Research On The Semi-solid Forming Of Box Part Of High Volume Frachtion SiC_p/Al Composites

As a new type of electronic packaging materials，the high volume fraction SiCp/Alcomposites have the advantages of high thermal conductivity, low thermal expansionand low density which meet the requirements of aerospace for electronic packagingmaterials. What’s more, the heat physical properties can be designed by changing thecomposition and content to carry out the purpose we want and the raw material costs arevery low. This study will use the technique of semi-solid for composites to research thenet shaping of the thin-walled rectangular box made from high volume fraction ofSiCp/Al composites and analysis the effects of process parameters on the properties ofthe material to get the best technology parameters.The main body of the study includes: SiC powder is pretreated to improve thewettability between the ceramic particles and metal substrate; four kinds of SiC volumefraction such as45%,50%,55%and60%are made to research the impact of SiC volumefraction on the properties of composites; Semi-solid preform bodies are made throughpowder mix, normal temperature pressing and high temperature pressing; Thethin-walled rectangular boxes are made by remelting the preform bodies and semi-solidforming and the influences of process parameters on the formability and microstructureare studied; Finally the density, mechanical properties, thermal conductivity propertiesand thermal expansion properties of the materials are tested and the influences ofprocess parameters on them are studied.The SiC powder is pretreated by acid pickling, drying and high-temperatureoxidation to remove impurities and produce SiO2oxidation on the surface of SiC and byadding the third kind metal element Mg to improve the wettability of the interfaceinside SiCp/Al composites. The normal temperature preform bodies can be madesuccessfully by reasonable mold design and lubrication of die wall without adding anyother binder. And the through high temperature pressing we can get the semi-solidpreform bodies which have fine density, uniform microstructure and three-dimensionalconnecting Al matrix network. Finally, through reheating melting and semi-solidforming we can get different SiC volume fraction of SiCp/Al composites which aremade from different processing parameters. Then the paper studied the influence of thevolume fraction of SiC, forming temperature, mold temperature and forming pressureon the formability, density, mechanical properties, thermal conductivity and thermalexpansion of the composites and also study the physical theory model ofthermo-physical properties. After the study, relative influence laws are got: The density,flexural strength, thermal conductivity and thermal expansion coefficient of the material decrease with the increasing of SiC volume fraction; the density, flexural strength andthermal conductivity increase with the increasing of forming temperature, moldtemperature and forming pressure while the thermal expansion coefficient decreases.Through comparison and analysis we got the best SiC rate and process parameterswhich can produce materials that meet the requirements of electronic packaging well:55%the SiC volume fraction,720℃forming temperature,350℃mold temperatureand1600kN forming pressure. Using such processing parameters, we can get the55.vol%SiCp/Al composites with the density of98.9, flexural strength of257MPa,-1K-1-6K-1。...