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31.
On the High-Temperature Oxidation of Cu-Rich Cu-Ni Alloys 总被引:9,自引:0,他引:9
Cu-2 wt.%Ni and Cu-5wt.%Ni were oxidized at 800to 1050°C and oxygen pressures from from 5 ×10-4 to 1 atm. The oxidation, as measured bythermogravimetry, was approximately parabolic. The oxidescales could be divided in two main regions: An outerregion consisting of copper oxides and an inner porousregion, which consists of Cu2O with dispersedNiO particles. NiO particles exists as internal-oxide particles. The interface between the two layersreflects the original surface, which shows that theouter part grows by outward Cu diffusion via vacancies.The inner part grows by outward diffusion of copper and inward transport of gaseous oxygen by thedissociative-transport mechanism. The amount ofporosity, the relative thickness of the inner layercompared to the total thickness of the scale, and theoxidation rate as a function of Ni content was dependenton the reaction conditions. 相似文献
32.
《Journal of Adhesion Science and Technology》2013,27(15):1483-1496
Adhesion of fluorine rubber to metals is an important issue. The aim of this work was to develop a new kind of adhesive for bonding fluorine rubber to metals. A new modified epoxy adhesive containing a special tackifier resin obtained from polysulfones with a high heat deflection temperature (HDT) was prepared. Study on the curing behavior of the adhesive was carried out. Properties of the adhesive and the effects of several main factors were studied by gelation time test, differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectroscopy. The optimum amount of the tackifier resin was found to be 50 phr; the average tensile lap shear strength could be achieved to a level of 8–10 MPa. Infrared attenuated total reflection (IRATR) spectroscopy indicated that the tackifier resin accelerated the establishment of epoxy resin adhesion to steel, and also promoted bonding and vulcanization of fluorine rubber. Easy diffusion of cyanamide (decomposition compound of dicyandiamide (DICY) in the curing process) into epoxy resin and fluorine rubber facilitated the dissolution and reaction of DICY, and also promoted formation of complex bond between fluorine rubber and adhesive, hence an enhanced adhesion of fluorine rubber to metal was achieved. 相似文献
33.
《Science & Technology of Welding & Joining》2013,18(8):738-759
AbstractFriction welding is now well established as a means of joining many different types of materials, because it has proved itself to be a reliable and economical way of producing high quality welds. The present paper introduces different friction welding processes, their advantages and shortcomings. The history of friction welding and typical applications are also reviewed. In the context of friction welding, a number of subjects, such as frictional behaviour, joining mechanism, interface temperature and heat generation, still exist, where different concepts for explanation of the physical mechanisms have been proposed by different investigators. To clarify some inconsistencies in the interpretation of the friction welding process, a thorough review and critical assessment of the literature associated with this process is attempted. 相似文献
34.
CHEN Weishan CHEN Hua LIU Junkao School of Mechatronics Engineering Harbin Institute of Technology Harbin China 《机械工程学报(英文版)》2007,20(2):69-72
A new method solution for the direct displacement of parallel mechanism,wavelet network method,is proposed. Comparing with the classical analytical and numerical methods,this method can be extended to any parallel mechanism with any selected degree of freedom and configuration. A wavelet network suiting to approach multi-input and multi-output system is constructed. The network is optimized by analyzing the sparseness of input data and selecting the fitting wavelets by orthogo-nalization method according to the output data. Then it is applied to solve the direct displacement of a general six-degree-of-freedom parallel mechanism as a numerical example. For comparison purposes,a BP neural network is also used for this problem. Simulation results show that the wavelet network performs better than BP neural network. In addition,the wavelet network learns much faster than BP network. 相似文献
35.
36.
《腐蚀工程科学与技术》2013,48(6):442-448
AbstractIn a self-designed occluded corrosion cavity (OCC) simulated cell, the inhibition mechanism of sodium laurate (C12H23O2Na) to the underdeposit corrosion of the N80 steel in a neutral 0·2 mol L–1 NaCl solution was studied by electrochemical methods, including measurements of polarisation curves, coupling currents, polarisation resistances, electrochemical impedance spectra (EIS) and ion selectivity of the scale film. The results show that C12H23O2– could form a monomolecular adsorption film on the N80 steel surface in the studied solution, whose adsorption behaviour would follow Flory–Huggins isotherm model, and inhibit both anodic and cathodic processes. C12H23O2– displays good inhibition performance to the underdeposit corrosion of the N80 steel in the studied system, which could be mainly attributed to the inhibition to the electrode processes of the bulk cathode and occluded anode, the increase in the resistance of the corrosion deposit layer and the prevention to the autocatalysing acidification effect in OCC. The last two factors might be related to the conversion of the deposit layer from anion selectivity to cation selectivity and the formation of a hydrophobic layer on the wall of the micropores in the deposit layer by adsorption of C12H23O2–. 相似文献
37.
《Materials Science & Technology》2013,29(1):82-86
AbstractThe mechanical behaviour and microstructural evolution in tension of NiAl - 9Mo eutectic alloy at 1100 ° C and strain rates from 10-5 to 10-3 s-1 have been investigated. High values of strain rate sensitivity index, but relatively small elongations between 150 and 200%, have been observed. Tensile specimens with various strains were quenched in water to preserve the dislocation structures for TEM examination. The TEM results show that the dislocation configuration and density change significantly with an increase in strain rate, and therefore correspond to different deformation mechanisms. At a low strain rate (5.5 × 10-5 s-1), the dislocation density is relatively low and dislocation activity is regarded as an accommodation mechanism for grain boundary sliding. In contrast, the high density of dislocations as well as clear subboundaries observed in grains at a high strain rate (5.5 × 10-4 s-1) suggest that the dislocations are active directly in response to the applied stress as well as participating in the relaxation process of grain boundary sliding by subboundary formation. Thus, grain boundary sliding is mainly responsible for superplastic deformation at a low strain rate, while superlastic deformation at a high strain rate is controlled by the combined operation of both grain boundary sliding and dynamic recovery. 相似文献
38.
《应用陶瓷进展》2013,112(6):350-353
AbstractZnSe thin films were prepared on transparent indium tin oxide (ITO) glasses by electrodeposition at 70°C. Linear sweep voltammograms were performed to get details about electrochemical reactions on indium tin oxide substrate. Deposition mechanism was discussed in conditions of static electrolytes and stirring ones. The results indicated that the catalysis of H2Se on surface of ITO glass has accelerated Se(0) accumulation which restrained Zn2+ ions diffusion into lattice position. Cubic ZnSe films could only be obtained at ?900 mV from stirring solution. Mechanical agitation excitated the reaction of Zn2+ ions with reduced Se species, which decreased Se(0) accumulation onto the solid electrode. 相似文献
39.
Mongeon P.-É. 《粉末冶金学》2013,56(3):263-269
AbstractPlastic flow surfaces for metal and metal/composite powder compacts with variable cohesive strength are derived using the Beltrami total strain energy criterion, modified to permit asymmetric yielding. The present theory thus includes the domains of both soil mechanics and powder metallurgy, covering both granular and porous microstructures of varying bond strengths over all possible densities. A quantitative theory of the expansion of non-bonded particle compacts under certain combinations of applied shear stress and pressure is given. Physical models of the failure mechanisms are provided, their applicability depending on the particle interface strength. If the particle interface lacks strength, the flow surface is identical to that of the ‘critical state’ criterion of soil mechanics. The flow ellipse lies entirely within the negative pressure domain and failure occurs at the particle interface by various mechanisms including frictional slip. At the other extreme, if the particle interfaces are as strong in shear as the particles, failure occurs by plastic shear of the particles and the flow ellipse is centred at the origin. Density–stress and density–aspect ratio maps are shown which define these domains. Theoretical predictions compare well with the results of data compiled from the literature as well as data from tests performed in this study on cold pressed Al and Al/SiC powder compacts. 相似文献
40.
《钢铁冶炼》2013,40(3):219-223
AbstractLiquid ejections from gas stirred melts can be classified into small film and jet droplets caused by bubble bursting and larger splashes resulting from gas channels formed at higher exiting gas velocities. In view of the conditions in ladle metallurgy, experimental investigations were carried out at moderate to low gas flowrates in an arc heated, bottom stirred 150 kg steel melting furnace and an 80 L water tank. Droplets were collected at different heights above the melt level, while gas flowrates, viscosities, surface tensions, and slag layer thickness were varied. The number of steel droplets collected decreased greatly with height (in the range 30-110 mm) and with size (in the range 0·1-1·8 mm). Calculations showed that the entrainment of droplets is strongly influenced by the velocity of upward flowing gases. While at low flowrates typical for secondary metallurgy (0·1 m s -1), only droplets <50 μm will be entrained, BOF (basic oxygen furnace) typical flowrates (20-50 m s -1) will cause particles up to 500 μm to be carried into the dust removal systems. Higher surface tensions resulted in increased droplet ejection, while higher viscosities led to a decreasing quantity of ejected melt. Slag layers led to a decrease in the ejection of steel droplets and to an increase in ejected slag but they did not completely stop steel ejection, because gas bubbles appear to entrain steel drops when they rise through the slag layer. Bubble bursting in a pure slag system caused large but few slag droplets due to the high viscosity of the slag as compared to the steel melt. 相似文献