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

The fabrication of a powder composed of alumina and titanium trialuminide TiAl(3) from TiO(2) and aluminium powder is reported in this paper. The powders were ball-milled together under vacuum for 100h 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 degrees C. The milled powder showed complete reaction to Al(2)O(3) and TiAl(3) after heating to 600 degrees C whereas the unmilled powder reaction was incomplete after 1 h at 1200 degrees C. Analysis of the energetics of the reactions suggested that the milled powder would undergo self-propagation, whereas the unmilled powder would not. (C) 1998 Published by Elsevier Science Limited. All rights reserved.