Air-isolated stir casting of homogeneous Al-SiC composite with no air entrapment and Al4C3

An air-isolated stir casting (AISC) technology was developed to solve the problems of air entrapment, inhomogeneous distribution of SiC particles and formation of weak compound Al4C3 in conventional stir casting of Al-SiC composite. To eliminate the air entrapment, a threaded cover screwed into the threaded crucible was used to evacuate the air in the crucible and a sealing plug on the cover was applied to isolate the Al-SiC slurry from the atmosphere. To realize the homogeneous distribution of SiC particles rapidly, a high-speed electromagnetic stirring was carried out to stir the Al-SiC slurry with the help of three uniform-distributed tilt blades on the crucible inner wall. Furthermore, the primary solid Al particles and the high viscosity of slurry were utilized to restrain the settling of SiC particles during casting. To avoid the formation of Al4C3 under short stirring time, the stirring temperature was dropped below 650 degrees C. The theoretical analysis and the results of SEM, XRD, TEM and HRTEM show that the homogeneous Al-SiC composite with no air entrapment and Al4C3 can be processed by AISC technology. The mechanical and wear results and mechanism analysis show that the AISC Al-SiC composite possesses excellent performances.