THE SYNTHESIS OF TIB2-TIAL3 COMPOSITES BY FIELD-ACTIVATED COMBUSTION

The synthesis of TiB2-TiAl3 composites with TiB2/TiAl3 = x molar ratio s from x = 1.0 to 5.0 were investigated by electric field-activated co mbustion using elemental powders as reactants. Using amorphous boron p owders, composites with x less than or equal to 2.0 can be synthesized in the absence of a field. Those with 3.0 less than or equal to x les s than or equal to 5.0 can only be formed in the presence of a field. For all cases, the product contained the desired phases with minor amo unts of Ti5Al11. Higher values of x, resulted in relatively higher amo unts of this phase. The effect of the use of crystalline boron and the influence of its particle size were also investigated. In the absence of a field, no self-sustaining combustion wave could be initiated eve n when the smallest particles (< 20 mu m) were used. Under the influen ce of an 18 Vcm(-1) field, combustion waves were initiated and the pro ducts were virtually identical to those obtained with the amorphous bo ron powders. (C) 1998 Elsevier Science S.A. All rights reserved.