Interfacial microstructure evolution in aluminium matrix composites reinforced with unoxidized and oxidized SiC particles

Interfacial microstructure evolution of Al matrix composites with non-oxidized and oxidized SiC particles as reinforcement was investigated using x-ray diffraction, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Hexagonal platelet-shaped Al4C3 and Si are the two major interfacial reaction products in the non-oxidized SiC-particle-reinforced Al matrix composites (SiCp/Al). In addition, the eutectic θ-CuAl2 and Si phases precipitate at the SiCp/matrix interface during the last solidification stage. Observation of the interfacial reaction between the oxidized SiC particles and Al alloy containing Mg shows that the SiO2 layer has good bonding with both SiC and Al matrix and that nanoparticles of MgO have formed initially. The MgO particles will change into octahedral MgAl2O4 crystals when there is a low Mg content in the matrix (≤2 wt.%) and will remain as MgO when there is a high Mg content (≥4 wt.%). Copyright © 2001 John Wiley & Sons, Ltd.