A stir casting method is one of the most competitive methods for fabricating SiC particle reinforced aluminum matrix composites because of its low cost with competitive quality. However, defects formed in the composites during the fabrication process will deteriorate their properties. Different kinds of defects such as black inclusions related to agglomerated SiC, silver spots related to Al-Fe-Si phases, white inclusions related to Al2O3 and porosity related to gas and SiC agglomeration are investigated in this paper. Based on these investigations, a technique for improving the quality of SiCp/A356 composites fabricated by a stir casting method is proposed. A SiCp/A356 composite with few defects and good properties was fabricated with the improved stir casting process.

Keywords: SiCp/A356 composites; stir casting; black inclusions; silver spots; white inclusions; porosity