- Ei，ESCI收录期刊
- 中国科学引文数据库(CSCD)核心期刊
- 中文核心期刊
- 文摘与引文数据库(Scopus)
- 剑桥科学文摘(CSA)
Plastic deformed layers of as-cast single crystal(SX) nickel-based superalloy blade surface were formed by using three kinds of surface treatment process(grit blasting, abrasive belt polishing, felt wheel polishing). The deformed layers were electrolytic etched by using a specially designed electrolytic device, followed by standard heat treatment. Surface-treated deformed layers of single crystal superalloy blade and its electro-etched microstructures were investigated. The results show that the depths of deformed layers on as-cast SX blade surface are respectively about 6, 3.5μm and 2μm by using three kinds of surface treatment process. The microcrack fracture characteristics exist around the surface deformed layers by grit blasting and abrasive belt polishing. Large amounts of deformed γ' structure is existed in the electro-etched transition region of surface deformed layers, and the residual plastic deformation of three kinds of surface treatment process decreases successively in electro-etched transition region. Plastic deformation is not found in totally electro-etched region. After standard heat treatment, sag characteristics and recrystallized grains exist in non electro-etched region of deformed layers, but neither obvious pits nor recrystallized grains are found in totally electro-etched region.
Using bismuth nitrate and ammonium tungstate as raw materials, mesoporous bismuth tungstates(Bi2WO6) were synthesized by a facile hydrothermal process. The phase composition, structure, optical absorption properties and morphology of Bi2WO6 photocatalyst were characterized by XRD, UV-Vis, FE-SEM and TEM, the forming mechanism of three-dimensional spherical mesoporous Bi2WO6 was speculated. The effect of solution's pH value and common inorganic ions in the natural water on the mesoporous Bi2WO6 photocatalytic activity was also studied. The experimental result of methyl-blue(MB) photocatalytic degradation show that the mesoporous Bi2WO6 exhibits better photocatalytic activity in the strong acidic solution. Furthermore, investigation reveals that common inorganic ions have obvious influence on the photocatalytic degradation of methyl-blue. Cation, such as NH4+ and Fe3+, and anion, such as Cl-, Br- and I-, can obviously promote the degradation of methyl-blue. Cu2+ and NO2- have nearly no effect on it. While, Fe2+ can clearly inhibit the degradation of methyl-blue.
The microstructure and corrosion properties of AM60-2%RE magnesium alloys with the addition of trace Zn were investigated by X-ray diffractometer(XRD), scanning electron microscope(SEM), polarization curve and electrochemical impedance spectroscopy. The results show that the Zn element added is mainly solution distributed in the matrix, without forming new intermediate phase with the other elements; while, the amount of phase Al11RE3 increases obviously, and is distributed intermittently on the grain boundary. With the increase of Zn content, the corrosion current density of the alloys is reduced, the charge transfer resistance increases and the compactness of corrosion products is improved, leading to obviously improved corrosion resistance. The corrosion rate is 0.405mg·cm-2·d-1 for the alloy with 0.8% Zn addition, which is lowered to 36% that of the alloy with 0.2% Zn addition.
The influence and mechanism of electric current pulse on the cast W6Mo5Cr4V2 high speed steel microstructure were studied. The changes of its composition and microstructure were observed by using optical microscopy, X-ray diffraction(XRD) and energy spectrum analysis(EDS). The results show that the microstructure of the cast HSS is mainly composed of MC, M2C and M7C3 eutectic carbides, martensite, austenite and pearlite. The carbides exhibit continuous network distribution along grain boundaries, and there are some herringbone-like eutectic carbides. After being treated by the electric current pulse, the carbides have no change, but appear differently, from the network carbide tending to fracture, and with obvious trend of isolation and spheroidizing, the herringbone-like eutectic carbides disappear, meanwhile, the content of the carbide decreases, the content of the alloy elements in the matrix increases, the hardness of the matrix is improved. Joule heat and electromagnetic force coupling physical effect are the main mechanism of these phenomena.
Zn-Al alloy composites reinforced with SiC particles were prepared by combining semi-solid mechanical stirring with ultrasonic vibration process. Interaction between SiC ceramic particles and liquid Zn-Al alloy with aid of ultrasonic vibration was investigated. The results show that ultrasonic vibration imposed on the Zn-based composites can cause high cavitation intensity in the liquid Zn-Al alloy which disrupts surface oxides on the Zn-Al alloy and gas films adsorbed on the particles, thereby allowing the Zn-Al alloy to wet the bare SiC ceramic particles surface and form a metallurgical bond. The interface between SiC particles and Zn-Al alloy is rather plane and clean with no voids. Which mean that a wet-type bonding interface forms between SiC particles and Zn-Al alloy under ultrasonic vibration.
The microstructure, mechanical properties and second phase precipitation behavior of a high Nb microalloying steel at different coiling temperatures of 400, 450℃ and 500℃ were investigated by scanning electron microscope, experimental machine of mechanical property testing and transmission electron microscope. The results show that, with the decrease of the coiling temperature, during the coiling process, the bainite microstructures transformed from super-cooled austenite are granular bainite, lath bainitic ferrite plus granular bainite, and lath bainitic ferrite, respectively. At different coiling temperatures, the second phase precipitates from the experimental steel are mainly(Nb, Mo) C which randomly precipitate on dislocation lines, and interphase precipitates are observed in some areas. As the coiling temperature decreases, the precipitation decreases, the average particle size increases. With the increase of the coiling temperature, the tensile strength and yield strength are improved, while the low temperature impact toughness decreases. The strength being improved is due to the precipitation strengthening as with a large number of(Nb, Mo) C particles with size less than 10nm.
Low-molecular weight polyacrylic acid(PAA) was used for blending modified poly-propylene(PP) to prepare polyacrylic acid/polypropylene composite plastics(PAA-PP)with scale inhibiting effect. By using the EDTA complex metric titration method, the scale inhibition performance of PAA-PP composite plastics was investigated. The surface morphology of PAA-PP was observed by scanning electron microscopy(SEM) and the CaCO3 fouling sample was analysized.The results show that the PAA-PP composite plastics has good scale inhibiting effect, when the content of PAA is 1.55%, the high scale inhibition rate can reach 92.77%;The results show that the calcium carbonate scale grains become smaller and not easy to have nucleation growth and grow regularly and adhere on the surface of the PAA-PP composite plastics.
The nitrogen-doped carbon nanotubes were synthesized by chemical vapour deposition, and then added into aluminium matrix to get carbon nanotubes/aluminum matrix composites. The structure and doping pattern of the nitrogen-doped carbon nanotubes were characterized by TEM and XPS, and also research and analysis were carried out on the mechanical and electrical properties of the aluminium-based composites. The results show that carbon nanotubes exhibit a periodic multilayer bamboo-like structure and nitrogen atoms are doped successfully. Compared with pure carbon nanotubes, the nitrogen-doped carbon nanotubes/aluminium matrix composite has a higher tensile strength and electrical conductivity. The incorporation of nitrogen atoms improves the dispersion and wetting characteristic of carbon nanotubes, enhances its efficiency of electron transfer, and thus benefits its applications in metal matrix composites.
The fiber trajectories for geodesically over wound toroidal pressure vessels and related stable winding conditions were derived based on differential geometry. The obtained winding trajectories were also simulated for several conventionally-used partitions. The optimal initial winding angle and minimally required total layer number were determined for titanium-lined filament wound toroidal pressure vessels. The load-carrying capacities of torodal pressure vessels with and without hoop reinforcing layers were respectively calculated and compared to each other. The results show that the designed geodesic patterns are accurate and reliable, and satisfy the windability of toroids. The obtained optimal winding parameters simultaneously meet the windability and improve the vessel performance, and thus the fiber strength can be fully utilized. The results also indicate that the addition of hoop reinforcing layers leads to 14% raise in the burst pressure of the toroidal vessel and 24.8% increase in the yield strength of the titanium liner. Therefore, the load-carrying capacities can be significantly improved by adding hoop reinforcement. The hydrostatic test results show that the deformation and the burst pressure predicted using the present method & model agree well with the experimental data.
In order to improve the dispersibility of ZnO nanoparticles in the organic phase, isopropyl tri(dioctyl pyrophosphate acyloxy) titanate(NDZ201) was used to modify ZnO nanoparticles. Scanning electron microscopy(SEM) was used to characterize the morphology of the nano-ZnO after modification, Fourier transform infrared spectrometer(FTIR spectrometer) was used for investigating the chemical structure of the modified nano-ZnO, and ultraviolet-visible spectrophotometer(UV-Vis) and contact angle tester(CA) were used in detecting the properties of the modified nano-ZnO. The results show that ZnO nanoparticles are modified successfully by NDZ201, the dispersibility of which is improved after modification. What's more, the hydrophobicity of the particle is improved significantly and the lipophilic degree together with UV absorption increase. Afterwards, NDZ201 modified ZnO nanoparticles are introduced into hydrogenated castor oil to prepare nano-ZnO/modified hydrogenated castor oil composites, and then the composites are applied to leather fiber. It is found that the latex particles of nano-ZnO/modified hydrogenated castor oil composites are spherical. ZnO nanoparticles and modified hydrogenated castor oil exhibit synergistic effect in UV-shielding. Moreover, the anti-yellowing property of leather sample treated with the composites is superior to that of which treated with the pure modified hydrogenated castor oil under the same test condition.
Corrosion kinetics curves of Super304H coated with Na2SO4-25%NaCl at 650℃ and 750℃ in the air were investigated by applying weight analysis method. The corrosion product, cross-section appearance and elements distribution were analyzed by XRD, SEM equipped with EDS, and EPMA. The results show that the corrosion kinetics curves at 650℃ and 750℃are in parabolic trend. A two-layered complex oxide film with the outer Fe rich oxide layer containing CuFe2O4 and inner Cr2O3rich layer and the poor Cr, rich Ni corrosion affected zone containing voids; Increasing the temperature or prolonging the corrosion time can result in the separation or even spalling of oxide film from the base alloy, and porosity density increases in the corrosion affected zone, cracks propagate to the base metal. Analysis shows that the selective oxidation occurs at the early corrosion stage and forms multi-layer oxide film; the molten salts destroy the integrity of the oxide film and accelerate the interaction among oxidation, chlorination and sulfuration during the corrosion processing, which results in the severe internal oxidation and sulfuration.
On the twin-disc MMS-2A rolling contact tester, the damage behavior of the friction pair of rail(U71MnK)/wheel(ER8) materials used for Beijing-shanghai high speed railway was investigated under different slip rates with the normal force of 120N(to simulate the axle mass of 16t) and the rotating speed of 500r/min. The morphology of wear surfaces, its cross-section profiles and the chemical elements on the wear surface under different slip rates were analyzed by the scanning electron microscope and the energy dispersive X-ray detector. The results show that the changing trend of the friction coefficient under different slip rates can reflect the materials damage process; the hardening degree of the rail/wheel materials goes up with the increasing of the slip rate; the damage mechanism is different under different slip rates; under the condition of quasi rolling contact, the slight damage of the wheel/rail materials can be observed and the wear mechanisms are mainly the oxidation wear and the local spalling. As the slip rate increases, the dominated wear mechanism of the wheel/rail materials is the fatigue wear accompanied by the oxidation wear and abrasive wear, furthermore, the degree of the abrasive wear also increases with the slip rate.
The influence of hygrothermal environment on flexural property of woven carbon fiber epoxy resin composite was investigated via three point flexural test under different temperatures. Moisture absorption, fracture morphology, dynamic mechanical property and load curve were analyzed. The results show that the moisture absorption of woven carbon fiber epoxy resin composite is just about 0.88%. The influence of hygrothermal environment on flexural strength of composites is greater than flexural modulus. The fracture mode of dry samples is all brittle fracture;Wet samples are not fracture only at high temperature. The glass transition temperature(DMA Tg)of composite after moisture absorption is 125℃, which is 16℃ lower than that of dry. The load and displacement curves is linear at the early stages of the flexural deformation, the dry samples have a little fluctuation before reach the load peak. Wet samples have obvious buckling or plastic deformation, and the phenomenon more obvious with the increase of temperature.
Through rotating bending fatigue test carried out in air condition, the fatigue limit of DAGH4169 superalloy with three different stress concentration sensitivity coefficients(Kt=1, Kt=3 and Kt=4) at room temperature and at 650℃ was studied. The research results indicate that the DAGH4169 superalloy is severely sensitive to the stress concentration both at room temperature and at 650℃. When it is at 650℃, the fatigue limit of DAGH4169 superalloy with stress concentration sensitivity coefficient Kt=4 decreases by 68% compared with Kt=1, and the fatigue limit decreases by 66% at room temperature. Meanwhile, the fatigue limit of the DAGH4169 superalloy is obviously lower at room temperature than at 650℃. When Kt=1, the fatigue limit at room temperature decreases by 32% compared with at 650℃, and the fatigue limit decreases by 30%, when Kt=3, and the fatigue limit decreases by 28%, when Kt=4.
CaSO4 whisker reinforced resin-based composite friction materials(sample A) were prepared by thermo-compression process, and a commercial brake material(sample B) was selected as a reference. The influence of braking frequency on the tribological performance of samples was investigated by CHASE tester. The SEM and EDAX were used to observe the wear surface morphology and the composition of the surface of films respectively, and the influence mechanism of braking frequency on wear mechanism of samples was analyzed. The results show that CaSO4 whisker has played a significant toughening and strengthening effects on sample A, the average friction coefficient of sample A always maintains at a high level of around 0.48 and exhibits stable and reliable braking performance with the change of braking frequency. Moreover, the damage degree of dual disc is lighter, and the main wear mechanism is abrasive wear. While the friction coefficient of sample B decreases firstly and then increases, and shows sensitive to the change of braking velocity, as well as its main wear mechanism is adhesive wear and oxidation wear. The friction surface temperature and mass wear rate of samples are increased with increasing of braking frequency, but both materials show good wear resistance when the braking frequency less than 35 times.
The phase composition, morphology, element distribution and corrosion resistance of surface insulation coating on the oriented silicon steel were investigated in detail using X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and electrochemical workstation, respectively. The results show that the structure of the insulation coating is double compound layer. The bottom layer is Mg2SiO4 phase with 0.8μm thickness. The top layer is AlPO4 phase with 1.4μm thickness. There is a diffusion area with 0.4~0.6μm thick at the junction of two layers. In comparison to the sample coated single Mg2SiO4 layer, the sample coated double compound layer exhibits higher corrosion potential, higher polarization resistance and lower corrosion current density, thus leading to better corrosion resistance. With the increase of immersion time, the corrosion solution gradually permeates into the insulation coating and reaches the silicon steel substrate, and then reacts with the substrate. The corrosion process can be divided into three stages.
The bending fatigue fracture properties of G105 drill pipe body materials and the influence of H2S corrosion and notch on the specimen bending fatigue performance were studied using the domestic PQ-6 type rotating bending fatigue testing machine. The fracture surfaces of smooth specimens, notched specimens and H2S corroded specimens were analyzed using metallographic microscope and scanning electron microscope. The results show that under the stress of smooth specimens' ultimate fatigue loading, the fatigue life of specimens corroded by H2S is same as that of notched specimens, declining from 106 to 104. The high stress concentration effect of notch can accelerate the process of fatigue crack nucleation in the notch specimen. The main role of H2S corrosion is that the hydrogen atoms will gather together at the inner defects, which will decrease the fatigue life. H2S corrosion and notch both can accelerate the propagation speed of the fatigue cracks. The main reason for the fatigue fracture of material is that the specimens under action of alternating stress engender slip, finally resulting in dislocation stacking.
Three kinds of Fe-Cu alloys Fe80Cu20, Fe60Cu40, Fe50Cu20 were prepared respectively by spray casting and melt-spinning way. The microstructure, thermodynamics properties of Fe-Cu alloys during phase separation process were observed and analyzed through SEM, XRD and DSC measurement. The results show that three different Fe-Cu alloys have different levels of phase separation, the initial temperature of liquid-liquid(L-L) phase separation increases with increasing Cu content, meanwhile, phase separation phenomenon is more obvious. The grain size of Fe-rich phase and the volume fraction in Fe80Cu20 decreases with increasing degree of undercooling, while the crystal lattice constant of both Fe and Cu phases increases gradually. The increasing degree of undercooling improves the solid solubility of phase separation. The Fe-rich balls formed due to secondary L-L phase separation in Cu-rich phase are also observed in Fe50Cu50 and Fe60Cu40 alloys. The growth of the Fe-rich balls is the coagulation process of the two adjacent balls by the migration of smaller balls moving towards the bigger ones to reduce of interfacial energy. The rapid solidification process of Fe-Cu alloy with miscibility gap has been revealed.
After introducing the principle and classification of 3D printing, methods for metal forming using 3D printing were reviewed in details, including electron beam melting(EBM), selective laser melting(SLM), laser direct melting deposition(LDMD). The application fields of metal 3D printing and research status overseas and domestic were also discussed in this paper. At last, based on the current development of metal 3D printing, this paper summarized the key issues that should be solved, which include the quality of powders, the usage of 3D printing equipments, nondestructive testing for 3D printing components, the failure analysis and prediction of lifecycles for 3D printing components. The standards of nondestructive testing for 3D printing components should be established and the database of comprehensive mechanical properties for 3D printing materials should be built.
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