Advanced Materials Research Vols. 139-141

Abstract: Galvanized Q345 steel specimens were accelerating corroded with accelerating environment spectrum for equivalent 1, 3, 4 and 5 years, and then its corrosion behavior was studied based on macro corrosion appearances, micro corrosion appearances, weight loss, pits depth and fatigue strength. The results show that, i because the zinc coating can protect the matrix metal from corroding, the corrosion resistance of galvanized Q345 is much better than Q345; ii between the 1st year and the 4th year, pitting corrosion is dominative, and after the 4th year, the corrosion form transforms from pitting corrosion to uniform corrosion; iii after corrosion for 5 years, the zinc coating was not destroyed completely, and with the turning point of the 4th year, the corrosion rate of the zinc coating becomes higher firstly and then gets lower, which agrees with previous study.

Abstract: The corrosion depth, corrosion area, corrosion pit volume and area of LY12CZ aluminum alloy with different corrosion time were obtained from accelerated corrosion experiment. Four distribution models such as normal, Gumbel, Logistic and double parameter Weibull were used to test their distributions. It can found that the corrosion depth and corrosion area obey Gumbel distribution and the area and volume of corrosion pits obey double parameter Weibull distribution; Choose ten variables as the parameters of influence corrosion fatigue life, through grey relational analyze we can found that the deepest corrosion depth is the biggest influence gene of corrosion fatigue life, and the corrosion grade is an important influence gene almost equal to the deepest depth because it considered the influence of corrosion area and corrosion depth, so we can use it as an parameter to evaluate the calendar life of corrosion conditions.

Abstract: In order to study the quality of TA2 sheet in laser bending deforming area, SM2000 CO2 laser of 2.5kW is used to irradiate 0.6 mm thick TA2 sheet, and the change of the surface properties of the TA2 plate after laser forming was investigated with the X-ray stress analysis instrument (type: X-350A), Digital Micro hardness Tester HVS-1000 and Scanning Electric Mirror (SEM ) respectively. The result of the experiment indicates: the roughness of the forming sheet after bending will increase. The roughness of deforming area increases dramatically. The further the surface from the bending area, the less roughness in the bending area, residual stress changes regularly. The organization of the deforming area is changed, and the branch crystal forms on the surface of the forming sheet. The diameter is about 0.5μm. The branch crystal grows upward.

Abstract: The thermoelectric potential of the cemented carbide is the one of the major properties of material. The analysis and the test about the relationship between the wear and the thermoelectric potential of YT715 cemented carbide inserts have been finished in this paper. The influence rules and the influence extent of thermoelectric potential to the wear have been emphasized. The thermoelectric potential E and the wear value VB of YT715 cemented carbide inserts are very closely relationship, the bigger thermoelectric potential E, the more serious wear. Then the new method of forecasting the life of cemented carbide has been also discussed.

Abstract: Copper matrix composites with 3wt% diamond particles were fabricated by powder metallurgy method. Sliding wear behavior of the copper-diamond composites was carried out by using a pin-on-disk wear tester under dry sliding conditions at a constant sliding speed of 100 m/s. The results showed that the wear rate of the composites was significantly lower than that of pure copper. The addition of diamond particles can markedly increase hardness and wear resistance of the copper-diamond composites. For determination of the wear mechanisms of the copper-diamond composites, a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) was employed to observe the microstructure and analyze the chemical compositions of the worn surface. It is found that the main wear mechanisms of the sintered copper-diamond composites were abrasive wear and adhesive wear.

Abstract: The primary objective of this study is to develop equations of the bond stress and relative slippage between fiber-reinforced polymer (FRP) bars and concrete exposed to different temperature ranging from 20°C to 190°C. Equations were established through theoretical analysis and simulation of the bond-slip constitutive relationship between FRP bars and concrete. According to the expressions, the variations of the bond stress and relative slippage between the two diffident materials can be evaluated at different locations. This paper made the analysis based on the theory of elasticity, using a bilinear model. An example to compare the results between experiment and theory had been proposed. It is indicated that the theoretical analysis here is in good agreement with the experimental data in related literature. The results can be applied to fire resistance design of FRP reinforced concrete structures.

Abstract: This paper mainly discusses the technique of using quenching at 1000°C and tempering at 650°C for 2 hours to replace the heat treatment process of quenching at 1225°C and tempering at 560°C for 1 hour for three times.Due to the old heat treatment process is traditional multifarious waste energy and relatively backward.The experiment results prove that after the new treatment using the W6Mo5Cr4V2 high-speed steel to make cutting tools such as cutters, drill, taps and so on. It aslo achieves better abrasion resistance and ductility. This meeting the objective of improving the wear resistance, toughness, lifespan enhancement and energy conservation.It opens up a new way of simple and energy saving for W6Mo5Cr4V2 high-speed steel heat treatment process.The material of W6Mo5Cr4V2 high-speed steel has certain value to research.

Abstract: The morphology of the coir fiber by alkali treatment and untreated was analyzed by scanning electron microscope (SEM). The main component of wax layer on coir fiber surface and the mechanical performance of coir fiber/line low density polyethylene (LLDPE) bio-composites were studied. The flexural and impact strength of the composites after alkali treatment for the fibers were lower obviously than that of the composites without treatment. The result of Infrared Spectrumetry-Fouorier Transform (FTIR) shows that fatty acid and waxy material on the surface of the coir fiber were disposed of by alkali solution. The fatty acid and waxy material are compatible with non-polar LLDPE matrix. The compatibility between the coir and matrix was reduced obviously with loss of them. Therefore, the alkali treatment weakens significantly the compatibility between the coir and LLDPE, and this is a main reason that the mechanical performance of the composites was markedly declined.

Abstract: Weldability analysis, metallographic experiments and mechanical property experiments were carried out on weld joint between B610CF and 16MnR steel using shielded metal arc welding method and mixed active-gas arc welding method. Weldability analysis shows that the weld joint has some tendency to cold crack, and preheat is needed before welding. Metallographic results show that there are ferrite and bainite in weld metal, and in heat-affected zone of B610CF side there are ferrite and bainite, on which there is much dispersed slight Fe3C, and in heat-affected zone of 16MnR side there are ferrite, pearlite. There is no quenching microstructure resulting in crack in weld joint. From mechanical property results, it can be concluded that the weld joints have excellent impact toughness at low temperature and the tensile strength and plasticity of weld joints is matched to the ones of 16MnR steel. So the welding parameters in this paper are appropriate to get qualified weld joints.

Abstract: An average creep rate conversion model based on Schlottner-Seeley creep assessment procedure and creep damage equation has been developed by considering the relationship that two stages of stress relaxation are corresponding to the first and the second creep stage respectively and the effect of these two kinds of creep rate on relaxation, and stress relaxation is creep at various stresses. And an incremental calculation prediction methodology of stress relaxation performance was established. The predicted results are compared with the data of stress relaxation tests conducted on bolting steel 1Cr10NiMoW2VNbN used in ultra-supercritical turbines. Validation results indicate that the developed model has led to better consistent results with the measured data and thus can be recommended in stress relaxation behavior prediction of high temperature materials.