Effect of the Stirring Velocity and the SiO2 Precursor Particles Feeding Rate on the Microstructure of the Al2O3/SiO2/Al Composites Prepared via Stir Casting Process

Stir casting has been taken as a low cost and effective way to disperse ceramic particles in molten alloys and obtain the high-performance metal matrix composites. However, the reinforcement precursors with a similar density to the molten aluminum are difficult to be uniformly dispersed in the melts. Herein, the particulate quartz, which can react with the aluminum melts and form the Al2O3/SiO2 reinforcement, is used as the reinforcement precursor. Effect of the stirring speeds of the melts and the feeding rates of precursor particles on the reinforcement distribution in aluminum matrix are investigated. The numerical simulation is carried out to analyze the particles dispersion course in the melts. Results show that the precursor particles in molten aluminum achieve a relatively uniform dispersion at the modest stirring rate of 400 rpm. Meanwhile, numerical simulation results also prove that precursor particles will distribute homogenously in the Al matrix while exerting the stirring rate at 400 rpm. From the microstructure of the composites, it is evident that extremely high stirring rate and particles feeding rate will lead to the agglomeration of particles, which is not favorable to the composites performance.