The influence of Ti-induced precipitates on the microstructure and mechanical properties of (Zr,W)C solid solution

The practical applications of ZrC are restricted by its low fracture toughness and resistance to sintering densification. This study reports the in-situ precipitation behavior of (Zr,W)C solid solution precipitates induced by Ti. The (Zr0.7W0.3)C solid solution powder was prepared via carbothermic reduction using pressureless sintering at 2200 °C for 1 h. Varying quantities of TiH2 were reacted with the (Zr0.7W0.3)C matrix, to precipitate the second phase in-situ, via hot-pressing sintering (50 MPa) at 1600 °C for 1 h. When the content of TiH2 was 10 mol%, W and W2C were the second phases precipitated. As the TiH2 concentration increased, the precipitates converted into W2C and the (Ti,Zr)C solid solution. Furthermore, nano-scale dot-like W precipitates gradually increased inside the crystal grains of the (Zr,W,Ti)C matrix. The optimized comprehensive mechanical properties of (Zr,W,Ti)C-based multiphase ceramics were obtained by adding 40 mol% TiH2; the relative density was 99.7%, the Vickers hardness was 24.68 GPa, and the fracture toughness was 5.76 MPa·m1/2. The precipitates (of varying type and concentration) exhibited distinct toughening effects relative to the (Zr,W)C solid solution.