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High volume fraction SiCp / Al composites , tensile deformation and blackening treatment studies

Author: LuoSiJun
Tutor: ChenKangHua
School: Central South University
Course: Materials Science
Keywords: high volume fraction SiCp/Al composite perform tensile behavior blackening
CLC: TB33
Type: Master's thesis
Year: 2009
Downloads: 69
Quote: 1
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Abstract


There are broad applicating prospects to High volume fraction SiCp/Al composites in the fields of space optics and precision instruments for its high performances as such as high thermal conductivity, low thermal expansion coefficient, higher elastic modulus, et al. To apply the composites to structural components of space optics machines, in this dissertation it is studied that infiltration composite preparation, the tensile behavior and the surface blackening of the composites.Compression and tensile test and SEM are made use to investigate the effects on compressive strength of SiCp performs, mechanical performances and microstructure of the composites with preoxidating performs and joining metaphosphoric acid aluminum into performs as binder. It is also studied that the effects on quench cracking of the composites with different quench processes. Compressive strength of SiCp performs and tensile strength of the composites are increasing as both oxidation increatment of SiCp in preoxidation and increased content of metaphosphoric acid aluminum, but tensile strength of the composites will decline when preoxidating temperature exceeds 1000℃or the content of metaphosphoric acid aluminum exceeds 2%. It can be solved that large size of the composites quenched cracking when using oil as a quenching medium and appropriately increasing the oil temperature.The effects of thermal cycling, preloading and metaphosphoric acid aluminum joined into SiCp preforms on tensile deformation behavior and microstructure of 55vol% SiCp/AI-10Si-0.7Mg composites prepared by pressure infiltration are studied through tensile testing and SEM. Study shows that heat treatments and preloading have less influence on elastic modulus of the composites, of which the tensile elastic limit can be improve by them. Joining metaphosphoric acid aluminum into SiCp performs is able to improve both elastic modulus and tensile elastic limit of the composites.Sulfuric acid anodic oxidation-chemical blackening on the surface of high volume fraction SiCp/Al composites is studied through metallographic microscope, SEM, three-dimensional video microscopy, XRD analysis and measuring reflectivity. Sulfuric acid anodic oxidation makes the surface of the composites form three morphologies and structures:A12O3 porous anodic oxidation film, exposed surface of the SiC particles, rough and uneven surface around SiC. Chemical blackening process is as follows:solution of a chemical reaction to generate the black MnO2 and Co3O4 sediments deposites on the three structures, a layer of black film is formed on the surface of the composites. Optimizing process parameters through the orthogonal experiment, the absorption rate of the blackened surface of high volume fraction SiCp/Al composite material to visible light with 430-700nm wavelength is over 90%.

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CLC: > Industrial Technology > General industrial technology > Materials science and engineering > Composite materials
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