In-situ Al2O3/TiAl composites were prepared by hot-pressing method based on the exothermic reaction of Ti-Al-TiO2-Nb2O5 system.Effects of Nb2O5 addition on microstructure and mechanical properties of the prepared composites were investigated by SEM（scanning electron microscope）

XRD（X-ray diffraction）.The results indicate that the as-sintered composites consist of γ-TiAl

α2-Ti3Al

Al2O3 phase and NbAl3 phase.With increasing in Nb2O5 content

the density

relative density and hardness of the composites are gradually increased

meanwhile

bending strength and fracture toughness are firstly increased and then decreased

in which the maximum values are 398.5 MPa and 6.99 MPa·m1/2

respectively

with 6% Nb2O5 content.Microstructure analysis shows that

sintered at 1200℃

the composites present a γ+α2 lamellar structure.With Nb2O5 content increase

the aggregate degree of Al2O3 particles is improved with dispersively distributed along the grain boundary

meanwhile

the dual-phase γ+α2 lamellar structure is refined with more homogeneous distribution.Nb2O5 additive plays an important role in adjusting phase content and refining structure

which is beneficial to improving the properties of the composites.