Investigation on microstructure, mechanical properties and pressureless sintering behavior of ZrB2-SiCnano/micron composites toughened by AlN

In the present paper, ZrB2-SiC was developed by pressureless sintering method and SiC powder at nano and micro-sized scale was used as reinforcement phase. AlN was added to this composite from 2.5 to 15 vol.% as sintering aid. In order to produce composite samples, the primary powders were milled and blended in planetary ball mill apparatus with rotational speed of 200rpm and then processed using uniaxial press (70ᵒC and 70MPa), cold isostatic press (200MPa), Pyrolysis (1000ᵒC) and sintering (2150ᵒC). The values of relative density and porosity of samples were measured to evaluate the effect of presence of micro-sized SiC and SiC nano particles simultaneously on the pressureless sintering behavior of ZrB2-SiC. In order to compare the microstructure and mechanical properties of samples Scanning Electron microscopy (SEM), equipped with EDS spectroscopy, XRD analysis, hardness and toughness tests were used. The results show that as the volume percentage of nano SiC decreases to 15 vol.% and AlN increases to 7.5 vol.% the hardness, toughness, relative density and shrinkage initially increase and then decrease