Titanium preconditioning of Al2O3 for liquid-state processing of Al-Al2O3 composite materials

Chemical vapor deposition (CVD) of titanium onto the surface of alumina substrates was used to improve the wetting by molten aluminum prior to infiltration. The CVD titanium coatings on alumina substrates were characterized by X-ray diffraction and energy-dispersive X-ray spectroscopy (EDS) as dual-phase, elemental titanium and titanium aluminide, Ti3Al. The kinetics of the coating process were quantified and analyzed using established reaction kinetics models. An overall activation energy of 219 kJ/mole was calculated for the formation of the titanium coatings on planar alumina substrates, for the temperature range of 610 degrees C to 870 degrees C. The CVD-coated planar and porous alumina substrates were immersed in molten aluminum, and wetting of planar substrates and infiltration of porous bodies were documented. Formation of both aluminum-rich and titanium-rich reaction products was observed through EDS cross-sectional analysis.