Investigating the effect of SPS parameters on densification and fracture toughness of ZrB2-SiC nanocomposite

In this study, the effect of sintering parameters on densification and fracture toughness of spark plasma sintering ZrB2-SiC nanocomposites was evaluated. For this purpose, ZrB2-30 vol% SiC nanocomposites in the conditions of 1600 degrees C-4 min, 1700 degrees C-4 min, 1800 degrees C-4 min, 1800 degrees C-8 min, 1800 degrees C-12 min were sintered. Scanning Electron Microscopy (SEM) was used in order to investigate the microstructural variations. The bulk density was measured accoring to ASTM C 373-88. Single edge notch beam (SENB) method was used to determine the fracture toughness of samples. Microstructural observations showed that an increase in sintering temperature led to slight increase in SiC grains size but no sensitive variation in ZrB2. However, increasing the sintering time resulted to increase both ZrB2 and SiC grain size. Also, it was found, temperature and time ascent always increases the relative density. In addition, it was concluded that optimal temperature and time to reach the highest fracture toughness are 1800 C and 8 min, respectively. Investigation of SEM images of the Vickers indent and their path propagation showed that the deviation and branching of crack are the most important toughening mechanisms in ZrB2-SiC nanocomposites.