Vortex-free stir casting of Al-1.5 wt% Si-SiC composite

Abstract

This paper investigates the avoiding of air entrapment and the quick realizing of uniform distribution of SiC particles in stir-casting Al-1.5 wt% SiSiC composite by vortex-free stir casting (VFSC). The air entrapment can be completely avoided by vortex-free high-speed electromagnetic-mechanical stirring and the porosity of composite can be reduced from about 3 vol% to less than 0.04 vol%. Meanwhile, the uniform distribution of SiC particles in the Al-1.5 wt% Si slurry can be quick realized in the crucible with tilt blades by adjusting the horizontally and radially tilt angles of blade. In addition, the primary Al particles and the high viscosity of slurry can restrain the settling of SiC particles and maintain the uniform distribution of SiC particles during casting in metal mold. The microstructure and composition of composite are determined by SEM, XRD, TEM and HRTEM. The (020) plane of Al is parallel to the (1¯103) plane of 6H α-SiC and their 0.053 nm lattice misfit results in a semi-coherent and clean interface. The compact, homogeneous and well-combined VFSC Al-1.5 wt% SiSiC composite possesses outstanding performance. The tensile strength of Al-1.5 wt% Si matrix can be increased 64.9%, the hardness can be enhanced from 60 to 78 BHN and the wear rate can be reduced 92.4% by 8 vol% SiC particles. This investigation provides a quick stir-casting mode for advanced AlSiC composite.