The effect of AlN whiskers addition on pressureless sintering behavior of ZrB2-SiC composite

ZrB2 base composites containing SiC, MoSi2 and AlN have good sinterability and mechanical properties. In this study, 20 vol% nanometric SiC and 4wt% micrometric MoSi2 with different amount of AlN whiskers (0-10%vol) added to ZrB2. After mixing, composite samples were formed by cold isostatic press (CIP) with 200MPa pressure, and then samples were fired at 2100°C/1hr in Ar atmosphere with heating rate of 10°C/min. After firing bulk density, open porosity, microhardness, toughness, microstructural and phase analysis were determined. The results showed that optimum properties obtained at 7.5%vol AlN whiskers with relative density (96.3%), open porosity (1%vol), Vickers hardness (18.5 GPa) and fracture toughness (4.37 MPa.1/2). The SEM+EDS and XRD analysis showed that SiC and AlN solid solution and formation of Zr2Al3C4 phases due to probably high vapour pressure of AlN at 2100°C were promoted sintering and improvement of properties of composites.