Mechanical activation of the formation of an alumina-titanium trialuminide composite

The fabrication of a powder composed of alumina and titanium trialuminide TiAl₃ from TiO₂ and aluminium powder is reported in this paper. The powders were ball-milled together under vacuum for 100 h in a laboratory scale mill with no reaction evident directly after milling. Differential thermal analysis showed that the milled powder underwent an exothermic reaction below the melting point of aluminium. An unmilled powder underwent a slow reaction until an exothermic reaction occurred at 1000°C. The milled powder showed complete reaction to Al₂O₃ and TiAl₃ after heating to 600°C whereas the unmilled powder reaction was incomplete after 1 h at 1200°C. Analysis of the energetics of the reactions suggested that the milled powder would undergo self-propagation, whereas the unmilled powder would not.