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

Abstract

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.