Effects of TiO2/Al ratio on microstructures and mechanical properties of TiAl base composites

Effects of TiO2/Al ratio on the microstructures and mechanical properties of in situ Al2O3/TiAl based composites were investigated. The results indicate that the as-sintered products consist of grains of nearly lamellar α2 + γ structure with a dispersion of randomly oriented Al2O3 particles. A 43.9Ti-38.6Al-17.5TiO2-nNb2O5 system was compared to 57.46Ti-36.78Al-5.76TiO2-nNb2O5 system. The lamellar spacing of the products increases and the α2 phase volume decreases with decreasing TiO2/Al ratio. For each system, as the volume of α2 phase increases, the average lamellar spacing decreases. Strength increases with an increasing TiO2/Al ratio due to the amount of α2 phase. Al 2O3 phase increases with increasing TiO2/Al ratio. Toughness increases with decreasing TiO2/Al ratio. When the Nb2O5 content is smaller than 6 wt.%, the lamellar spacing plays an important role in toughness than the Al2O3 content. When the Nb2O5 content is larger than 6 wt.%, the Al2O3 content exhibits significantly increases the values of toughness than lamellar spacing. © 2008 Higher Education Press and Springer-Verlag GmbH.