Effects of Y_2O_3 on the mechanical properties of Ti/Al_2O_3 composites of hot pressing sintering

摘要

Ti/Al_2O_3 composites with Y_2O_3 additions varied from 0 vol.% to 1.5 vol.% were fabricated by vacuum hot pressing sintering and the effect of Y_2O_3 additions on the mechanical properties of the composites was investigated. The composite with 1.0 vol.% Y_2O_3 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 m~(1/2)) when sintered at 1450 ℃ for 30 min under the pressure of 30 MPa. It can be seen from the SEM images that the fracture mode of the Ti/Al_2O_3 composites has changed from the intergranular fracture into a mixture of intergranular and transgranular fracture with the addition of Y_2O_3. The mechanism of that was confirmed as the inhibition of the interfacial reactions between Ti and Al_2O_3. However, excessive Y_2O_3 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.