Effects Of Alumina Sintering Aid On The Physical Properties Of SiC_p/Al Composite Material

As the electronic packing material,silicon carbide reinforced aluminum composite is favored by many researchers because of its high thermal conductivity,high strength,low thermal expansion coefficient,low density and many other excellent properties.Pressureless infiltration technique is an effective method to prepare high-volume ratio SiC composite materials with advantages of preparation process is simple and process can be near-net-shape.The study on pressureless infiltration preparation processes and principles of SiC_P/Al composites is fairly mature,but its industrial production scale in home is small and the properties of producted composites are inferior to that of abroad.Therefore,further researches on the subjects are necessary to promote them.In this paper,Al₂O₃ sintering aid was added to improve the binding of SiC particles,and its effects on raw material handling,preparation of preforms,infiltration temperature,infiltration time,interface reaction and properties of composite materials were studied by using of Scanning Electron Microscope?SEM?,Energy Dispersion Spectrometer?EDS?,X-Ray Diffraction?XRD?and other techniques.The main focus is as follows:?1?Removal effict of the impurities among and on the oxide layer of SiC raw powders by mixed acid?HF,HCl?was studied;the cleaned Si C particles were oxidized in oxygen at 1600? and treated in nitrogen at 2050?;the blunting on SiC particles was analysed;the preoxidation can generate a dense cristobalite layer on the surface of SiC particles;a self-designed spray drying equipment was used to and can mix the preprocessed Si C powder with added submicron Al₂O₃ particles and binding agent evenly and no clear agglomeration can be observed.?2?The effects of adding amount of PVA,pressing pressure and sintering temperature on the forming,porosity and strength of preform were studied.The results showed that adding PVA had a significant effect to the prepartion of preform;pressing pressure and sintering temperature had a significant effect to porosity;and the formation of mullite on interface can improvegreatly the strength of preform.?3?The effects of adding amount of Al₂O₃,preform sintering time,infiltration temperature and time on the bending strength and thermal conductivity of SiC_P/Al composite were investigated through orthogonal experiments.The results showed that proper addition of Al₂O₃ can significantly increase the bending strength,but has little effect on the thermal conductivity of the composite.The optimal bending strength of 344 MPa and thermal conductivity of 165 W·m-1·K-1 were obtained under the conditions of adding 2.0 at% Al₂O₃,2 h preform sintering time,1400? preform sintering temperature,950? infiltration temperature and 1 h infiltration time.Besides,the formation of mullite on the interface of composite can effectively prevent the occuring of harmful Al4C3.Finally,on the basis of the whole experimental results,some suggestions have been proposed for the industrialized production of SiC_P/Al composite materials by pressureless infiltration,which may give some technical support and experimental evidence to the industrialized production at home.