Microstructures and mechanical properties of in-situ Al2O3/TiAl composites by exothermic dispersion method

In-situ AhOz/TiAl composites were fabricated by près sure-assisted exothermic dispersion (PAXD) method from elemental powder mixtures of Ti, AI, TiO2, and Nb2O5 The micro structures and mechanical properties of the as-sintered composites are investigated. The results show that the as-sintered products consist of γ-TiAl, α2-Ti3 Al, Al2O3, and NbAl3 phases. Micro structure analysis indicates that Al2O3 particles tend to disperse on the grain boundaries. Application of a moderate pressure of 35 MPa at 1200°C yields Al2O3/TiAl composites with fine Al2O3 reinforcement and a discontinuous network linking by Al2O3 particles. The aluminide component has a fine submicron γ+α2 lamellar micro structure. With increasing Nb2O5 content, Al2O3 particles are dispersed uniformly in the matrix. The hardness of the composites increases gradually, and the bending strength and fracture toughness of the composites reach to the maximum value, respectively.