Morphology of spinels and Al2O3 particles in an Al2O3/Al-Mg-Si composite material revealed by scanning low energy electron microscopy

In metal matrix composite materials consisting of oxide particles and Al alloys, including Mg as a solute atom, MgAl2O4 spinels are formed at the interface between the particles and the matrix. In the present study, the scanning low energy electron microscopy (SLEEM) method has been applied to confirm morphologies of alpha-Al2O3 particles and MgAl2O4 spinet crystals grown on the alumina particles in the Al2O3/Al-1.0 mass% Mg2Si alloy composite material. The morphology of alpha-Al2O3 particles before fabrication of the composite material was like a facetted barrel with 2 hexagonal {0001} and 6 trapezoidal {(1) over bar 101} planes. Spinels were formed on facets of Al2O3 as small particles, and their shape was an octahedron consisting of 8 equiaxial triangles. Spinels and Al2O3 particles keep their orientation relationship which was concluded by our recent TEM study: (111)(MgAl2O4)//(0001)(Al2O3), [2 (1) over bar(1) over bar](MgAl2O4)//[2 (1) over bar(1) over bar0](Al2O3), [1 (1) over bar0](MgAl2O4)//[1 (1) over bar 00](Al2O3)