Preparation And Characterization Of High Stiffness And Lightweight Al/SiC Materials

High stiffness and lightweight Al/SiC materials have the properties of low density, high strength and high thermal conductivity to attract the attention of aerospace materials. At present, the report of high stiffness and lightweight Al/SiC based composites is less. by changing the preparation have been employed to manufacture the Al/SiC based composite material with high volume fraction, its density and resistance compressive strength are improved.In this work, high purity SiC powders were synthesized by carbothermal reduction method using diatomite and activated carbon as raw material, and the main factors were carbon content, the amount of catalyst content, the heating temperatures and different holding time which were analyzed. Where the temperature and holding time on the yield of SiC in the larger, the higher the temperature, the longer the holding time, the higher production rate of SiC. The carbon content also has some influence on the yield of SiC, the greater the content with carbon, The higher production rate, when this molar ratio exceeding 1:5, the yield of SiC is almost constant. Fe2O3 can be added to the feed to accelerate the reaction, but the content of Fe2O3 is added more than 3%, will be reduced of SiC generation rate. By orthogonal experiment predicted optimum temperature of 1500 ℃, holding time of 5h, with carbon ratio of 1:6, the catalyst content of 3%. The production rate of SiC powder is 92.85% in optimal process. Then using powder metallurgy method and spark plasma sintering to prepare high volume fraction of Al/SiC alloy matrix composites(70 vol.%).The composites have been investigated by Metallographic analysis and mechanical properties. The major conlusion is introduced as follows:Particles can increase the ratio of SiC powder bulk density and improve the Al/SiC matrix composites density. PM prepared Al/SiC matrix composites density of about 90%, and enhance the relative distribution of agglomeration, the interface is no obvious holes, through XRD phase analysis found the interface appear Al4C3 which is brittle phase, particle size ratio of Al/SiC composites the compressive strength of the material is higher than the single particle size of SiC reinforced aluminum matrix composites. Al/SiC alloy matrix composites(70vol.%) could be obtained with SPS technical at 600 ℃, the density reaches 92.4%. Si alloying elements increase the fluidity of the alloy in the molten state, reducing the surface tension of the interface of the composite material, to improve the wettability between SiC and Al matrix. And suppresses the generation of brittle phase Al4C3 improved microstructure and mechanical properties of the composites. Mg alloy element to improve the Al/SiC composites wettability, generate MgAl2O4 phase avoid brittle phase Al4C3 generation, while adding Mg improved the Al/SiC composites density.