Densification,Microstructure And Properties Of High Volume Fraction SiC_p/Al Composites

As a new type of electronic packaging materials,the high volume fraction SiCp/Al composites show many excellent characteristics such as low density,well thermal conductivity,and its controlled expansion coefficient.This material has been widely used in many fields such as aerospace,aircraft,automobile,electronics and military due to its mechanical and physical properties.In this paper,30%and 40%SiCp/Al composite were processed by powder metallurgy direct-route powder hot extrusion method.The micro-structures,mechanical properties and thermal properties in SiCp/Al composite materials with different content of SiCp particles are compared and analyzed by utilizing optical microscope(OM),scanning electron microscopy(SEM),tensile tester,brinell hardness tester,dilatometer and thermal-detector.The higher volume fraction SiCp/Al(50%～75%SiCp/Al)composite by hot-pressing process was aimed to explore the impact of silicon carbide volume fraction,the pressure and temperature on the material density during the hot-pressing process.Through the comparison of different process,acquire optimal process of different volume fraction SiCp/Al composite.The main results are as follows:(1)Different volume fraction SiCp/Al composite should be processed by different preparation process.For example,when the volume fraction of silicon carbide is less than 50%,hot extrusion forming process should be adopt;when the volume fraction of silicon carbide is not less than 50%,hot-pressing process should be employed.(2)The results showed that,with the increase of the volume fraction of SiCp particles added into SiCp/Al composite,the brinell hardness and thermal conductivity of SiCp/Al composite materials after hot extrusion improved;the compactness,ductility and coefficient of linear expansion reduced,while elongation decreased obviously.(3)50%～75%SiCp/Al composite was processed by hot-pressing process.The molding temperature and pressures are the two important factors to influence the material densification degree.As the hot-pressing temperature or pressure increased,the hole inside the material gradually reduced,the density was gradually improved.The material density reached to the highest when choosing an optimum process.As the hot-pressing temperature or pressure continued to increase,defects appeared again,densityalso began to decrease.Different volume fraction composite have different optimum hot-pressing process.(4)The volume fraction of SiCp particle has an important effect on the density of SiCp/Al composite.The density of the composite decreased with the volume fraction of SiCp particle increased from 50%to 75%.(5)The optimum hot pressing process of 50%SiCp/Al composite is as follows:620℃ pressing temperature,60MPa pressure.The optimum hot pressing process of 60%SiCp/Al composite is as follows:630℃ pressing temperature,50MPa pressure.