- 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)
The latest research progresses on Fe-based amorphous coatings were reviewed. The typical alloy system and the classification of Fe-based amorphous coatings were clarified. The status, progress and development of the Fe-based amorphous coatings prepared by thermal spray processing and laser cladding process were discussed. The main mechanical properties and potential applications of the Fe-based amorphous coatings were also described. Furthermore, based on the main problems mentioned above, the future development of the Fe-based amorphous coatings was discussed, including the exploitation preparation technologies of high amorphous content of the Fe-based coatings, the development of the low cost and high performance Fe-based coating alloys system, the broadening application of Fe-based amorphous coatings, and so on.
The application and new development trend of metal additive manufacture technique were introduced, as well as the characteristic and NDT difficulty of metal additive manufacture products. The research progress of NDT was analyzed in emphasis, including the classification of metal additive manufacture technique, the characteristics of defect and microstructure, the influence of defects on mechanical properties, the latest development of NDT methods and standards. Based on that, the key issues that will be focused were summarized at last, that is the application of new NDT methods, on-line monitoring technology, numerical simulation, measurement and characterization of stress, as well as the establishment and development of NDT standards.
Pathogenic microorganism is a serious threat to human health. As a novel kind of antibacterial materials, silver nanoparticles involving their preparation approaches and applications are of great research interest in the field of nanomaterials. This review summarized a summary of synthesis methods of silver nanoparticles, including polysaccharide, Tollens, irradiation, biological and polyoxometalates, which enjoy numerous advantages such as wide range of raw materials, gentle reaction condition, low-cost and environmental-friendly and etc.. Furthermore, based on the antibacterial property of silver nanoparticles, the antibacterial mechanism and applications were described. The development of silver nanoparticles in antibacterial application was also prospected, such as antibacterial coating and antibacterial packaging.
Dry-wet spinning process was used to gain graphene oxide/polyimide composite fibers, then graphene/polyimide composite carbon and graphite fibers were obtained through carbonized and graphitized. Different graphene oxide contents of the composite carbon and graphite fibers were measured by thermal gravimetric analysis, Raman, mechanical properties, electrical properties, SEM and so on. The results show that when the GO content is 0.3%(mass fraction, the same below), the thermal property of the graphene oxide/polyimide composite fibers is the best. The mechanical and electrical properties are obriously improved by the addition of GO, graphitization degree also increases. When the composite carbon fibers are treated at 2800℃, GO content increases to 2.0%, the thermal conductivity of the composite graphite fibers reaches 435.57W·m-1·K-1 and cross-section structures of carbon fibers are more compact.
The surfaces of glass fabric (GF) were attached with multi-walled carbon nanotubes (MWCNTs) through electrostatic absorption and physical deposition methods, thus the MWCNTs attached GF reinforced epoxy composites based on the GF-d-CNTs and GF-a-CNTs multiscale reinforcements were prepared by vacuum-assisted resin infusion molding (VARIM) technique. Tensile properties, flexural properties, interlaminar shear strength, dynamic viscoelasticity and microstructure of composites were measured and characterized using the static and dynamic mechanics methods, scanning electron microscope, Fourier transform infrared spectroscopy, respectively. The results show that the network structures of MWCNTs attached GF, like "nanobarbed wires", are identified to improve the fiber/matrix adhesion strength and the toughness of resin through the micromechanical interlocking, which exhibits an evident enhancement in glass transition temperature (Tg). As compared to the GFRP without MWCNTs, the mechanical properties of GF-d-CNTs composites are significantly higher, the tensile strength and modulus, flexural strength and modulus and interlaminar shear strength of GF-d-CNTs composites increased by 14.5%, 37.9%, 26.2%, 36.6% and 31.5%, respectively. Moreover, the Tg of GF-a-CNTs composites is improved by 8.9℃.
The effect of different length-diameter ratios of carbon fibers (CF) on damping property of CF/EP composites was investigated. The CF was coated with copper structurally and the copper coated CF (Cu-CF) was verified by SEM. The mechanical, electrical and damping properties of composites were studied. The results show that the copper plating is coated on the surface of CF uniformly; the addition of a little large length-diameter ratio CF can enhance the impact strength of CF/EP composites effectively, while the bending strength decreases; the addition of more small length-diameter ratio CF can also improve the mechanical properties of the composites. In addition, the large length-diameter ratio CF can heighten the conductivity and damping property of composites easily.
Aimed at ex-situ toughening technology and Z-direction RTM process, Darcy's law was modified by introducing the saturation parameter. The partial differential equation describing the unsteady flow of the resin in the fiber preform was established. The effect of process parameters such as volume flow rate, resin viscosity and fiber preform's permeability during the constant flow process on the injection pressure was investigated. The resin flow between intra-tow and inter-tow of the preform with untoughened layers and toughened layers was simulated. The results show that the numerical simulation results are reliable. The inner pressure in the fiber performs increases with the increase of injection time. The injection pressure increases linearly with the increase of volume flow rate and resin viscosity, while decreases with the increase of fiber preform's permeability, which accords with Darcy's law. The infiltration visualization of resin flow through meso-scale and micro-scale fiber preform is realized, which provides an important supplement for prediction of the macro-flow in fiber preforms and provides guidance for actual process.
Super-wettability Cu mesh(200PPI) was successfully fabricated by direct oxidation, liquid deposition and vapor deposition in order to expand its application ranges and enhance microstructure effect. The structure, morphology and wettability of Cu mesh were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction, contact angle instrument and high speed video, and the optimum preparation process of film layer was obtained. The copper mesh with a layer of knife-like flower film shows super-hydrophilic wettability on which the spread velocity of water is 3.5m/s; moreover, the super-hydrophilic mesh with hybrid structures can be switched into super-hydrophobic material (>150°) by liquid deposition and vapor deposition methods; the optimum fabrication conditions to achieve super-hydrophobic performance >150° are oxidation time of 15min, oxidation temperature of 96℃, liquid deposition time of 30min and the treat temperature of 180℃ for 20min. Meantime, hybrid gaps of knife-like flowers are considered as the main reason of the super-wettability of meshes.
The raw Y2O3 powder was classified and graded based on modified co-sedimentation mathematical model, using the size distribution of W particles as the known condition. Y2O3-W continuous graded materials with the composition distribution index P values of 1.0, 0.7, 0.3 and 0.1 were prepared by co-sedimentation and hot-pressing. The results show that the Y2O3 powder consistent with the design requirements can be obtained by graduation method. The gradient continuity of materials can be verified by microstructure observation and hardness testing.
The anode oxide of nanocrystalline Mn-Mo-Ce was prepared by anode electro-deposition technology, and its nanostructure and selective electro-catalytic performance were investigated using the SEM, EDS, XRD, HRTEM, electrochemical technology and oxygen evolution efficiency testing. Furthermore, the selective electro-catalytic mechanism of oxygen evolution and chlorine depression was discussed. The results show that the mesh-like nanostructure Mn-Mo-Ce oxide anode with little cerium doped is obtained, and the oxygen evolution efficiency for the anode in the seawater is 99.51%, which means a high efficiency for the selective electro-catalytic for the oxygen evolution. Due to the structural characteristics of γ-MnO2, the OH- ion is preferentially absorbed, while Cl- absorption is depressed. OH- accomplishes the oxygen evolution process during the valence transition electrocatalysis of Mn4+/Mn3+, completing the selective electro-catalysis process. Ce doping greatly increases the reaction activity, and promotes the absorption and discharge; the rising interplanar spacing between active (100) crystalline plane promotes OH- motion and the escape of newborn O2, so that the selective electro-catalytic property with high efficient oxygen evolution and chlorine depression is achieved from the nano morphology effect.
Ni0.5Zn0.5Fe2O4 nanoparticles were synthesized by thermal decomposition method. The influence of reaction conditions such as the amount of the surfactant, refluxing temperature and time on the size, morphology and dispersibility was investigated. The structure, morphology and magnetic properties of the samples were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM) and vibrating sample magnetometry(VSM). The results indicate that increasing the amount of the surfactant is beneficial to obtain samples with smaller particle size and better dispersibility, and the improving refluxing temperature and extending refluxing time is beneficial to obtain samples with larger particle size, but with wider size distribution. The saturation magnetization of the sample is determined to be 49.38A·m2/kg, coercivity is 7143.20A/m and remanent magnetization is 5.76A·m2/kg with ferrimagnetic behavior at room temperature when the reaction condition is determined as follows, the amount of TOPO is 0.6mmol, the refluxing temperature is 260℃ and the refluxing time is 1h.
Nickel-based bond coating and composite functional coating were sprayed on leaf blade steel material FV520B successively by using air plasma spraying system. NiCrBSi-Mo powder deposition rate, coating porosity, bonding strength and surface hardness were tested. The results indicate that, for the NiCrBSi-Mo/Ni coating, bond coating with 180-220μm thickness can improve NiCrBSi-Mo powder deposition rate while the surface coating with lower porosity, higher bonding strength and high hardness is prepared; the increase of bond coating thickness can lead to increase of functional coating porosity in the bottom and speed up the process of porosity attenuating in the vertical direction.SEM analysis found that the increase of bond coating thickness results in the droplet deposition morphology change in the bending interface with the functional coating. The defects of bond coating have genetic influence on composite functional coating. Bond tensile test results show that excessive bond coating thickness will cause fracture in the interface between bond coating and functional coating during the stretching process; in different grinding surfaces, Vickers hardness of test blocks with a certain bood coating thickness attenuates slowly in the vertical direction. NiCrBSi-Mo/Ni coating not only maintains high surface hardness, but also increases the coating thickness to repair surface damage.
Carbon nanotube (CNT) reinforced aluminum matrix composites were fabricated by powder metallurgy route, including in-situ chemical vapor deposition synthesis and ball-milling process. The effect of ball-milling process on the microstructure and mechanical properties of CNT/Al composites was investigated. The results show that the best tensile properties of CNT/Al composites can be achieved without adding any process control agent; with the increment of milling time, CNTs are gradually embedded into Al matrix and the composite microstructure becomes more dense and uniform. The hardness and tensile strength of CNT/Al composites continuously increase with the increase of milling time; however, the elongation firstly increases and then decreases. The composites after 90min of milling show a good balance between strength and ductility, and the hardness and tensile strength of which is 1.4 and 1.7 times higher than that of pure Al respectively, with elongation of 17.9%.
The limit drawing ratio is influenced by the bending and unbending effect during reverse deep drawing of plate. The 5A06 aluminum alloy plate widely applied in aerospace industry was used, and the reverse deep drawing of the 4.5mm thick plate was investigated experimentally and numerically. The stress and strain distributions of plate were analyzed, the deformation behaviour was discussed for three types of cross section of die during the reverse deep drawing process; moreover, the changing rule of strain paths with the die profile was also discussed. Results show that a maximum radial stress is induced by the bending effect at the transient region between the inside die radius and straight wall, where a radial stress and strain gradient along the thickness direction appears and the fracture is easy to occur. For the semi-circle profiled die structure, the limited punch stroke is 203mm which is increased by 40% than that for the die with a planar profile section. The semi-circle profiled die structure can reduce the bending effect, effectively reduce the stress gradient and the maximum stress value in the transient region, and is helpful to improve the limit drawing ratio of the 5A06 aluminum alloy plate.
Hydroformed aluminum hollow components with various sections have been widely used in the field of automotive lightweight engineering. The main manufacturing process of the component is that the tube is pre-formed by CNC bending, and then hydro-formed into the desired shape. The springback, cross section distortion and wrinkling defects caused by bending will affect subsequent hydro-forming process. Theoretical model of tube plastic bending and model of material were established, and the theoretical springback value of any bending angle was obtained by the combination of equilibrium equation and total strain theory, the undercut defect was avoided effectively during hydroforming. The cross section un-roundness was decreased from 7.55% to 1.43% by the improvement of the core shaft, and the fracture of bend tube during hydroforming can be significantly avoided. The wrinkle defects formed in tube bending cannot be eliminated by hydroforming. The 6063 aluminum components with various sections were developed by the technology experiment, and the parts without any defects were obtained. The dimensional precision of 47 hydroformed components were measured, and the maximum dimensional deviation is 1.08mm (1.63%), and the dimensional precision meets the requirements.
Effects of Zn on microstructure and mechanical properties of Mg-Y-Nd-Zr as-cast alloys were investigated by the optical microscopy(OM), scanning electron microscopy(SEM), X-ray diffractometry(XRD) and the mechanical properties test. The results show that the grain size of Mg-Y-Nd-Zr-xZn(x=0.0%, 0.5%, 1.0%, 1.5%, mass fraction)alloys is greatly refined with the increase of Zn content, which is refined from (57±0.8)μm to (30±0.3)μm. The volume fraction of eutectic structure at grain boundary increases gradually. Mg12Nd phase and Mg24Y5 phase exist mainly in Mg-Y-Nd-Zr as-cast alloy. With the addition of 0.5%Zn, Mg12YZn phase appears at the grain boundary. With the increase of Zn, the volume fraction of Mg12YZn phase and the mechanical properties of the alloys increases gradually. The alloy containing 1.0%Zn exhibits the optimal mechanical properties, the ultimate tensile strength, yield strength and elongation are (208±5.9), (159±3.9) MPa and (7.5±0.2)%, respectively; comparing with the alloy without the addition of Zn, the ultimate tensile strength, yield strength and elongation increase by 18, 42MPa and 1.2%.
Based on first-principles density functional theory, the Fe/Al interface model of steel/aluminum laser welding was constructed by layer technique. The Fe/Al interface was studied by metal atom X (X=Sn, Sr, Zr, Ce, La).The results show that Sn, Sr and Ce preferentially displace the Al atoms at the Fe/Al interface, while La and Zr preferentially displace the Fe atoms at the Fe/Al interface. Alloying promotes the transfer of Fe/Al interfacial electrons between different orbits, enhances the ionic bond properties of Fe-Al, improves the Fe/Al interface binding capacity, improves the brittle fracture of Fe/Al interface, and the alloying effect of Sn most notable. On the basis of this, the laser lap welding test of Sn and Zr powder was carried out on 1.4mm thick DC51D+ZF galvanized steel and 1.2mm thick 6016 aluminum alloy specimen. The results show that the addition of powder can promote the flowability of the molten bath and change the composition and microstructure of the joint interface. The tensile strength of the steel/aluminum joint is 327.41MPa and the elongation is 22.93% with the addition of Sn powder, which is obviously improved compared with the addition of Zr powder and without the addition of powder.
The intergranular corrosion and exfoliation corrosion properties of 7475-T7351 aluminum alloy plate for aviation were investigated, and the corrosion behaviors of the alloy were analyzed by metallographic analysis(MA) and transmission electron microscope(TEM). The results show that no obvious intergranular corrosion is observed, but exfoliation corrosion grade of 7475-T7351 aluminum alloy increases from EA on surface to EC in the core. The exfoliation corrosion of 7475 alloy plate is mainly because of the typical lamellar structure, and the pathway formed by galvanic corrosion on grain boundary. The expansion of grain boundary corrosion product volume produces the wedging force, makes intergranular corrosion grow along the direction in parallel with the surface, and then gradually evolves into exfoliation corrosion. The degree of recrystallization decreases gradually from the surface to center, and the grain length-to-width radio increases, which inclines to exfoliation corrosion and leads to the exfoliation corrosion grade increasing from surface to center.
The multiaxial fatigue behavior of 2A12 aluminum alloy was studied with SDN100/1000 electro-hydraulic servo tension-torsion fatigue tester under different stress amplitude ratios, the fracture morphology and the fatigue loading curve were observed to study the failure mechanism. The results show that, under the one stage loading condition, the fatigue life prolongs with the stress amplitude ratio increasing. Under pure torsion loading, smooth and even area exists in the fracture surface. As the stress amplitude ratio increases, the number of scratch reduces, the fatigue striation and some special morphology such as the fishbone pattern, scale pattern and honeycomb pattern can be observed; under cumulative paths of different stress amplitude ratios, the variation of multiaxial fatigue life changes with first stage loading cycles; under cumulative paths of high-low stress amplitude ratio, the cycle hardening occurs obviously in the axial direction for the first stage high stress amplitude ratio loading and 2A12 alloy shows training effect.
To adjust the oscillation of renewable energy sources in the discontinuous generation of electricity, power plants will be used to stabilize the fluctuations. Fatigue creep damage on power plant components will be increased, during the frequent start-up and shut-down processes of the units. A pre-loading experiment plan was introduced through the analysis on the insufficient stress-strain behavior of gas turbine rotor under thermomechanical loading described by an existed lifetime estimation model. Based on the data of the pre-loading experiments, the current life prediction model was optimized. By comparison of the simulated stress-strain behavior and estimated fatigue creep life near working condition test at alternating temperatures, the optimized life prediction model was evaluated.
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Founded in 1956 (monthly) ISSN 1001-4381 CN 11-1800/TB Sponsored by AECC Beijing Institute of Aeronautical Materials |
