Production and characterization of composites of the Al-TiO2 system using the SHS process

Metallic matrix composites from Al and TiO2 powders were obtained to the weight proportions of Al - 5% TiO2, Al - 15% TiO2 and Al - 20% TiO2 using self propagating high temperature synthesis (SHS) process. The green samples were obtained with compaction pressures of 150, 200, 250 and 300MPa. The syntheses using a tubular furnace were carried out at 800, 900 and 1000 degreesC during 900 s. Helium atmosphere was maintained inside the furnace. Two kinds of coolings were employed: cooling inside the furnace and under helium flow of helium. The products were characterized by optical and scanning electron microscopy; microanalysis with EDS, X-ray diffraction, Vickers hardness and microhardness. The main phases characterized in the products were Al, alpha-Al2O3, non-reacted TiO2, Ti reduced, Al3Ti, AlTi, Al11Ti5, AlTi3 and Al5Ti3. As the synthesis temperature and non-reacted TiO2 amount in green samples were increased, it was observed an increase in the amounts of intermetallic and Al2O3 in the products. The hardness of the composites obtained was near the recrystalized aluminium hardness, 40 HV. The values of Vickers microhardness of the intermetallics confirmed the presence of the Al3Ti phase and others.