Microstructures and mechanical properties of Ti3(Al,Si)C2/Al2O3 composites fabricated by current-assisted sintering of Ti3AlC2/SiO and Ti3AlC2/SiO2

Ti3SiC2/Al2O3 composites attract attention because Ti3SiC2 and Al2O3 have complementary advantages in me-chanical properties. However, the high temperatures (>= 1400 degrees C) required for densification of the Al2O3 lead to the decomposition of Ti3SiC2. To address this issue, Ti3(Al1-xSix)C2/Al2O3 composites were fabricated via current -assisted sintering of Ti3AlC2/SiO (TM sample) and Ti3AlC2/SiO2 (TD sample) at 1100-1300 degrees C. After sintering, most Al atoms in Ti3AlC2 were substituted by Si atoms, forming Ti3(Al1-xSix)C2 with values of x greater than 0.85. However, the morphologies of Al2O3 produced from Ti3AlC2/SiO and Ti3AlC2/SiO2 were different. Spherical Al2O3 produced by Al-Si substitution in SiO2 was difficult to densify at low temperatures, whereas the reaction between Ti3AlC2 and SiO disintegrated the matrix of SiO and produced dense Al2O3. As a result, the relative densities and mechanical properties of TM samples were less affected by a reduction in sintering temperature than those of TD samples. As sintering temperature declined from 1300 degrees C to 1100 degrees C, flexural strength, hardness, and fracture toughness of TM samples decreased by 35.9% (from 546.2 MPa to 350.0 MPa), 27.4% (from 4.56 GPa to 3.31 GPa), and 33.4% (from 7.45 MPa m0.5-4.96 MPa m0.5), respectively. Meanwhile, the flexural strength, hardness, and fracture toughness of TD samples were reduced by 81.2% (from 466.1 MPa to 87.6 MPa), 85.4% (from 6.50 GPa to 0.95 GPa), and 68.6% (from 6.94 MPa m0.5-2.18 MPa m0.5), respectively. Therefore, Ti3AlC2/SiO is more suitable for fabricating Ti3(Al1-xSix)C2/Al2O3 composites at low temperatures.