Microstructure and mechanical behavior of ternary phase ZrB2-SiC-AlN nanocomposite

The ZrB2-SiC nano composite was produced in a pressureless sintering method. The micro AlN powder was used as an additive. In order to investigate the effect of the simultaneous presence of nano and micro particles of SiC, the ZrB2 powder with various percentages of nano and micro SiC particles were mechanically milled in a planetary mill for 2 h at a speed of 200 rpm. The resulting mixture was subjected to an initial hot press at 80 °C and a pressure of 100 MPa and then cold isostatic pressing was done (CIP) and the resulting sample sintered at 2150 °C. The AlN particles were then added to ZrB2-SiC composite and its microstructure and mechanical properties were evaluated. The results show that by changing the volume percentage of nano SiC particles from 20% to 15% and 5% for the micro particles, the porosity decreases and the density increases. Microstructural analysis and mechanical properties of the samples showed the highest hardness (15.9 GPa) and fracture toughness (4.9 MPa.m1/2) for the sample with 15 and 5 vol% of nano and micro SiC particles respectively. Addition of 7.5 vol% of AlN particles resulted to the density of 98.1% and the hardness and toughness values increased to 17.1 GPa and 5.7 MPa.m1/2.