Microstructure development and properties of alumina–Ti aluminide interpenetrating composites

Abstract

Interpenetrating phase Al₂O₃–Ti₃Al composites have been fabricated by reaction sintering of 2 and 4-h discus milled composite powders containing Al and TiO₂ using controlled heat-treatment in non-oxidizing atmospheres. Pressureless sintering and hot pressing of the powders has been carried out under vacuum and argon at temperatures between 1278 °C and 1500 °C and a heating rate of 5 °C/min. Densification of the composites was investigated as a function of temperature. It was shown that lower porosity was obtained by hot pressing compared to pressureless sintering.

The microstructure development and mechanical properties of dense Al₂O₃–Ti₃Al composites fabricated by hot pressing of Al–TiO₂ powder blends were examined. Fully dense microstructures could be achieved by hot pressing at 1387 °C under vacuum. An increase of Vickers hardness was observed with increasing temperature, which can be attributed to the increase of density and the decrease in the level of porosity of the composites. The mechanical behaviour exhibited by the composites can be related to properties such as Al₂O₃ particle size and porosity level. Fracture toughness of 6.3 ± 0.8 MPa m1/2 and Vickers hardness of 13.6 ± 0.4 GPa were achieved for the fully dense composite produced by hot pressing discus milled powder.