Microstructure and interface structure studies of SiCp-reinforced Al (6061) metal-matrix composites

The microstructure and interface structure of the particle reinforced 6061-Al metal-matrix composites have been studied by optical microscopy, transmission electron microscopy (TEM), high resolution electron microscopy (HREM) and energy dispersive X-ray spectroscopy (EDX). The SiC particles are uniformly distributed in the matrix. The constituent phase observed in the matrix is Al15(Mn,Fe,Cu)3Si2. It has a BCC structure with lattice parameter a=1.28 nm. The SiC reinforcements are found to contain hexagonal α-SiC (including 6Hα-SiC and 4Hα-SiC) and cubic β-SiC. Stacking faults are observed in the SiC particles. SiC reinforcements are well bonded with the matrix. In most cases, the interface between the SiC particles and the matrix is clean and no reaction product was observed. However, certain amount of oxygen and magnesium elements have been found at the interface. The reaction products at the interface are identified to be MgAl2O4 and MgO. The size of these particles are found to be of several nanometers.