Effects of Y2O3 on the mechanical properties of Ti/Al2O3 composites of hot pressing sintering

Ti/Al2O3 composites with Y2O3 additions varied from 0 vol.% to 1.5 vol.% were fabricated by vacuum hot pressing sintering and the effect of Y2O3 additions on the mechanical properties of the composites was investigated. The composite with 1.0 vol.% Y2O3 addition showed superior density (relative density of 97.46%), hardness (micro-hardness of 13.34 GPa), strength (flexural strength of 488.08 MPa) and toughness (fracture toughness of 8.15 MPa m1/2) when sintered at 1450 °C for 30 min under the pressure of 30 MPa. It can be seen from the SEM images that the fracture mode of the Ti/Al2O3 composites has changed from the intergranular fracture into a mixture of intergranular and transgranular fracture with the addition of Y2O3. The mechanism of that was confirmed as the inhibition of the interfacial reactions between Ti and Al2O3. However, excessive Y2O3 additions (>1.0 vol.%) would greatly reduce the yield of Ti-Al intermetallic compounds, which weakened the “pinning effect” caused by the compounds, and finally degraded the mechanical properties of the composites.