最新刊期
卷 ， 期 11 ， 2006
- 摘要：Al2O3/ZrO2（4Y） self-growing composite ceramics, which is composed of major rod-shaped sapphires with 8.012.0 aspect ratio and minor lamellar α-Al2O3 phase, and within the sapphires t-ZrO2 nano-micron fibers are embedded, has been prepared with eutectic growth of melts in the condition of severe undercooling degree by introducing proper ZrO2 （4Y） powder into the thermit on the basis of oxidation-reduction reaction of the thermit and liquid-liquid phase separation of ceramics/metal under the gravity, the relationship of microstructure with mechanical behavior has been understood by measuring mechanical properties of the composites and observing crack propagation paths. The results show that the flexural strength and fracture toughness of ceramic composites are 1 256 MPa and 13.2 MPa·m 1/2 , respectively. A number of low energy interface in a nano-micron scale distance between Al2O3/ZrO2（4Y） and compressive residual stress in the sapphires results in the reinforcement of the rod-shaped sapphires and ceramics matrix, which exerts the crack to propagate along the rod-shaped sapphires. Meanwhile, crack-bridging and pull-out of sapphires, crack-bridging and frictionally interlocked effects of plate-like α- Al2O3 grain in the wake of crack tip also render the crack stabilization to arise.关键词：Al2O3/ZrO2（Y2O3）Composites Ceramics;Rod-shaped Sapphires;Nano-micron Fibers;Eutectic Growth;In-Situ Toughening
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发布时间：2023-12-18 - 摘要：Effects of high pressure solidification on dendritic morphology of Al-9.6Mg alloy have been described by Olympus optical microscope. The results demonstrate that while the microstructural dendritic is coarse and broken under normal pressure, dendritic arm keeps completeness in which secondary dendritic arm spacing is decreased and major primary dendritic arm is grown under high pressure. Evolution mechanism of dendritic morphology has been expounded from the viewpoint of effects of high pressure on constitutional undercooling and heat undercooling as well as solute diffusion. High pressure solidification, as an extreme solidification condition, can provide a new approach to change the structural morphology in the alloy.关键词：High Pressure Solidification;Al-9.6Mg Alloy;Dendritic Morphology
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发布时间：2023-12-18 - 摘要：AZ91 Mg metal matrix composites have been prepared by the squeezing-infiltration method, in which preform was fabricated with crystallized alumina silicate short fibers as reinforcement and aluminum phosphate as binder,and by combining dry method with green method. The casting defects and microstructure in Mg metal matrix composites have been described by means of OM （optical microscope） and SEM（scanning electron microscope）. The experimental results indicate that neural aluminum phosphate solution is one of the best binders for fabricating alumina silicate fibers （Al2O3-SiO2/AZ91） reinforced Mg metal matrix composites. The structural shrinkage porosity in the MMCs can be effectively reduced, or even be eliminated by complex squeezing-infiltration process.关键词：Aluminum Silicate Short Fibers;Aluminum Phosphate Binder;Squeezing-infiltration;Magnesium Metal Matrix Composites
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发布时间：2023-12-18 - 摘要：The soften behaviors of Cu-0.2Cr-0.1Ag alloy with high performance have been investigated by analyzing microstructure and testing mechanical properties with annealing at the temperature from 573 to 1 073 K in electric resistant furnace. The results reveal that soften temperature about 723 K of the Cu- 0.2 Cr-0.1Ag alloy can be observed, and the growth of grain in the alloy will be restrained by solid solution Ag particle and dispersive Cu particle. The soften rate and strength of Cu-0.2Cr-0.1Ag alloy at 573 K,are 98.3% and 531MPa, respectively, which are obviously higher than those of pure Cu and Cu-Ag alloy, exhibiting better heat resistance.关键词：Cu-0.2Cr-0.1Ag Alloy;Soften Behavior;Annealing Temperature
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发布时间：2023-12-18 - 摘要：The influence of low-voltage electric current pulse （LVECP） on solidified structure of Al-4.5Cu alloy was studied, and the effects of cooling rate, pulse voltage and treating time on grain size of the alloy were investigated. Experimental results indicate that the solidified structure of Al-4.5Cu alloy can be remarkably refined, where primary α-Mg phase is converted from developed dendrites into uniformly fine rosette grain after LVECP treatment. With cooling rate and pulse voltage increase, the grain size of Al-4.5Cu can be reduced gradually. However, with the pulse voltage increasing to 400V, grain size in the Al-4.5Cu alloy can be increased slightly. As treating time increasing from 0 to 10 min, the grain size can be decreased greatly, while the treating time is more than 10 min, grain size in Al-4.5 Cu alloy can be somewhat increased with increasing in treating time.关键词：Al-4.5Cu Alloy;LVECP;Solidification Structure
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发布时间：2023-12-18 - 摘要：Effects of quenching agent on grain boundary precipitates and precipitate free zone （PFZ） in 7055 aluminum alloy have been investigated by transmission electron microscope （TEM）. Precipitation of equilibrium η phase was observed on grain boundary in air. In the room temperature and boiling water quenched alloys, grain boundary precipitates with chain continuous distribution are somewhat different in phase sizes, and average width of PFZ are about 33 nm and 43 nm, respectively, while grain boundary precipitates in air quenched alloy are obviously different in phase size, exhibiting discontinuous distribution, and the width of PFZ is about 102 nm. The formation mechanism was approached also.关键词：7055 Aluminum Alloy;Quenching Agent;Grain Boundary Precipitates;PFZ
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发布时间：2023-12-18 - 摘要：The microstructures of A356 cast aluminum alloy prepared by phase-transformation-cooling method and by water-cooling in Cu mold have been observed by SEM（scanning electron microscopy）, DSC, XRD and TEM. Compared with that made by water-cooling in Cu mould, the primary α-phase and eutectic structure in A356 cast aluminum alloy made by phase-transformation-cooling method is greatly refined. The calculation from XRD measuring value shows that the solid solution degree of Si in primary α-phase is 2.7 %（in atom） in samples prepared by phase-transformation-cooling method while is 2.4 % （in atom ） in ones made by water-cooling in Cu mould, which demonstrates that Sn-quenching exhibits better cooling ability than water-cooling in Cu mould.关键词：Phase-transformation-cooling;Water-cooling in Cu Mould;Aluminum Alloy;Microstructure
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发布时间：2023-12-18 - 摘要：A novel method based on modified particle swarm optimization （IPSO） with mutation algorithm was proposed to optimize water quantity in secondary cooling process in the continuous slab casting. An mathematical model of heat transfer in solidification process of the continuous slab has been developed based on solidification principle with a time-space finite volume method, and the simulated results based on the model are well in agreement with the experimental ones. Then, water-quantity in secondary cooling process was optimized by IPSO. Surface temperature-reduction rate and surface temperature-increment rate on the continuous slab casting at every stage tends to flat using optimized secondary cooling system, which is accordant with the requirements of metallurgical principle improving cooling process of the slab and product quality.关键词：Modified Particle Swarm Optimization;Continuous Slab Casting;Secondary Cooling;Optimization Control
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发布时间：2023-12-18 - 摘要：The possible defect locations encountered in the castings were predicted by simulating filling and solidification process of gear box of the car using a CAE system. Based on simulated results, the gating system for the filling has been optimized. The results show that when liquid alloy was poured smoothly, the casting defects in the casting during pouring process have been decreased obviously by means of modified gating system, which improves the whole quality of aluminum alloy die castings关键词：CAE;Die Casting;Gating System
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发布时间：2023-12-18 - 摘要：Mechanical properties and microstructure of semi-solid MB15-RE magnesium alloy billets prepared by ECAE have been investigated. The results show that the mechanical properties of the MB15-RE magnesium alloy prepared by ECAE can be improved remarkably. Tensile strength and elongation of the alloy are increased by 312.5 MPa from 154.7 MPa and by 13% from 7.3% in as-cast, respectively. The semi-solid microstructure with fine, uniform and spherical grain can be obtained in ECAE, in which the grain with 520 μm in size and 1.3 in roundness can be formed.关键词：MB15-RE Magnesium Alloy;ECAE;Mechanical Properties;Microstructural Evolution
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发布时间：2023-12-18 - 摘要：Filling process of A356 alloy in semi-solid thixo-forming die casting and in conventional die casting has been simulated based on a Flow-3D system. Simulated results indicate that filling process in semi-solid thixo-forming die casting is smooth, while it is turbulent so gas-hole, gas-entrapped etc., were easily generated in conventional die casting through with the two kinds of die casting in the same mould structures. However, there exists the same flow channel in both semi-solid thixo-forming die casting and conventional die casting.关键词：Semi-solid;Thixo-forming;Numerical Simulation
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发布时间：2023-12-18 - 摘要：Solidification characteristics and microstructure of squeezing castings with large ratio of height to diameter have been investigated by numerical simulation and experiments. The results show that pressure distribution in the squeezed castings with large ratio of height to diameter is very uneven, in which the higher pressure is exhibited at the position near to the punch so that faster solidification rate can be obtained. Pressure-increment can result in the refinement and the occurrence of plastic deformation of the grain. There exists interface at down-position microstructure of thin-walled parts with large ratio of height to diameter, where microstructure is obviously different in two sides.关键词：Squeezing Casting;Castings with Large Ratio of Height to Diameter;Solidification;Microstructure
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发布时间：2023-12-18 - 摘要：The effects of various factors and interaction among factors on the quality of the squeezed castings have been approached. It gives three phases, namely, the full appraisal in the forepart, strictly control in the medium and strictly management in the last. It is a necessary condition to get qualified squeezed castings by reasonably controlling and adjusting parameters according to the change of the conditions and the interaction among the technical parameters. It is a basic guarantee for the high-efficiency by synthetically controling the quality of squeezed castings.关键词：Squeezing Casting;Quality;Mould;Synthetically Control
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发布时间：2023-12-18 - 摘要：The structural design, parting surface selection, container and moving mould design as well as push mechanism of die casting die have been expounded based on analysis of processing performance of oil filter bracket. To the convenience of manufacturing and application, an upside-down design for the container and moving mould structure was conducted, namely, core with large close force and complex shape was designed as container and cavity for forming surface was designed as moving mould. In addition, three processing concaves were designed and push-mechanism was set at side-core-drawing, which can reduce mould volume and decrease manufacturing cost of the die.关键词：Die Casting Die;Die Structure;Parting Surface;Push Mechanism
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发布时间：2023-12-18 - 摘要：Aluminum motorcycle left-cover has the features of uniform wall-thickness and large profile dimension. Parting surface was designed in terms of the shape, dimension of the parts and requirements of gating system and die-released. Center-spreading gating system was adopted, and ingate was designed at thick location of the parts, which is helpful to transferring pressure and to filling and feeding of liquid aluminum alloy. Meanwhile, an over-flow exhausting system is set at the position where is a blind corner or is directly impacted by liquid aluminum alloy to ensure smoothly filling, which is beneficial to exhausting gas and waste-liquid alloy. Push-bar was homogeneously set at the thick position of parts to ensure uniform push-pressure to avoid the deformation of the parts.关键词：Parting Surface;Gating System;Over-flow Channel;Parts Quality
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发布时间：2023-12-18 - 摘要：Elimination of shrinkage hole encountered down ingate/riser investment castings and is an effective way to increase production yield by rationally designing ingate/riser in shell-mold in the investment casting and using lunkerite proportion. Through rationally designing ingate /riser system and effectively using the lunkerite proportion, shrinkage hole and low production yield were eliminated effectively.关键词：Investment Casting;Lunkerite;Production Yield;Ingate/riser System
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发布时间：2023-12-18 - 摘要：A novel three dimension rapid manufacturing for pattern has been proposed, in which the computer was used to control pin pattern hot knife to evaporate the unnecessary materials by a laminated method. The rapid manufacturing method is suitable for producing single or a few batches of expandable pattern, characterized by high efficiency, low cost and high dimensional precision through verification from some typical sample production.关键词：Lost Foam Casting;Expandable Polystyrene;Pattern;Rapid Manufacturing
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发布时间：2023-12-18 - 摘要：Disperoids Cu matrix composites have been prepared by blowing ceramic particle into liquid Cu with high-speed gas-flow to investigate the effects of particle surface treatment on wettability of Cu-ceramic particle interface and bonding strength between Cu and ceramic particle. The results reveal that surface treatment of ceramic particle can obviously improve interfacial bonding strength of the composites. Furthermore, hardness, yield strength and electric conductivity of the composites can be improved to a certain by adding compound dispersively ceramic particle （treated MgO particle and treated CeO2 particle）.关键词：Disperiods;Surface Treatment;MgO;CeO2;Cu Matrix Composites
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发布时间：2023-12-18 - 摘要：Ni-CeO2 nano-composites were prepared by an electro-forming method. Effects of CeO2 particle concentration in electrolyte, cathode current density and electrolyte temperature on CeO2 content in the composites and the micro-hardness of the composites have been investigated, and the surface morphology of the nano-composites has been observed. It is found that the optimized processing parameters for preparing Ni-CeO2 nano-composites can be obtained including CeO2 particle concentration of 40 g/L, cathode current density of 4 A/dm2 and electrolyte temperature of 55 ℃ as well as pH value of 3.8. The nano-composites containing 8.5% CeO2 content were prepared with the optimized processing parameters, which have smooth surface morphology and compact microstructure, and exhibit higher micro-hardness than those of the pure Ti, reaching 598 HV.关键词：Electro-forming;Nano-composites;CeO2;Nano-particle
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发布时间：2023-12-18 - 摘要：Effects of different processing techniques on corrosion resistance of Pb-free brass have been investigated by dezincification corrosion depth testing, potential tests, optical microscope and SEM. The results show that dezincification corrosion resistance of cold-drawing Bi-brass is worse than that of hot-rolled Bi-brass and as-cast Bi-brass as a results of β phase distributed along cold-working direction and the increase of dislocation density and residual stress. The corrosion resistante of hot-rolled Bi-brass is equivalent to that of as-cast Bi-brass, which is attributed to the dynamic recovery and recrystallization during hot-rolling process. The passivation phenomenon of the brass in 3% NaCl solution can be observed due to the creation of passive film of Cu2O or CuCl2. Occurrence of pitting corrosion in cold-drawn brass can be found after the polarization measurement.关键词：Pb-free Brass;Bi;Cold-drawing;Hot-rolling;Dezincification;Electrochemical Corrosion Property
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发布时间：2023-12-18 - 摘要：Effects of Fe,Ni and Cu on corrosion resistance of AXJ530 magnesium alloy have been investigated by a 5% NaCl slat spray testing and a 5% NaCl salt water immersion testing as well as in an electrochemical method. The effects of Fe and Cu contents less than 6.9×10 -5 on the corrosion resistance of magnesium alloy can be almost ignored while the corrosion resistance of the magnesium alloy is greatly deteriorated wit Ni content more than 3×10 -6 in both 5% NaCl salt water immersion and the 5% NaCl salt spray environment. Fe or Cu addition can create some alveolate pit in specimen surface of the AXJ530 magnesium alloy and Ni addition can create corrosive pitting. Effects of Fe and Ni on corrosive current density in polarization curves are very similar to those of both in the 5% salt water immersion testing and in the 5% NaCl salt spray testing, however, the effect of Cu on corrosive current density is almost ignored.关键词：Magnesium Alloy;Fe;Ni;Cu;Corrosion;Polarization Curves
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发布时间：2023-12-18 - 摘要：Al-5Mg-0.3Sc alloy plate with high comprehensive properties has been developed.Effects of Sc on microstructure and properties of Al-Mg alloy were observed by OM and SEM.The results show that 0.3% Sc addition can significantly refine as-cast structure in Al-Mg alloy so that major dendritic structure can disappears in the microstructure.Al-5Mg-0.3Sc alloy is equivalent to 2Al2（LY12）alloy in mechanical proerties but is higher than ones in corrosion resistance in sea-water.So the Al-5Mg-0.3Sc alloy can take place 2A12 alloy plate to be used as repairing material for failure aluminum structure plate in the plane.关键词：Sc;Al-Mg Alloy;Micristructure;Properties;Plane Structure
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发布时间：2023-12-18 - 摘要：Friction stirring welding （FSW） of AZ31 magnesium alloy in ECAP with a thickness of 15 mm has been investigated, and the formation characteristics and mechanical properties of welding joint have been analyzed. The results indicate that average tensile strength of the welding joint is 91% of that of base materials with welding speed of 37.5 mm/min and rotating speed of 750 r/min of welding pin. The hardness of joint is greatly different in advancing side and in retreating side, however, which is lower than that of the base materials, and the maximum values can be observed at about thermal effect zone. Tensile fracture morphology is characterized by ductile rupture.关键词：ECAP;FSW;Magnesium Alloy;Mechanical Properties
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发布时间：2023-12-18 - 摘要：Effects of Sr on the solidification of AZ91D magnesium alloy have been observed by XRD （X-ray diffraction） and DSC. The results show that although Si addition has slightly affected on solidus temperature of the AZ91D Mg alloy, it can greatly decrease the liquidus of the alloy to reduce crystallized temperature interval. With 0.2% or 0.5% Sr addition, major Sr is dissolved into the alloy rather than forms new phase in ones. However, with 0.8% Sr addition, high melt point Al4Sr phase is created in the AZ91D alloy.关键词：Magnesium Alloy;Sr;Solidification Process
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发布时间：2023-12-18 - 摘要：Microstructures of as-cast and homogeneously annealed Al-0.8Mn-0.5Fe alloy sheet have been observed, and effects of homogeneously annealing temperature on microstructure of the alloy sheet have been approached. The uniform microstructure in alloy can be observed due to amounts of dispersively distributed fine secondary phase precipitated from the alloy after annealing at 540 ℃ for four hours. The change of grain size in the casting-rolling sheet is absent with homogeneously annealing temperature lower than 540 ℃ while the grain remarkably grows with homogeneous annealing at 580 ℃, which is ten times more than that of ones before homogeneous annealing treatment.关键词：Al-Mn-Fe Alloy;Homogeneous Annealing;Microstructure;Segregation;Precipitation
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发布时间：2023-12-18 - 摘要：Smelting of Al-Li alloy containing high Li content with vacuum micro-gravity apparatus based on electromagnetic analogue has been conducted. The results verify that segregation in the Al-Li alloy containing 5%10% Li can not be observed, and the density of the Al-Li alloy is located in the density range of super-lighter alloy. The properties of the Al-Li alloy containing 5%10% Li can approach towards practical application by improving crucible structure, heating ways and heat treatment method.关键词：Microgravity Electromagnetic Simulation;Al-Li Alloy;Mechanical Properties
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发布时间：2023-12-18
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