Theoretical and experimental study on settling of SiC particles in composite slurries of aluminum A356/SiC

In the present study settling of SiC particles in composite slurries of aluminum A356 alloy/SiC was investigated experimentally and the results were compared with theoretical predictions. The influence of size and volume fraction of SiC particles in different Al/SiC slurries together with thermal history during alloy solidification on the distribution of particles along the height of cylindrical composite samples was studied by image analysis of microstructures. In the theoretical part, the effect of particle shape, agglomeration of particles and hindered settling on the settling velocity of SiC particles was studied by using the Stokes equation with some relevant correction factors. It was found that by using the measured viscosity of slurries in the Stokes equation a good agreement between the experimental results and theoretical predictions could be obtained. A computer program was written using MATLAB software in which the Stokes equation was employed, and in addition to the above-mentioned correction factors, the collision and agglomeration of particles were also considered. This program was able to simulate reasonably accurately the settling of SiC particles in the solidifying alloy.