Effects of Pr6O11 on the microstructure and mechanical properties of Ti/Al2O3 composites prepared by pressureless sintering

Ti/Al2O3 composites with different volume percentages of Pr6O11 added (0-12.0  vol.%) were prepared by pressureless sintering at 1600 °C for 1.5 h. The influences of Pr6O11 on the composition, microstructure and mechanical properties of the composites were characterized and investigated. The results showed that Pr6O11 could promote the sintering of the composites by generating some new interfacial reaction products, such as AlTiO2, Pr2Ti2O7 and PrAlO3. Pr6O11 could also inhibit the production of TiAl and Ti3Al by the same mechanism. Additionally, Pr6O11 changed hexagonal alumina to tetragonal alumina. The latter could improve the mechanical properties of the composites by the effects of crack deflection and particle pullout when it was present in proper amounts. Composites showed satisfactory comprehensive properties when the content of Pr6O11 was no more than 3.0 vol.%.