The crystallographic orientation relationship between Al2O3 and MgAl2O4 in the composite material Al2O3/Al–Mg–Si alloy

The formation mechanism of spinels on Al2O3 particles in the Al2O3/Al–1.0 mass% Mg2Si alloy composite material has been investigated by transmission electron microscopy (TEM) in order to determine the crystallographic orientation relationship. A thin sample of the Al2O3/Al–Mg–Si alloy composite material was obtained by the FIB method, and the orientation relationship between Al2O3 and MgAl2O4, which was formed on the surface of Al2O3 particles, was discovered by the TEM technique as follows: $$ \left\{ {111} \right\}_{{\text{MgAl}}_{\text{2}} {\text{O}}_{\text{4}} } //\left\{ {0001} \right\}_{{\text{Al}}_{\text{2}} {\text{O}}_{\text{3}} } $$ $$ \left[ {2\bar 1\bar 1} \right]_{{\text{MgAl}}_{\text{2}} {\text{O}}_{\text{4}} } //\left[ {2\bar 1\bar 10} \right]_{{\text{Al}}_{\text{2}} {\text{O}}_{\text{3}} } ,\left[ {1\bar 10} \right]_{{\text{MgAl}}_{\text{2}} {\text{O}}_{\text{4}} } //\left[ {1\bar 100} \right]_{{\text{Al}}_{\text{2}} {\text{O}}_{\text{3}} } $$ At the interface between the Al2O3 and the matrix the MgAl2O4 (spinel) crystals had facets of {111} planes. Spinels were not grown as thin films, but as particles consisting of {111} planes. They grow towards both the matrix and the Al2O3 particles.