energy Cof X drilling collar steel is a lot higher than 4145H steel, crack propagation energy and crack propagation energy/impact energy ratio decreased. Lower temperature leads to higher crack propagation rate. The crack propagation energy of 4145H is lower than X drilling collar steel. The crack propagation energy/impact energy ratios of X drilling collar steel are at least 3% higher than 4145H for different temperature. In drilling, crack growth rate in X DC was slower than 4145H DC, crack growth rate was fast, and the DC was easy to fracture in low temperature

Abstract: The mechanical properties of aluminium alloy castings, such as EL%, YS and UTS, are controlled by the casting and heat treatment variables, alloy’s composition, and melt treatment. Despite the abundance of literature data, the large number of the controlling parameters has made it difficult to predict and model the mechanical properties by the conventional techniques. Another obstacle encountered when making such a prediction is the complex kinetics and interactions that exist among the many variables. The goal of this study was to develop Artificial Neural Network (ANN) and Multiple Regression models to predict the mechanical properties of A356 alloy from the processing variables. Several standard nonlinear regression and multi-layer ANN models were developed and trained using data from the literature and experimental results. Due to the complexity of A356’s solidification behaviour, the nonlinear regression produced results that were not as accurate as those produced by the ANN model. The results indicate that ANN is a suitable technique for predicting mechanical properties from alloy chemistry and processing variables.

Abstract: The present paper deals with the study of microstructure and wear characteristics of hot rolled beryl reinforced aluminium metal matrix composites (AMMCs). Al6061-beryl composites with 2, 6 and 10% of beryl were made using stir casting technique. The optical microstructure reveals the homogeneous dispersion of beryl particles in the matrix. The worn surfaces have been observed under SEM to understand the mechanism of wear. Hot rolled composites at 4500C possess higher hardness and lower specific wear rates under all loads and sliding distance studied in this investigation, when compared with cast composites.

Abstract: Surface treatment of water hyacinth fiber (WHF) was investigated as a mean of improving interfacial of WHF reinforced poly (lactic acid) (PLA) composites. Fiber was treated with sodium hydroxide 15% w/v at 85 °C for 3 h. The composite materials were processed using internal melt mixer and compression molding machine. The weight content of fibervaried from 5 to 25% w/w.The mechanical and thermal properties of pure PLA and composites were compared using universal testing machine, differential scanning calorimetry (DSC) and thermogravimetricanalysis (TGA).The best mechanical properties of composite were achieved at fiber mass content of 20% w/w in this study, which showed an increase oftensile modulus by 21.6% compared to those of pure PLA. The high tensile modulus but low elongation at break indicates that this material exhibits brittle behavior. The results of TGA andDSC experiments indicated that the addition of fiber enhanced the thermal stability of the composites and WHF can act as a nucleating agent for PLA crystallites. The morphology, evaluated by scanning electron microscopy (SEM), indicated that a uniform dispersion of fiber in the PLA matrix existed. Alkali treatment of fiber increased the interfacial bonding strength and the wettability of the fiber by PLA leading to the enhancement in mechanical properties of the composites.

Abstract: Ba0.9Sr0.1TiO3 ferroelectric ceramics with dopants of La₂O₃(0, 0.1, 0.1, 0.2 mol%) and Nb₂O₅(0, 0, 0.1, 0.1 mol%) were prepared in solid state process. The double donor substitutions can weaken lattice size effect by the two different size substitutions. XRD method was used to analyze the crystal structure of the samples, and SEM was used to observe the topography, grain’s size and ceramics density. The results of dielectric-frequency relation indicate that when the contents of La₂O₃ and Nb₂O₅ are both 0.10 mol%, the permittivity can reach to 150 000, and the dielectric loss keeps only 0.118. When the total donor content is lower than 0.40 mol%, compensation effect is dominated by electrons. The giant permittivity is attributed to electrons inside grain and insulated grain boundary. When the dopant content is higher than 0.40 mol%, the compensation effect is dominated by the host cation vacancies. The permittivity decreases rapidly with the increase of the donor concentration.

Abstract: Underwater blast injury is a common war injury during combat around islands or fighting for beachhead, and is also ordinary in underwater engineering construction blast. Adding an extra underwater blast wave protection layer and Integration with life jacket is a reasonable protection measure. Four different low mass density closed cell polyurethane foams used in life jacket have been tested by quasi-static material testing machine, and the dynamic mechanical behavior at strain rates of 10-3～10-1s-1 has been analyzed. The yield strength has been tested with Split Hopkinson Pressure Bar. Experimental results show that the compressive performance of the polyurethane foam is sensitive to the strain rates. The polyurethane foams’ yield strength shows rising trend along with strain rates increase. Under the condition of the plateau yield strength below human’s allowable pressure, the energy absorption performance of the polyurethane foams has been analyzed and in contrast.