Applied Mechanics and Materials Vols. 496-500

Abstract: The abrasion-resistant cobalt-base alloy K-C20WN was prepared by centrifugal casting and the effects of centrifugal temperature and speed on the microstructures and the performances of the casting were researched. The results showed that the microstructures of the casting consist of the loose equiaxed crystal, the dense equiaxed crystal, and the columnar dendrite from outside to inside. The centrifugal pouring temperature and rotational speed affects the performances apparently. Low temperature and high rotational speed help to enhance comprehensive mechnical performances of the alloys. And the improvement mechanism was also discussed in this paper.

Abstract: The7A52 aluminum alloy of the 30mm thickness was welded by the friction stir welding. The structure and the mechanical property of the welded joint was researched by the optical microscope and SEM, etc. The results showed: the hardness distribution along the cross section weld zone is W shape, TMAZ/HAZ transition zone of the weld joint is the softening zone , The min micro-hardness occurs on the TMAZ/HAZ transition zone of the advancing side. The tensile strength of the weld is 85.8% of the base mental, and it fractured in the TMAZ/HAZ transition zone, and the fracture morphology is dimple morphology.

Abstract: A series of composites of the high photoactivity of {001} facets exposed BiOCl and grapheme sheets (GS) were synthesized via a one-step hydrothermal reaction. The obtained BiOCl/GS photocatalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy. The as-prepared BiOCl/GS photocatalyst showed enhanced photocatalytic activity for the degradation of methyl orange (MO) under UV and visible light (λ > 400 nm). The enhanced photocatalytic activity could be attributed to oxygen vacancies of the {001} facets of BiOCl/GS and the high migration efficiency of photo-induced electrons, which could suppress the charge recombination effectively.

Abstract: This manuscript presents the synthesis and characterization of ZnS crystallitic films on ITO conducting glass by a simple hydrothermal method, based on sulfuration conversion from Zn nanocrystallines which are synthesized by pulse-plating technology. X-ray diffraction (XRD), scanning electron microscopy (SEM) and equipped with Oxford 7538 (EDS) analyzer techniques were used to characterize the Zn nanocrystallines and the novel ZnS crystallitic films. The results showed that ZnS crystallitic films were wurtzite, uniform and compact. Furthermore, the existence of Zn nanocrystallines and the complexing agent 5-sulfosalicylate influenced the microsopic morphology of ZnS crystallitic films. The optical properties, band gap energy and the size of nanocrystals were studied by UV-vis spectrophotometer measurements. A photoluminescence (PL) study of the ZnS at room temperature (300 K) indicates a strong luminescence band at energy 5.3 eV.

Abstract: The accuracy of simulation result depends greatly on the implemented hardening law. An appropriate hardening model should be able to describe the coupling effects of the strain, strain rate and temperature on the flow stress of the material. Based on the stress-strain curves obtained from uniaxial tensile tests, two different types of hardening models (power law and saturation) are proposed to describe the flow stresses of an aluminum alloy AA5086 under different temperatures (20, 150 and 200°C) and tensile speeds (1, 10 and 100 mm·s^-1). The correlation results are compared to experimental data and the roles of the hardening models in predicting the material flow stress are compared and discussed.

Abstract: In this paper, the characteristics of shape memory alloy (SMA) valveless micro-pump and its work principles are introduced at first. Based on the flow property of diffusion and shrinkage elements, the theory analysis is developed for a valveless micropump, and the flow distribution and pressure variation curve are then achieved with Matlab. Meanwhile, the finite model of the valveless micropump is built by using the ANSYS/FLOTRAN CFD finite element software, and coupled-field simulation analysis is carried out. The effects of different geometry parameters of diffusion and shrinkage elements on the pump performance are simulated and analyzed. The results show the valveless micropump working principle is mainly based on the flow difference of diffusion and shrinkage elements and its output characteristics are related to the geometry parameters. These results are helpful to design the optimal valveless micropump.

Abstract: Acrylonitrile-butadiene-styrene (ABS) / polymethyl methacrylate (PMMA) with the addition of maleic anhydride grafted polystyrene (KT-5) and polyolefin elastomer (POE) were melt processed in a co-rotating twin-screw extruder. The effect of KT-5 and POE content on the mechanical properties of ABS/PMMA was investigated. Experiment results indicate that KT-5 can improve the tensile strength and the composites are toughened effectively as the addition of POE. According to Orthogonal tests, it demonstrates that POE ha a greater effect on the blends than KT-5, and there exist no obvious interactivity between the two components.

Abstract: Polymer blends of poly (acrylonitrile-butadiene-styrene)/poly (methyl methacrylate) with ethylene methacrylate copolymer (EMA) were injection molded, and the notch sensitivity of the bends were examined by Izod impact and tensile tests. Investigations revealed that the toughness of ABS/PMMA composites were greatly improved and appeared a linear increase with the addition of EMA. However, the blends also show strong notch sensitivity due to the EMA component but the EMA content seems not a factor responsible for it. Tensile tests of the blends revealed that notches in any depth have great detrimental effects on the elongation at break of the materials, which is not consistent with the calculated notch sensitivity factor (k_S) data.

Abstract: Ethylene methacrylate (EMA) copolymer toughened acrylonitrile-butadiene-styrene (ABS)/polymethyl methacrylate (PMMA) were prepared in a co-rotating twin-screw extruder. The effect of EMA on mechanical properties and surface gloss of ABS/PMMA blends was investigated. Experiment results show that the toughness of ABS/PMMA is improved effectively with the incorporation of EMA, while the tensile strength and glossiness decrease slightly. ABS/PMMA/EMA blends present optimum mechanical and luster properties when the content of EMA is 6wt%.

Abstract: The atmospheric corrosion behaviors of AZ80 magnesium alloy are investigated by exposure test in different testing sites. After four months exposure test, the corrosion morphologies and the component of the corrosion products were observed by the scanning electron microscopy (SEM) equipped with energy-dispersive analysis of X-ray (EDAX). The corrosion rates of AZ80 magnesium alloys were calculated by mass-loss. The results indicated that the corrosion resistance of AZ80 magnesium alloy in the sea environment is the worst. The corrosion degree of the back surface is worse than the front side. The corrosion products are mainly formed by carbonate, and contain small amount of chloride in most environments, while in Xishuangbanna and Jiangjin area contain a little sulfate.