Pure titanium and Ti6Al4V alloys with single-crystal Al2O3 rod cores were prepared at 1740 degrees C and 1.2 atm Ar for 30 min. Aluminium diffusion takes place from Al2O3 into the titanium region for both Ti/Al2O3 and Ti6Al4V/Al2O3 interaction couples and results in the formation of an ordered alpha(2) phase (Ti3Al) in the titanium region adjacent to interfaces, even though there is no visible interaction product at interfaces.