Microstructure and Thermal Shock Resistance of Zr7/8Ti1/8B2-20 vol% SiC Composites Synthesized by Mechanical Alloying and Spark Plasma Sintering

ZrB2-based composites are promising ultra-high temperature materials, nonetheless their poor damage tolerance and low oxidation resistance hinder their practical applications. In the present work, Zr1-xTixB2-20 vol% SiC composites were prepared based on the mechanical alloying (MA) method and spark plasma sintering (SPS) technique. The results showed that solid solution of ZrTiB4 can be obtained by taking nano-sized ZrB2-TiB2 powders from the MA process. The Zr7/8Ti1/8B2-20 vol% SiC composites presented higher fracture toughness due to various toughening mechanisms, such as 'crack deflection' and 'pull out' induced by the finer solid solution particles and nano-sized graphite. Consequently, Zr7/8Ti1/8B2-20 vol% SiC composites possessed a residual strength of 180 MPa after thermal shock test with a temperature difference of 1000 degrees C, while the conventional ZrB2-20 vol% SiC composites only remained at 81.4 MPa.