Mechanical properties and fracture behavior of B4C-nano/micro SiC composites produced by pressureless sintering

In the present work, boron carbide (B4C) powder was mixed separately with various quantities (2.5, 5, 7.5 and 10 vol%) of nano/micro silicon carbide (nano/micro SiC) in a high-energy mill and in the presence of isopropanol solution. The resulting compounds were then dried and formed into test specimens at a pressure of 80 MPa. Next, using the pressureless sintering technique, the obtained pieces were sintered at temperatures of 2100, 2150 and 2200 °C. The effects of additives and sintering temperature on the grain size and mechanical properties of the produced specimens (e.g. flexural strength and fracture toughness (KIC)) were studied, and the fracture behavior of these samples was evaluated through microstructural analysis. By adding nano/micro SiC, the results indicate a considerable increase in the flexural strength (up to 860 MPa) and KIC value (up to 6 MPa m1/2) of specimens. Also, it was found that by increasing the vol% of nano/microSiC additive, not only the produced composites become fine-grained, but also their fracture mode changes mostly from intergranular to transgranular.