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  • 1
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Extrusion directly following vacuum infiltration is a special forming technique thatcombines the advantages of liquid metal infiltration and semisolid extrusion. The major advantages ofthis process are elimination of porosity and shrinkage, good surface finish, good dimensionalaccuracy, high strength to weight ratio and near net shaping. Magnesium matrix composites arefabricated usually through stirring casting, powder forming, injecting deposition, liquid metalinfiltration or die casting at present time. However few investigations on magnesium matrixcomposite are conducted for the specific characteristics of magnesium alloy, such as high chemicalactivity and easy oxidation. The present paper is focused on Csf/Mg composites obtained viainfiltration of porous short carbon fiber preform by liquid Magnesium. The complete experimentsetup is designed and fabricated by ourselves, which include the forming molds, the unit for meltingthe magnesium, the unit for vacuuming and the monitoring and collecting system of forming processparameters. In this method the whole experiment setup is vacuumed firstly. Then the pressurizednitrogen is used to infiltrate the magnesium melt through a porous preform of short carbon fibers.After the infiltration completed, the punch of the press extrude the magnesium-infiltrated preform outof the forming die to form the tubes or bars. X-ray diffraction (XRD), optical and SEM microscopeswere used to characterize the infiltration and the microstructure of fabricated composites. Thecompression test was used to characterize the mechanical properties of fabricated composites. Theresults show that the preform was infiltrated thoroughly by melt magnesium and the fabricated Csf/Mgcomposites have excellent mechanical properties compared with the magnesium alloys. Csf/Mgcomposites should be very promising candidates for automobile parts and portable electronicappliance parts in the future
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 324-325 (Nov. 2006), p. 599-602 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Porous structure is an important component in C/C composites, which directly affectsthe fatigue behavior of materials. Therefore, it is necessary to discuss the evolution of porousstructure in C/C composites under the fatigue loading. In present work, the character of porousstructure in original C/C composites was summarized and the evolution of porous structure afterfatigue loading was analyzed. The positive effect of the porous structure evolution after fatigueloading on the reinforcing behavior of fatigue was proposed as well, which could provide a basisfor further studies on the fatigue mechanisms of C/C composites
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 47-50 (June 2008), p. 455-458 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of low-level oxidation (weight loss less than 6wt.%) on mechanical property oftwo-dimension (2D) carbon/carbon (C/C) composites was investigated in present work. C/C sampleswere oxidized in a mixture gas, composed of 10vol%O2 and 90vol%N2, at temperatures of 850°C and1300°C, respectively. The strength of C/C composites before and after oxidation was measured bythree point flexural tests. At different temperature, similar influences of low-level oxidation onmechanical property of C/C samples were observed. As a result, failure of the as-received compositeswas accompanied by brittle, catastrophic reduction in force. As oxidation progressed, the fracturemodel of oxidized samples changed from brittle model to pseudoplastic failure model. Especially, thechanges of flexural strength with the weight loss increasing could be divided into two stages: (i) atlow weight loss, the strength increased with weight loss and is slightly higher than that of theunoxidized composites; (ii) at high weight loss, the strength decreased gradually with the weight loss
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 1270-1273 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The morphologies and textures of the pyrolytic carbon matrix in 2D-C/C composites aftergraphitization were investigated by means of polarized light microscope (PLM) and high resolutiontransmission electron microscope (HRTEM). The microstructure parameters of the pyrolytic carbonmatrix before and after graphitization were characterized with X-ray diffraction (XRD) technology. It wasfound that the interplanar distance of (002) planes (d002) of pyrolytic carbon matrix decreases, and themicrocrystalline stack height (LC) increases after graphitization. Graphitization treatment resulted in acoarsening of the surface texture and in the formation of circumferential cracks within the matrix. Thelattice fringes of the pyrolytic carbon matrix are continuous and longer in each domain and the (002) peakspot is smaller and more intense after graphitization
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 324-325 (Nov. 2006), p. 519-522 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Tensile properties and fracture morphologies of C/C composites used as aircraft brakedisc at different heat treatment temperature have been studied. Fracture morphologiescharacteristics of tensile sample were observed with scanning electron microscope (SEM), andfracture mechanism was analyzed. The test results show that, with increase of heat treatmenttemperature, tensile strength of C/C composites has a descend trend, whereas, breaking strain has anupward trend, and failure mode changes from brittle fracture into “pseudo-plasticity” fracture.Destructional form includes interface debonding, extraction, break and matrix damage and so on,among which interfacial failure is principal fracture mechanism
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 546-549 (May 2007), p. 1521-1524 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The influence of needling parameters on mechanical properties of carbon-carbon(C-C)composites reinforced by needled carbon cloth was studied in the present investigation. Theresults showed that needling density (ND)and needle-punching depth (PD) both had a larger effect oninterlaminar shear strength (ILSS) than on compression strength and flexible strength of NeedlingC-C(NC-C). The mechanical properties of NC-C increased with increasing punching density in therange of 20-45 punch/cm2 and also with increasing punching depth range from10 to16mm. The NC-Cwith the highest ND value of 55punch/cm2 had highest ILSS value of 27 MPa.The optimized ND andPD parameters was 30 punch/cm2 and 12mm respectively, which resulted in a high value of tensilestrength(119MPa), bending strength (220MPa) and compression strength (235 MPa) in the X-Ydirection
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 551-552 (July 2007), p. 293-296 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The aim of the study on the deformation defect is to prevent defects and to improve thequality and to control the deformation. It is important that the preventive measure could be establishedto advance the scientificity of the product and processing design. In this paper, the reasons of the outerdefects such as cracks are analyzed based on the superplasticity of the copper alloy and the process ofsolid cages in the superplastic extrusion. The prediction and numerical simulation of these typicaldefects are also carried out using the Deform-3D software grounded on the model of the rigid-viscoplastic FEM. The position, time of crack appearance and relation between the strain rate and thedefects are also studied. The simulated results are in equivalent agreement with the experiment
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 551-552 (July 2007), p. 79-83 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The superplasticity of cast copper alloys used for solid cages is studied by tests of tensionand compression in this paper. The results show that cast copper alloys exhibited superplasticitywithout any pretreatment. Cast aluminum bronze is of superplasticity at the temperatures between750~800°C with the initial strain rate 1×10-2s-1, the elongation being over 260%. Under the conditionof superplasticity compression with the strain rate (1.136~9.091)x10-4s-1 at temperatures between600~650°C, the cast lead brass presents the superplasticity effect with the maximum flow stress under2MPa
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 475-479 (Jan. 2005), p. 2713-2716 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: By using the finite element method and large strain two-dimension plane strain model,the flaking damage of Cu-Fe-P lead frame sheet is investigated. The characterization of microstructure under surface flaking is the larger Fe particles embedded in the copper matrix. The numerical analysis reveals that at the interface of Cu and Fe there are greater strain mutation and intense stress concentration that is increased with particle diameter and the extent of deformation. This strain and stress concentration makes the interface initiate crack and develop crack easily. The micro-crack around the Fe particle is also attributed to surface flaking damage under the finish rolling deformation. The larger Fe particles should be avoided in the production of Cu-Fe-P alloy
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 475-479 (Jan. 2005), p. 3331-3334 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The aging process of lead frame Cu-Cr-Sn-Zn alloy has only been studied empirically by trial-and-error method so far. This paper builds up the prediction model of the aging properties via a supervised artificial neural network(ANN) to model the non-linear relationship between parameters of aging process with respect to hardness and electrical conductivity properties of the alloy. The improved model is developed by the Levenberg- Marquardt training algorithm. The predictedvalues of the ANN coincide with the tested data. So the ANN system is effective and successful for predicting and analyzing the properties of Cu-Cr-Sn-Zn alloy. The optimized processing parameters are available at 475 C ° -520 C ° aging for 2h-1h
    Type of Medium: Electronic Resource
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