Crystallography of SiC/MgAl2O4/Al interfaces in a pre-oxidized SiC reinforced SiC/Al composite

A transmission electron microscopy study has been performed on the crystallography of SiC/MgAl2O4/Al interfaces in a pre-oxidized SiC particulate reinforced SiC/Al composite prepared by pressureless infiltration, with a reactant of spinel MgAl2O4 phase at the SiC/Al interface. Four types of different orientation relationships (ORs) were observed between the 6H (alpha)-SiC and the MgAl2O4 spinel phase, with the SiC(0 0 0 1) parallel or {0 1 1 2}near parallel to the spinel {1 1 1}. Moreover, the cubic 3C (beta)-SiC and the spinel phase MgAl2O4 exhibited a parallel OR, while the MgAl2O4 and Al matrix had a semicoherent interface without a certain OR, except of the near parallel OR for some spinel particles. The observed ORs were analyzed using a geometric method based upon the coincidence of reciprocal lattice points. Possible ORs of other SiC polytypes with the spinel MgAl2O4 phase were also discussed.