Preparation and property evaluation of TiB2 + TiSi2 composite

This paper reports on the densification of TiB2 by hot pressing using TiSi2 as an additive. Mechanical, physical and thermal properties of the dense pellets were evaluated Isothermal oxidation studies were. carried out at 850 degrees C for selected samples. Microstructural studies of hot pressed and oxidized samples were carried out using SEM, EPMA and XRD. High density pellets of >96% rho(th) were obtained by hot pressing of the powder mixtures at 1550 degrees C and a pressure of 30 MPa. Ti5Si3 phase was identified as a reaction product of hot pressing. Hardness values of the composite with varying TiSi2 were measured to be in the range of 18-25 GPa. Fracture toughness was marginally higher in the range of 4-6 MPa m(1/2) compared to 3-4 MPa m(1/2) for monolithic TiB2. Flexural strength of the composite with 2.5%TiSi2 Was measured as 400 MPa. Coefficient of thermal expansion and electrical resistivity were measured up to 800 degrees C. Improved oxidation behavior was observed in the TiB2 + TiSi2 composite compared with TiB2 + MoSi2 composite. TiO2 and SiO2 phases were identified on the surface of the oxidized samples. (C) 2008 Elsevier Ltd. All rights reserved.