Influence of Y2O3 addition on the Ti/Al2O3 cermets by hot pressing sintering

The Ti/Al2O3 composites are fabricated by hot pressing sintering, and the effect of Y2O3 on the microstructure and mechanical property of Ti/Al2O3 composites has been studied by means of SEM, EDS and XRD. The results show that the Al2O3 decomposition to Al and O first, and then Al diffusion to Ti formed the intermetallics such as Ti3Al and TiAl phases in the composites. Thermodynamics calculation shows us the Gibbs free energy are −120.23 kJ/mol and −73.44 kJ/mol for Ti3Al phase and TiAl phase, respectively. The addition of yttria to the composites makes enthalpy changes, reduces the amount of Ti3Al phase. The effect of Y2O3 addition on the microstructures and mechanical properties of the Ti/Al2O3 composite was characterized. When the Y2O3 content is 1.0 vol%, the flexural strength, fracture toughness, Vickers hardness and relative density of the composite reach the maximum values of 302.73 MPa, 6.45 MPa m−1/2, 16.78 GPa and 98.63%, respectively, and the fracture mode changes from intergranular to transgranular.