| SiCp/Al composites have important potentials in the area of power electronics,due to their excellent properties such as high specific strength,specific stiffness and thermal conductivity（TC）and low thermal expansion coefficient（CTE）and density.Studies on preparation of the mid-/high-fraction SiCp/Al electronic packaging composites via pressureless sintering and/or hot pressing sintering are more important in developing a low-cost fabrication technology and further expanding the application areas of the composites.In this study,the elutriated F500-SiC powder was blended with the 6061Al alloy powder of an average particle size of 15 um at a volume ratio of 30:70,and then mixed in a double-roller mixer.After adding 1-2 wt%wax plasticizer,the 30 vol%SiCp/6061Al composite powder was compacted under 600 MPa and finally sintered at 660-700℃.The elutriated F500-SiC powder was also blended with the 6061Al alloy powder of an average particle size of 15 um at a volume ratio of 50:50,and then mixed in a double-roller mixer.The mixture powder was filled into a graphite mold,and hot-pressed at 660-700℃in vacuum under 25 MPa to fabricate the 50 vol%SiCp/6061Al composites.Based on studies on microstructure and properties of the composites,the powder metallurgy process of the mid-/high-fraction SiCp/6061 Al matrix composites was optimized.Finally,the mid-/high-fraction SiCp/6061Al composites of excellent microstructures and mechanical/thermo-physical properties were well developed.Density,bending strength and TC of the 30 vol%SiCp/6061Al composites increase initially and then decrease as increasing the sintering temperature.In the 680℃sintered 30 vol%SiCp/6061Al composites,the SiC particles distribute uniformly without any aggregation and have an intensive interfacial bonding with the Al alloy matrix.In the fracture process of the composites,the cleavage of the SiC particles and the dimple-agregation toughness fracture of the Al alloy matrix take place.As a result,the composites also have the best properties,i.e.the relative density of 98.2%,the bending strength of 426 MPa,the TC of 159 W/（m·K）and the CTE of12.5×10-6/℃（20-100℃）,respectively.Density,bending strength and TC of the 50vol%SiCp/6061Al composites also increase initially and then decrease as increasing the sintering temperature.During hot pressing,the fluidity of the Al alloy is promoted by the applied loading.So,the Al alloy can fill up the gaps among the SiC particles.Hot-pressing of the composites can be filfulled at lower temperature than the pressureless sintering of them,as a result,the SiCp/Al interfacial reaction is apparently inhibited,and also high properties of the composites are achieved.The properties of the 630℃hot-pressed 50 vol%SiCp/6061Al composites are:the relative density as high as 98.6%,the bending strength of 332 MPa,the TC of 186 W/（m·K）and the CTE of 7.9×10-6/℃（20-100℃）,respectively.The fracture mode of the composites is of cleavage of the SiC particles and plastic tearing of the Al alloy matrix,meaning a high SiCp/Al interfacial bonding strength. |
