Abstract
Aluminum oxide must take a spinel form (
-Al2O3) at elevated temperatures in order for extensive
solid solution to form between MgAl2O4 and -Al2O3. The solvus line between MgAl2O4 and Al2O3
has been de ned at 79.6 wt% Al2O3 at 1500C, 83.0 wt% Al2O3 at 1600C, and 86.5 wt% Al2O3 at
1700C. A metastable region has been de ned at temperatures up to 1700C which could have signi cant
implications for material processing and properties. Additionally, initial processing could have major
implications on nal chemistry. The spinel solid solution region has been extended to form an in nite
solid solution with Al2O3 at elevated temperatures. A minimum in melting at 1975C and a chemistry
of 96 wt% Al2O3 rather than a eutectic is present, resulting in no eutectic crystal formation during
solidi cation.
