Effect of Impurity Elements on Reaction of Reinforcement with Matrix in Rutile Type Titanium Oxide/Aluminum Composites

Abstract

The reactivity between titanium di-oxide and aluminum in aluminum alloy composites dispersed with rutile-type titania has been investigated by the thermal analysis and the morphological observation. The reaction of practical grade TiO₂/Al composites has proceeded by the heat-treatment at the solidus temperature of aluminum alloys, while the reaction has never occurred at the solidus temperature in the case of high purity TiO₂/Al composites. The difference of the reactivities between these composites at the solidus temperature is attributed to the effect of a small amount of Na which was one of the impurity elements in the practical grade TiO₂. Furthermore, the high purity TiO₂/Al composites doped with Na have shown an exothermic reaction at the solidus temperature. The difference between the morphology of Na doped TiO₂/Al composites heat-treated at the solidus temperature and that of high purity TiO₂/Al composites heat-treated at the liquidus temperature, suggests that the reaction mechanism between these cases is different. The apparent activation energy of the reaction at the solidus temperature has been estimated as 255.7 kJ/mol by calculating from the measurement of DSC. The present results suggest the possibility to control the reaction between inorganic materials and metals in the composites by the addition of small amount of an impurity element for the novel processing of composite materials.