Improvement of mechanical properties of HfB2-based composites by incorporating in situ SiC reinforcement through pressureless sintering
S. Ghadami, E. Taheri-Nassaj, H. R. Baharvandi, Farzin Ghadami
Abstract
Abstract HfB 2 , Si, and activated carbon powders were selected to fabricate 0–30 vol% SiC reinforced HfB 2 -based composite. Pressureless sintering process was performed at 2050 °C for 4 h under a vacuum atmosphere. Microstructural studies revealed that in situ SiC reinforcement was formed and distributed in the composite according to the following reaction: Si + C = SiC. A maximum relative density of 98% was measured for the 20 vol% SiC containing HfB 2 composite. Mechanical investigations showed that the hardness and the fracture toughness of these composites were increased and reached up to 21.2 GPa for HfB 2 -30 vol% SiC and 4.9 MPa.m 1/2 for HfB 2 -20 vol% SiC, respectively. Results showed that alpha-SiC reinforcements were created jagged, irregular, and elongated in shape which were in situ formed between HfB 2 grains and filled the porosities. Formation of alpha-SiC contributed to improving the relative density and mechanical properties of the composite samples. By increasing SiC content, an enhanced trend of thermal conductivity was observed as well as a reduced trend for electrical conductivity.