Effect of different additives and open porosity on fracture toughness of ZrB₂–SiC-based composites prepared by SPS

In this work, Taguchi experimental design technique was applied to determine the most influential additives and SPS parameters for optimizing fracture toughness of ZrB₂–SiC based composites. In this case, nine factors (SiC, C_f, MoSi₂, HfB₂ and ZrC content, milling time of C_f and SPS parameters such as temperature, time and pressure) were examined on four different levels in order to obtain the optimum mixture. A total of 32 mixtures were prepared in accordance to the L32 array proposed by the method. Fracture toughness of all composites was measured by single edge-notch beam test. SEM was applied to evaluate microstructure. It has been concluded that the open porosity up to 10% has no significant effect on fracture toughness but in higher values, it is varied inversely with its changes. The results showed that temperature with 34.7% and SiC with 29.7% have significant effect on fracture toughness. C_f, M.t, HfB₂, pressure and time with 2.3%, 3.2%, 0.05%, 0.44% and 2.3% have influence on fracture toughness, respectively. ZrC has 7.8% and MoSi₂ has 6.3% on fracture toughness.